AIM:A drcannual variation in the onset of several acute diseases, mostly dealing with cardiovascular system,has been reported. The present study was to verify the possible existence of a seasonal variability in the on...AIM:A drcannual variation in the onset of several acute diseases, mostly dealing with cardiovascular system,has been reported. The present study was to verify the possible existence of a seasonal variability in the onset of acute pancreatitis. METHODS:All patients consecutively admitted to the Hospital of Ferrara,Italy,between January 1998 to December 2002, whose discharge diagnosis was acute pancreatitis,were considered.According to the time of admission,cases were categorized into twelve 1-mo intervals and in four periods by season.x^2 test for goodness of fit and partial Fourier series were used for statistical analysis. RESULTS:During the study period,549 cases of acute pancreatitis were observed.A significant peak of higher incidence was found in March-May,both for total population, males and subgroups with and without cholelithiasis or alcoholism.Fourier analysis showed the existence of a circannual rhythmic pattern with its main peak in March(95% CL.:February-April,P=0.005),and a secondary one in September.Death occurred more frequently in December- February,compared to the other periods(P=0.029),and chronobiologic analysis yielded a seasonal peak in November- December(P<0.001). CONCLUSION:This study shows the existence of a circannual variation in the onset of acute pancreatitis,with a significantly higher frequency of events in the spring,especially for patients with cholelithiasis or alcoholism.Moreover,events occurring during the colder months seem to be characterized by a higher mortality rate.展开更多
Objective: To analyze the trends of incidence rate and age at diagnosis for cervical cancer incidence in China using population-based cancer registration data from 2000 to 2014. Methods: Data were from National Cent...Objective: To analyze the trends of incidence rate and age at diagnosis for cervical cancer incidence in China using population-based cancer registration data from 2000 to 2014. Methods: Data were from National Central Cancer Registry of China. Crude incidence rates (CIRs), age-specific incidence rate, age-standardized incidence rates (ASIRs), age percentage distribution, standardized age percentage distribution, mean age at diagnosis and standardized mean age at diagnosis for cervical cancer in all areas of China, urban China and rural China were calculated separately. The world Segi's population was applied to remove the age structure influence. Joinpoint regression was performed to obtain average annual percent change (AAPC) and age- period-cohort analysis was used to examine the incidence trends. Results: CIRs and ASIRs for cervical cancer increased in China from 2000 to 2014. The AAPC of ASIRs in China was at 9.2% [95% confidence interval (95% CI): 7.0%-I 1.5%, P〈0.05], and the AAPC in rural areas was relatively high. The age-specific incidence rate in groups aged 0-69 years have significantly increased over time. Groups aged 40-69 years showed the highest incidence risk, and the annual percent changes (APCs) of incidence rate in groups aged 40-59 years in urban China and groups aged 0-49 years in rural China were more than 10%. For each age group, the urban-to-rural incidence rate ratios (IRRs) got close to 1 over time. There were clear birth cohort effects in successive generations born from 1940 to 1970 in China. In rural China, the standardized mean age at diagnosis had significantly declined by 5.18 years. In China, the main peak and secondary peak of standardized age percentages appeared in the groups aged 45-49 and 40-44 years, respectively. In rural China, the main peak of standardized age percentage moved from the group aged 55-59 years to the group aged 45-49 years, and the standardized age percentages of groups aged 25-34 years also increased. In China, the standardized age percentages has significantly increased in groups aged 35-64 and 30-64 years over time, and accounted for about 80% and 85% in 2014, respectively. Conclusions: The cervical cancer incidence increased in China and the gap of incidence between urban and rural China was narrowed. The trends of increasing cervical cancer incidence among younger women existed in China, especially in rural China. A more appropriate screening, vaccination and health education strategies should be established.展开更多
BACKGROUND The global epidemiology of type 1 diabetes(T1D)is not yet well known,as no precise data are available from many countries.T1D is,however,characterized by an important variation in incidences among countries...BACKGROUND The global epidemiology of type 1 diabetes(T1D)is not yet well known,as no precise data are available from many countries.T1D is,however,characterized by an important variation in incidences among countries and a dramatic increase of these incidences during the last decades,predominantly in younger children.In the United States and Europe,the increase has been associated with the gross domestic product(GDP)per capita.In our previous systematic review,geographical variation of incidence was correlated with socio-economic factors.AIM To investigate variation in the incidence of T1D in age categories and search to what extent these variations correlated with the GDP per capita.METHODS A systematic review was performed to retrieve information about the global incidence of T1D among those younger than 14 years of age.The study was carried out according to the PRISMA recommendations.For the analysis,the incidence was organized in the periods:1975-1999 and 2000-2017.We searched the incidence of T1D in the age-groups 0-4,5-9 and 10-14.We compared the incidences in countries for which information was available for the two periods.We obtained the GDP from the World Bank.We analysed the relationship between the incidence of T1D with the GDP in countries reporting data at the national level.RESULTS We retrieved information for 84 out of 194 countries around the world.We found a wide geographic variation in the incidence of T1D and a worldwide increase during the two periods.The largest contribution to this increase was observed in the youngest group of children with T1D,with a relative increase of almost double when comparing the two periods(P value=2.5×e-5).Twenty-six countries had information on the incidence of T1D at the national level for the two periods.There was a positive correlation between GDP and the incidence of T1D in both periods(Spearman correlation=0.52 from 1975-1999 and Spearman correlation=0.53 from 2000-2017).CONCLUSION The incidence increase was higher in the youngest group(0-4 years of age),and the highest incidences of T1D were found in wealthier countries.展开更多
AIM:An investigation into inflammatory bowel disease and colorectal cancer in Veszprem Province was conducted from 1977 to 2001.METHODS: Both hospital and outpatient records were collected and reviewed comprehensively...AIM:An investigation into inflammatory bowel disease and colorectal cancer in Veszprem Province was conducted from 1977 to 2001.METHODS: Both hospital and outpatient records were collected and reviewed comprehensively. The majority of patients were followed up regularly.RESULTS:The population of the province was decreased from 386000 to 376000 during the period. Five hundred sixty new cases of ulcerative colitis (UC), 212 of Crohn's disease (CD), and 40 of indeterminate colitis (IC) were diagnosed. The incidence rates increased from 1.66 to 11.01 cases per 100 000 persons for UC, from 0.41 to 4.68 for CD and from 0.26 to 0.74 for IC. The prevalence rate at the end of 2001 was 142.6 for UC and 52.9 cases per 100 000 persons for CD. The peak onset age in UC patients was between 30 and 40 years, in CD between 20 and 30 years. A family history of IBD was present in 3.4% in UC and 9.9% in CD patients.Smoking increased the risk for CD (OR=1.94) while it decreased the risk for UC (OR=0.25). Twelve colorectal carcinomas were observed in this cohort, the cumulative colorectal cancer risk after 10 years in UC was 2%, after 20 years 8.8%, after 30 years 13.3%.CONCLUSION:The incidence and prevalence rates of IBD have increased steadily in Veszprem Province, now equivalent to that in Western European countries. Rapid increase in incidence rates supports a probable role for environmental factors. The rate of colorectal cancers in IBD is similar to that observed in Western countries.展开更多
AIM:To study the clinical and epidemiological features of patients with clonorchiasis so as to provide scientific evidences for the diagnosis and prevention of clonorchiasis. METHODS:Stools from 282 subjects suspected...AIM:To study the clinical and epidemiological features of patients with clonorchiasis so as to provide scientific evidences for the diagnosis and prevention of clonorchiasis. METHODS:Stools from 282 subjects suspected of having clonorchiasis were examined for helminth eggs with modified Kato's thick smear and sedimentation methods,and their sera were tested for HAV-DNA,HBV-DNA,HCV-RNA,HDV- RNA and HEV-RNA with polymerase chain reaction (PCR). Clinical symptoms of patients with clonorchiasis only were analyzed,and their blood samples were tested for circulating antigen (CAg) with Dot-ELISA,esoinophilic granulocyte count, and alanine aminotransferase (ALT).Meanwhile,they were asked to provide data of occupation,eating habit,hygienic habit and knowledge of donorchiasis.In addition,the ecosystem of the environment in epidemic areas was surveyed. RESULTS:Among the 282 patients,61 (21.43%) were infected with clonorchis sinensis only,97 (34.64%) were co-infected with clonorchis sinensis and other pathogens, 92 (32.86%) were infected with hepatitis virus only and 31 (11.07%) neither with clonorchis sinensis nor hepatitis virus. Among the 61 patients with clonorchiasis only,there were 14 (22.95%) subjects with discomfort over hepatic region or epigasfrium,12 (19.67%) with general malaise or discomfort and inertia in total body,6 (9.84%) with anorexia,indigestion and nausea,4 (6.56%) with fever,dizziness and headache (6.56%),and 25 (40.98%) without any symptoms;sixty one (100%) with CAg (+),98.33% (59160) with eosinophilic granulocytes increased and 65.00% (39/60) with ALT increased.B-mode ultrasonography revealed 61 cases with dilated and thickened walls of intrahepatic bile duct,and blurred patchy echo acoustic image in liver.Twenty-six cases had stones in the bile duct,39 cases had slightly enlarged liver with diffuse coarse spots in liver parenchyma.Twenty cases had enlarged gallbladder with thickened coarse wall and image of floating plagues,9 cases had slightly enlarged spleen.By analysis of epidemiological data,we found that the ecologic environment was favorable for the epidemiology of clonorchiasis.Most patients with clonorchiasis were lack of knowledge about the disease.Their living environment, hygienic habits,eating habits and their occupations were the related factors that caused the prevalence of the disease. CONCLUSION:The clinical symptoms of clonorchiasis are non-specific,and the main evidences for diagnosis of clonorchiasis should be provided by etiologic examination, B-mode ultrasonography and clinical history.The infection of clonorchis sinensis is related to occupations,bad eating habits and lack of knowledge about prevention of the disease.展开更多
AIM:It is known that toxoplasmosis rarely leads to various liver pathologies,most common of which is granulomatose hepatitis in patients having normal immune systems.Patients who have cirrhosis of the liver are subjec...AIM:It is known that toxoplasmosis rarely leads to various liver pathologies,most common of which is granulomatose hepatitis in patients having normal immune systems.Patients who have cirrhosis of the liver are subject to a variety of cellular as well as humoral immunity disorders.Therefore,it may be considered that toxoplasmosis can cause more frequent and more severe diseases in patients with cirrhosis and is capable of changing the course of the disease.The aim of this study was to investigate the frequency of toxoplasmosis in patients with cirrhosis. METHODS:Serum samples were taken from 108 patients with cirrhosis under observation in the Hepatology Polyclinic of the Gastroenterology Clinic,and a control group made up of 50 healthy blood donors.IFAT and ELISA methods were used to investigate the IgG and IgM antibodies,which had developed from these sera. RESULTS:Toxoplasma IgG and IgN antibody positivity was found in 74 (68.5%) of the 108 cirrhotic patients and 24 (48%) of the 50 people in the control group.The difference between them was significant (P<0.05). CONCLUSION:In conclusion,it was found that the toxopiasma sero-prevalence in the cirrhotic patients in this study was higher.Cirrhotic patients are likely to form a toxoplasma risk group.More detailed studies are needed on this subject.展开更多
AIM:To study the epidemiology of gastric malignancies in Jordan as a model for Middle East countries where such data is scarce. METHODS:Pertinent epidemiological and clinicopathological data for 201 patients with gast...AIM:To study the epidemiology of gastric malignancies in Jordan as a model for Middle East countries where such data is scarce. METHODS:Pertinent epidemiological and clinicopathological data for 201 patients with gastric malignancy in north of Jordan between 1991 and 2001 were analyzed. RESULTS:Male:female ratio was 1.8:1.The mean age was 61.2 years,and 8.5% of the patients were younger than 40 years of age.The overall age-adjusted incidence was 5.82/100 000 population/year.The age specific incidence for males raised from 1.48 in those aged 30-39 years to 72.4 in those aged 70-79 years.Adenocarcinomas, gastric lymphomas,malignant stromal tumors,and carcinoids were found in 87.5%,8%,2.5%,and 2% respectively.There was an average of 10.1-month delay between the initial symptoms and the diagnosis.Only 82 patients underwent“curative”gastrectomy.Among adenocarcinoma groups,Lauren intestinal type was the commonest(72.2%)and the distal third was the most common localization(48.9%).The mean follow up for patients with gastric adenocarcinoma was 25.1 mo(range 1-132mo).The 5-year survival rates for stages Ⅰ(n=15), Ⅱ(n=41),Ⅲ(n=59),and Ⅳ(n=53) were 67.3%,41.3%, 5.7%,and 0% respectively(P=0.0001).The overall 5 year survival was 21.1%. CONCLUSION:Despite low inddence,some epidemiological features of gastric cancer in Jordan mimic those of high- risk areas.Patients are detected and treated after a relatively long delay.No justification in favor of a possible gastric cancer screening effort in Jordan is supported by our study;rather,the need of an earlier diagnosis and subsequent better care.展开更多
AIM: To assess the role of thyroid disease as a risk for fractures in Crohn's patients.METHODS: A cross-sectional study was conducted from 1998 to 2000. The study group consisted of 210 patients with Crohn's d...AIM: To assess the role of thyroid disease as a risk for fractures in Crohn's patients.METHODS: A cross-sectional study was conducted from 1998 to 2000. The study group consisted of 210 patients with Crohn's disease. A group of 206 patients without inflammatory bowel disease served as controls. Primary outcome was thyroid disorder. Secondary outcomes included use of steroids, immunosuppressive medications, surgery and incidence of fracture.RESULTS: The prevalence of hyperthyroidism was similar in both groups. However, the prevalence of hypothyroidism was lower in Crohn's patients (3.8 % vs 8.2 %, P=0.05).Within the Crohn's group, the use of immunosuppressive agents (0 % vs11 %), steroid usage (12.5 % vs37 %), small bowel surgery (12.5 % vs 28 %) and large bowel surgery (12.5 % vs27 %) were lower in the hypothyroid subset as compared to the euthyroid subset. Seven (3.4 %) Crohn'spatients suffered fracture, all of whom were euthyroid.CONCLUSION: Thyroid disorder was not found to be associated with Crohn's disease and was not found to increase the risk for fractures. Therefore, screening for thyroid disease is not a necessary component in the management of Crohn's disease.展开更多
AIM:Both observational and experimental studies have shown that higher selenium status reduces the risk of upper gastrointestinal cancers in selenium deficient populations. Recent cancer registry data have shown very ...AIM:Both observational and experimental studies have shown that higher selenium status reduces the risk of upper gastrointestinal cancers in selenium deficient populations. Recent cancer registry data have shown very different rates of esophageal cancer(EC)and gastric cancer(GC)in four Provinces of Iran,namely Ardabil,Mazandaran,Golestan, and Kerman.The aim of this study was to have a preliminary assessment of the hypothesis that high rates of EC in Golestan and high rates of GC in Ardabil may be partly attributable to selenium deficiency. METHODS:We measured serum selenium in 300 healthy adults from An:labil(n=100),Mazandaran(n=50),Golestan (n=100),and Kerman(n=50),using inductively coupled plasma,with dynamic reaction cell,mass spectrometry(ICP- DRC-MS)at the US Centers for Disease Control(Atlanta, Georgia). RESULTS:The median serum selenium concentrations were very different in the four Provinces.The medians(IQR)for selenium in Ardabil,Mazandarn,Golestan,and Kerman were 82(75-94),123(111-132),155(141-173),and 119 (110-128)μg/L,respectively(P<0.001).The results of linear regression showed that the Province variable,by itself, explained 76% of the variance in log selenium(r^2=0.76). The proportion of the populations with a serum selenium more than 90 μg/L(the concentration at which serum selenoproteins are saturated)was 100% in Golestan, Kerman,and Mazandaran but only 29% in Ardabil. CONCLUSION:Our findings suggest that selenium defidency is not a major contributor to the high incidence of EC seen in northeastern Iran,but it may play a role in the high incidence of GC in Ardabil Province. Nouarie M,Pourshams A,Kamangar F,Sotoudeh M,Derakhshan MH,Akbari MR,Fakheri H,Zahedi MJ,Caldwell K,Abner CC, Taylor PR,Malekzadeh R,Dawsey SM.Ecologic study of serum展开更多
Background: Epilepsy accounts for a significant portion of the global disease burden. However, little is known about the disease burden of epilepsy in China and its provinces. Methods: We assessed the burden of epilep...Background: Epilepsy accounts for a significant portion of the global disease burden. However, little is known about the disease burden of epilepsy in China and its provinces. Methods: We assessed the burden of epilepsy in China and its provinces, municipalities, and autonomous regions from 1990 to 2019. Burden was measured as incidence, prevalence, deaths, years lived with disability, years of life lost, and disability-adjusted life years (DALYs), by age, sex, year, and province. We used the Socio-Demographic Index (SDI) to determine the association between the provincial development level and age-standardized DALY rates of epilepsy from 1990 to 2019. Results: In 2019, epilepsy caused 1367.51 thousand (95% uncertainty interval [UI]: 979.92–1837.61 thousand) DALYs, and the age-standardized DALY rate was 99.77 (95% UI: 71.33–133.52)/100,000. The age-standardized incidence and prevalence rates for epilepsy in China were 24.65/100,000 and 219.69/100,000, increased by 45.00% (95% UI: 8.03–98.74%) and 35.72% (95% UI: 0.47–86.19%) compared with that in 1990, respectively. From 1990 to 2019, the proportion of DALY caused by epilepsy in the age group under 25 years steadily decreased. The proportion of DALYs caused by epilepsy in people aged 50 years and over increased from 9.45% and 10.22% in 1990 to 29.01% and 32.72% for male and female individuals in 2019, respectively. The highest age-standardized mortality rates were seen in Tibet (4.26 [95% UI: 1.43–5.66]/100,000), Qinghai (1.80 [95% UI: 1.15–2.36]/100,000), and Yunnan (1.30 [95% UI: 0.88–1.62]/100,000), and the lowest mortality rates were in Guangdong (0.48 [95% UI: 0.39–0.64]/100,000), Zhejiang (0.56 [95% UI: 0.44–0.70]/100,000), and Shanghai (0.57 [95% UI: 0.41–0.73]/100,000). The age-standardized DALY rates across the country and in provinces, municipalities, and autonomous regions generally decreased as their SDI increased. Conclusions: The disease burden of epilepsy is still heavy in China, especially in the western provinces. The incidence and prevalence of epilepsy increased between 1990 and 2019, and the burden of epilepsy in the elderly increases gradually. This study provides evidence on epilepsy prevention and care of different regions in China.展开更多
Background:Neuroendocrine neoplasms(NENs)are rare tumors characterized by variable biology and delayed diagnosis.However,the nationwide epidemiology of NENs has never been reported in China.We aimed to estimate the in...Background:Neuroendocrine neoplasms(NENs)are rare tumors characterized by variable biology and delayed diagnosis.However,the nationwide epidemiology of NENs has never been reported in China.We aimed to estimate the incidence and survival statistics of NENs in China,in comparison to those in the United States during the same period.Methods:Based on the data from 246 population-based cancer registries covering 272.5 million people of China,we calculated age-specific incidence on NENs in 2017 and multiplied by corresponding national population to estimate the nationwide incidence in China.The data of 22 population-based cancer registries were used to estimate the trends of NENs incidence from 2000 to 2017 through the Joinpoint regression model.We used the cohort approach to analyze the 5-year age-standardized relative survival by sex,age group,and urban-rural area between 2008 and 2013,based on data from 176 high-quality cancer registries.We used data from the Surveillance,Epidemiology,and End Results(SEER)18 program to estimate the comparable incidence and survival of NENs in the United States.Results:The overall age-standardized rate(ASR)of NENs incidence was lower in China(1.14 per 100,000)than in the United States(6.26 per 100,000).The most common primary sites were lungs,pancreas,stomach,and rectum in China.The ASRs of NENs incidence increased by 9.8%and 3.6%per year in China and the United States,respectively.The overall 5-year relative survival in China(36.2%)was lower than in the United States(63.9%).The 5-year relative survival was higher for female patients than male patients,and was higher in urban areas than in rural areas.Conclusions:The disparities in burden of NENs persist across sex,area,age group,and site in China and the United States.These findings may provide a scientific basis on prevention and control of NENs in the two countries.展开更多
AIM: To study the salient features of colorectal cancer(CRC) in Libya.METHODS: Patients records were gathered at the primary oncology clinic in eastern Libya for the period of one calendar year(2012). Using this data,...AIM: To study the salient features of colorectal cancer(CRC) in Libya.METHODS: Patients records were gathered at the primary oncology clinic in eastern Libya for the period of one calendar year(2012). Using this data, various parameters were analyzed and age-standardized incidence rates were determined using the direct method and the standard population.RESULTS: During 2012, 174 patients were diagnosed with CRC, 51.7%(n = 90) male and 48.3%(n = 84) females. The average age was 58.7(± 13.4) years, with men around 57.3(± 13) years old and women usually 60.1(± 13.8) years of age. Libya has the highest rate of CRC in North Africa, with an incidence closer to the European figures. The age-standardized rate for CRC was 17.5 and 17.2/100000 for males and females respectively. It was the second most common cancer, forming 19% of malignancies, with fluctuation in ranking and incidence in different cities/villages. Increasingly, younger ages are being afflicted and a higher proportion of patients are among the > 40 years subset.Nearly two-thirds presented at either stage Ⅲ(22.4%) or Ⅳ(38.4%).CONCLUSION: Cancer surveillance systems should be established in order to effectively monitor the situation. Likewise, screening programs are invaluable in the Libyan scenario given the predominance of sporadic cases.展开更多
Background::China and the United States(US)ranked first and third in terms of new liver cancer cases and deaths globally in 2020.Therefore,a comprehensive assessment of trends in the incidence of primary liver cancer ...Background::China and the United States(US)ranked first and third in terms of new liver cancer cases and deaths globally in 2020.Therefore,a comprehensive assessment of trends in the incidence of primary liver cancer with four major etiological factors between China and the US during the past 30 years with age-period-cohort(APC)analyses is warranted.Methods::Data were obtained from the Global Burden of Disease 2019,and period/cohort relative risks were estimated by APC modeling from 1990 to 2019.Results::In 2019,there were 211,000 new liver cancer cases in China and 28,000 in the US,accounting for 39.4%and 5.2%of global liver cancer cases,respectively.For China,the age-standardized incidence rate(ASIR)consecutively decreased before 2005 but increased slightly since then,whereas the ASIR continuously increased in the US.Among the four etiological factors of liver cancer,the fastest reduction in incidence was observed in hepatitis B virus-related liver cancer among Chinese women,and the fastest increase was in nonalcoholic steatosis hepatitis(NASH)-related liver cancer among American men.The greatest reduction in the incidence of liver cancer was observed at the age of 53 years in Chinese men(-5.2%/year)and 33 years in Chinese women(-6.6%/year),while it peaked at 58 years old in both American men and women(4.5%/year vs.2.8%/year).Furthermore,the period risks of alcohol-and NASH-related liver cancer among Chinese men have been elevated since 2013.Simultaneously,leveled-off period risks were observed in hepatitis C viral-related liver cancer in both American men and women.Conclusions::Currently,both viral and lifestyle factors have been and will continue to play an important role in the time trends of liver cancer in both countries.More tailored and efficient preventive strategies should be designed to target both viral and lifestyle factors to prevent and control liver cancer.展开更多
Objective: To predict the daily incidence and fatality rates based on long short-term memory(LSTM) in 4 age groups of COVID-19 patients in Mazandaran Province, Iran.Methods: To predict the daily incidence and fatality...Objective: To predict the daily incidence and fatality rates based on long short-term memory(LSTM) in 4 age groups of COVID-19 patients in Mazandaran Province, Iran.Methods: To predict the daily incidence and fatality rates by age groups, this epidemiological study was conducted based on the LSTM model. All data of COVID-19 disease were collected daily for training the LSTM model from February 22, 2020 to April 10, 2021 in the Mazandaran University of Medical Sciences. We defined 4 age groups, i.e., patients under 29, between 30 and 49, between 50 and 59, and over 60 years old. Then, LSTM models were applied to predict the trend of daily incidence and fatality rates from 14 to 40 days in different age groups. The results of different methods were compared with each other.Results: This study evaluated 5 0826 patients and 5 109 deaths with COVID-19 daily in 20 cities of Mazandaran Province. Among the patients, 25 240 were females(49.7%), and 25 586 were males(50.3%). The predicted daily incidence rates on April 11, 2021 were 91.76, 155.84, 150.03, and 325.99 per 100 000 people, respectively;for the fourteenth day April 24, 2021, the predicted daily incidence rates were 35.91, 92.90, 83.74, and 225.68 in each group per 100 000 people. Furthermore, the predicted average daily incidence rates in 40 days for the 4 age groups were 34.25, 95.68, 76.43, and 210.80 per 100 000 people, and the daily fatality rates were 8.38, 4.18, 3.40, 22.53 per 100 000 people according to the established LSTM model. The findings demonstrated the daily incidence and fatality rates of 417.16 and 38.49 per 100 000 people for all age groups over the next 40 days. Conclusions: The results highlighted the proper performance of the LSTM model for predicting the daily incidence and fatality rates. It can clarify the path of spread or decline of the COVID-19 outbreak and the priority of vaccination in age groups.展开更多
In this paper, we propose an age-structured viral infection model with general incidence function that takes account of the loss of viral particles due to their absorption into susceptible cells. The proposed model is...In this paper, we propose an age-structured viral infection model with general incidence function that takes account of the loss of viral particles due to their absorption into susceptible cells. The proposed model is described by partial differential and ordinary differential equations. We first show that the model is mathematically and biologically well-posed. Furthermore, the uniform persistence and the global behavior of the model are investigated. Moreover, the age-structured models and results presented in many previous studies are improved and generalized.展开更多
Saturating contact rate of individual contacts is crucial in an epidemiology model. A mathematical SIR model with saturation incidence and age of infection is formulated in this paper. In addition, we study the dynami...Saturating contact rate of individual contacts is crucial in an epidemiology model. A mathematical SIR model with saturation incidence and age of infection is formulated in this paper. In addition, we study the dynamical behavior of this model and define the basic reproductive number R0. The authors also prove that the diseased-free equilibrium is globally asymptotically stable if R0 〈 1. The endemic equilibrium is locally asymptotically stable if K1 〉 α and R0 〉 1.展开更多
基金Supported by a Research Grant"ex-60%" From the University of Ferrara
文摘AIM:A drcannual variation in the onset of several acute diseases, mostly dealing with cardiovascular system,has been reported. The present study was to verify the possible existence of a seasonal variability in the onset of acute pancreatitis. METHODS:All patients consecutively admitted to the Hospital of Ferrara,Italy,between January 1998 to December 2002, whose discharge diagnosis was acute pancreatitis,were considered.According to the time of admission,cases were categorized into twelve 1-mo intervals and in four periods by season.x^2 test for goodness of fit and partial Fourier series were used for statistical analysis. RESULTS:During the study period,549 cases of acute pancreatitis were observed.A significant peak of higher incidence was found in March-May,both for total population, males and subgroups with and without cholelithiasis or alcoholism.Fourier analysis showed the existence of a circannual rhythmic pattern with its main peak in March(95% CL.:February-April,P=0.005),and a secondary one in September.Death occurred more frequently in December- February,compared to the other periods(P=0.029),and chronobiologic analysis yielded a seasonal peak in November- December(P<0.001). CONCLUSION:This study shows the existence of a circannual variation in the onset of acute pancreatitis,with a significantly higher frequency of events in the spring,especially for patients with cholelithiasis or alcoholism.Moreover,events occurring during the colder months seem to be characterized by a higher mortality rate.
基金supported by Program Grant in Fundamental Research from the Ministry of Science and Technology(No.2014FY121100)Chinese Academy of Medical Sciences(CAMS)Innovation Fund for Medical Sciences(No.201612M2004)
文摘Objective: To analyze the trends of incidence rate and age at diagnosis for cervical cancer incidence in China using population-based cancer registration data from 2000 to 2014. Methods: Data were from National Central Cancer Registry of China. Crude incidence rates (CIRs), age-specific incidence rate, age-standardized incidence rates (ASIRs), age percentage distribution, standardized age percentage distribution, mean age at diagnosis and standardized mean age at diagnosis for cervical cancer in all areas of China, urban China and rural China were calculated separately. The world Segi's population was applied to remove the age structure influence. Joinpoint regression was performed to obtain average annual percent change (AAPC) and age- period-cohort analysis was used to examine the incidence trends. Results: CIRs and ASIRs for cervical cancer increased in China from 2000 to 2014. The AAPC of ASIRs in China was at 9.2% [95% confidence interval (95% CI): 7.0%-I 1.5%, P〈0.05], and the AAPC in rural areas was relatively high. The age-specific incidence rate in groups aged 0-69 years have significantly increased over time. Groups aged 40-69 years showed the highest incidence risk, and the annual percent changes (APCs) of incidence rate in groups aged 40-59 years in urban China and groups aged 0-49 years in rural China were more than 10%. For each age group, the urban-to-rural incidence rate ratios (IRRs) got close to 1 over time. There were clear birth cohort effects in successive generations born from 1940 to 1970 in China. In rural China, the standardized mean age at diagnosis had significantly declined by 5.18 years. In China, the main peak and secondary peak of standardized age percentages appeared in the groups aged 45-49 and 40-44 years, respectively. In rural China, the main peak of standardized age percentage moved from the group aged 55-59 years to the group aged 45-49 years, and the standardized age percentages of groups aged 25-34 years also increased. In China, the standardized age percentages has significantly increased in groups aged 35-64 and 30-64 years over time, and accounted for about 80% and 85% in 2014, respectively. Conclusions: The cervical cancer incidence increased in China and the gap of incidence between urban and rural China was narrowed. The trends of increasing cervical cancer incidence among younger women existed in China, especially in rural China. A more appropriate screening, vaccination and health education strategies should be established.
基金Supported by doctoral scholarship (Natalia Gomez-Lopera) from Colciencias,No.727
文摘BACKGROUND The global epidemiology of type 1 diabetes(T1D)is not yet well known,as no precise data are available from many countries.T1D is,however,characterized by an important variation in incidences among countries and a dramatic increase of these incidences during the last decades,predominantly in younger children.In the United States and Europe,the increase has been associated with the gross domestic product(GDP)per capita.In our previous systematic review,geographical variation of incidence was correlated with socio-economic factors.AIM To investigate variation in the incidence of T1D in age categories and search to what extent these variations correlated with the GDP per capita.METHODS A systematic review was performed to retrieve information about the global incidence of T1D among those younger than 14 years of age.The study was carried out according to the PRISMA recommendations.For the analysis,the incidence was organized in the periods:1975-1999 and 2000-2017.We searched the incidence of T1D in the age-groups 0-4,5-9 and 10-14.We compared the incidences in countries for which information was available for the two periods.We obtained the GDP from the World Bank.We analysed the relationship between the incidence of T1D with the GDP in countries reporting data at the national level.RESULTS We retrieved information for 84 out of 194 countries around the world.We found a wide geographic variation in the incidence of T1D and a worldwide increase during the two periods.The largest contribution to this increase was observed in the youngest group of children with T1D,with a relative increase of almost double when comparing the two periods(P value=2.5×e-5).Twenty-six countries had information on the incidence of T1D at the national level for the two periods.There was a positive correlation between GDP and the incidence of T1D in both periods(Spearman correlation=0.52 from 1975-1999 and Spearman correlation=0.53 from 2000-2017).CONCLUSION The incidence increase was higher in the youngest group(0-4 years of age),and the highest incidences of T1D were found in wealthier countries.
文摘AIM:An investigation into inflammatory bowel disease and colorectal cancer in Veszprem Province was conducted from 1977 to 2001.METHODS: Both hospital and outpatient records were collected and reviewed comprehensively. The majority of patients were followed up regularly.RESULTS:The population of the province was decreased from 386000 to 376000 during the period. Five hundred sixty new cases of ulcerative colitis (UC), 212 of Crohn's disease (CD), and 40 of indeterminate colitis (IC) were diagnosed. The incidence rates increased from 1.66 to 11.01 cases per 100 000 persons for UC, from 0.41 to 4.68 for CD and from 0.26 to 0.74 for IC. The prevalence rate at the end of 2001 was 142.6 for UC and 52.9 cases per 100 000 persons for CD. The peak onset age in UC patients was between 30 and 40 years, in CD between 20 and 30 years. A family history of IBD was present in 3.4% in UC and 9.9% in CD patients.Smoking increased the risk for CD (OR=1.94) while it decreased the risk for UC (OR=0.25). Twelve colorectal carcinomas were observed in this cohort, the cumulative colorectal cancer risk after 10 years in UC was 2%, after 20 years 8.8%, after 30 years 13.3%.CONCLUSION:The incidence and prevalence rates of IBD have increased steadily in Veszprem Province, now equivalent to that in Western European countries. Rapid increase in incidence rates supports a probable role for environmental factors. The rate of colorectal cancers in IBD is similar to that observed in Western countries.
文摘AIM:To study the clinical and epidemiological features of patients with clonorchiasis so as to provide scientific evidences for the diagnosis and prevention of clonorchiasis. METHODS:Stools from 282 subjects suspected of having clonorchiasis were examined for helminth eggs with modified Kato's thick smear and sedimentation methods,and their sera were tested for HAV-DNA,HBV-DNA,HCV-RNA,HDV- RNA and HEV-RNA with polymerase chain reaction (PCR). Clinical symptoms of patients with clonorchiasis only were analyzed,and their blood samples were tested for circulating antigen (CAg) with Dot-ELISA,esoinophilic granulocyte count, and alanine aminotransferase (ALT).Meanwhile,they were asked to provide data of occupation,eating habit,hygienic habit and knowledge of donorchiasis.In addition,the ecosystem of the environment in epidemic areas was surveyed. RESULTS:Among the 282 patients,61 (21.43%) were infected with clonorchis sinensis only,97 (34.64%) were co-infected with clonorchis sinensis and other pathogens, 92 (32.86%) were infected with hepatitis virus only and 31 (11.07%) neither with clonorchis sinensis nor hepatitis virus. Among the 61 patients with clonorchiasis only,there were 14 (22.95%) subjects with discomfort over hepatic region or epigasfrium,12 (19.67%) with general malaise or discomfort and inertia in total body,6 (9.84%) with anorexia,indigestion and nausea,4 (6.56%) with fever,dizziness and headache (6.56%),and 25 (40.98%) without any symptoms;sixty one (100%) with CAg (+),98.33% (59160) with eosinophilic granulocytes increased and 65.00% (39/60) with ALT increased.B-mode ultrasonography revealed 61 cases with dilated and thickened walls of intrahepatic bile duct,and blurred patchy echo acoustic image in liver.Twenty-six cases had stones in the bile duct,39 cases had slightly enlarged liver with diffuse coarse spots in liver parenchyma.Twenty cases had enlarged gallbladder with thickened coarse wall and image of floating plagues,9 cases had slightly enlarged spleen.By analysis of epidemiological data,we found that the ecologic environment was favorable for the epidemiology of clonorchiasis.Most patients with clonorchiasis were lack of knowledge about the disease.Their living environment, hygienic habits,eating habits and their occupations were the related factors that caused the prevalence of the disease. CONCLUSION:The clinical symptoms of clonorchiasis are non-specific,and the main evidences for diagnosis of clonorchiasis should be provided by etiologic examination, B-mode ultrasonography and clinical history.The infection of clonorchis sinensis is related to occupations,bad eating habits and lack of knowledge about prevention of the disease.
文摘AIM:It is known that toxoplasmosis rarely leads to various liver pathologies,most common of which is granulomatose hepatitis in patients having normal immune systems.Patients who have cirrhosis of the liver are subject to a variety of cellular as well as humoral immunity disorders.Therefore,it may be considered that toxoplasmosis can cause more frequent and more severe diseases in patients with cirrhosis and is capable of changing the course of the disease.The aim of this study was to investigate the frequency of toxoplasmosis in patients with cirrhosis. METHODS:Serum samples were taken from 108 patients with cirrhosis under observation in the Hepatology Polyclinic of the Gastroenterology Clinic,and a control group made up of 50 healthy blood donors.IFAT and ELISA methods were used to investigate the IgG and IgM antibodies,which had developed from these sera. RESULTS:Toxoplasma IgG and IgN antibody positivity was found in 74 (68.5%) of the 108 cirrhotic patients and 24 (48%) of the 50 people in the control group.The difference between them was significant (P<0.05). CONCLUSION:In conclusion,it was found that the toxopiasma sero-prevalence in the cirrhotic patients in this study was higher.Cirrhotic patients are likely to form a toxoplasma risk group.More detailed studies are needed on this subject.
文摘AIM:To study the epidemiology of gastric malignancies in Jordan as a model for Middle East countries where such data is scarce. METHODS:Pertinent epidemiological and clinicopathological data for 201 patients with gastric malignancy in north of Jordan between 1991 and 2001 were analyzed. RESULTS:Male:female ratio was 1.8:1.The mean age was 61.2 years,and 8.5% of the patients were younger than 40 years of age.The overall age-adjusted incidence was 5.82/100 000 population/year.The age specific incidence for males raised from 1.48 in those aged 30-39 years to 72.4 in those aged 70-79 years.Adenocarcinomas, gastric lymphomas,malignant stromal tumors,and carcinoids were found in 87.5%,8%,2.5%,and 2% respectively.There was an average of 10.1-month delay between the initial symptoms and the diagnosis.Only 82 patients underwent“curative”gastrectomy.Among adenocarcinoma groups,Lauren intestinal type was the commonest(72.2%)and the distal third was the most common localization(48.9%).The mean follow up for patients with gastric adenocarcinoma was 25.1 mo(range 1-132mo).The 5-year survival rates for stages Ⅰ(n=15), Ⅱ(n=41),Ⅲ(n=59),and Ⅳ(n=53) were 67.3%,41.3%, 5.7%,and 0% respectively(P=0.0001).The overall 5 year survival was 21.1%. CONCLUSION:Despite low inddence,some epidemiological features of gastric cancer in Jordan mimic those of high- risk areas.Patients are detected and treated after a relatively long delay.No justification in favor of a possible gastric cancer screening effort in Jordan is supported by our study;rather,the need of an earlier diagnosis and subsequent better care.
文摘AIM: To assess the role of thyroid disease as a risk for fractures in Crohn's patients.METHODS: A cross-sectional study was conducted from 1998 to 2000. The study group consisted of 210 patients with Crohn's disease. A group of 206 patients without inflammatory bowel disease served as controls. Primary outcome was thyroid disorder. Secondary outcomes included use of steroids, immunosuppressive medications, surgery and incidence of fracture.RESULTS: The prevalence of hyperthyroidism was similar in both groups. However, the prevalence of hypothyroidism was lower in Crohn's patients (3.8 % vs 8.2 %, P=0.05).Within the Crohn's group, the use of immunosuppressive agents (0 % vs11 %), steroid usage (12.5 % vs37 %), small bowel surgery (12.5 % vs 28 %) and large bowel surgery (12.5 % vs27 %) were lower in the hypothyroid subset as compared to the euthyroid subset. Seven (3.4 %) Crohn'spatients suffered fracture, all of whom were euthyroid.CONCLUSION: Thyroid disorder was not found to be associated with Crohn's disease and was not found to increase the risk for fractures. Therefore, screening for thyroid disease is not a necessary component in the management of Crohn's disease.
文摘AIM:Both observational and experimental studies have shown that higher selenium status reduces the risk of upper gastrointestinal cancers in selenium deficient populations. Recent cancer registry data have shown very different rates of esophageal cancer(EC)and gastric cancer(GC)in four Provinces of Iran,namely Ardabil,Mazandaran,Golestan, and Kerman.The aim of this study was to have a preliminary assessment of the hypothesis that high rates of EC in Golestan and high rates of GC in Ardabil may be partly attributable to selenium deficiency. METHODS:We measured serum selenium in 300 healthy adults from An:labil(n=100),Mazandaran(n=50),Golestan (n=100),and Kerman(n=50),using inductively coupled plasma,with dynamic reaction cell,mass spectrometry(ICP- DRC-MS)at the US Centers for Disease Control(Atlanta, Georgia). RESULTS:The median serum selenium concentrations were very different in the four Provinces.The medians(IQR)for selenium in Ardabil,Mazandarn,Golestan,and Kerman were 82(75-94),123(111-132),155(141-173),and 119 (110-128)μg/L,respectively(P<0.001).The results of linear regression showed that the Province variable,by itself, explained 76% of the variance in log selenium(r^2=0.76). The proportion of the populations with a serum selenium more than 90 μg/L(the concentration at which serum selenoproteins are saturated)was 100% in Golestan, Kerman,and Mazandaran but only 29% in Ardabil. CONCLUSION:Our findings suggest that selenium defidency is not a major contributor to the high incidence of EC seen in northeastern Iran,but it may play a role in the high incidence of GC in Ardabil Province. Nouarie M,Pourshams A,Kamangar F,Sotoudeh M,Derakhshan MH,Akbari MR,Fakheri H,Zahedi MJ,Caldwell K,Abner CC, Taylor PR,Malekzadeh R,Dawsey SM.Ecologic study of serum
文摘Background: Epilepsy accounts for a significant portion of the global disease burden. However, little is known about the disease burden of epilepsy in China and its provinces. Methods: We assessed the burden of epilepsy in China and its provinces, municipalities, and autonomous regions from 1990 to 2019. Burden was measured as incidence, prevalence, deaths, years lived with disability, years of life lost, and disability-adjusted life years (DALYs), by age, sex, year, and province. We used the Socio-Demographic Index (SDI) to determine the association between the provincial development level and age-standardized DALY rates of epilepsy from 1990 to 2019. Results: In 2019, epilepsy caused 1367.51 thousand (95% uncertainty interval [UI]: 979.92–1837.61 thousand) DALYs, and the age-standardized DALY rate was 99.77 (95% UI: 71.33–133.52)/100,000. The age-standardized incidence and prevalence rates for epilepsy in China were 24.65/100,000 and 219.69/100,000, increased by 45.00% (95% UI: 8.03–98.74%) and 35.72% (95% UI: 0.47–86.19%) compared with that in 1990, respectively. From 1990 to 2019, the proportion of DALY caused by epilepsy in the age group under 25 years steadily decreased. The proportion of DALYs caused by epilepsy in people aged 50 years and over increased from 9.45% and 10.22% in 1990 to 29.01% and 32.72% for male and female individuals in 2019, respectively. The highest age-standardized mortality rates were seen in Tibet (4.26 [95% UI: 1.43–5.66]/100,000), Qinghai (1.80 [95% UI: 1.15–2.36]/100,000), and Yunnan (1.30 [95% UI: 0.88–1.62]/100,000), and the lowest mortality rates were in Guangdong (0.48 [95% UI: 0.39–0.64]/100,000), Zhejiang (0.56 [95% UI: 0.44–0.70]/100,000), and Shanghai (0.57 [95% UI: 0.41–0.73]/100,000). The age-standardized DALY rates across the country and in provinces, municipalities, and autonomous regions generally decreased as their SDI increased. Conclusions: The disease burden of epilepsy is still heavy in China, especially in the western provinces. The incidence and prevalence of epilepsy increased between 1990 and 2019, and the burden of epilepsy in the elderly increases gradually. This study provides evidence on epilepsy prevention and care of different regions in China.
文摘Background:Neuroendocrine neoplasms(NENs)are rare tumors characterized by variable biology and delayed diagnosis.However,the nationwide epidemiology of NENs has never been reported in China.We aimed to estimate the incidence and survival statistics of NENs in China,in comparison to those in the United States during the same period.Methods:Based on the data from 246 population-based cancer registries covering 272.5 million people of China,we calculated age-specific incidence on NENs in 2017 and multiplied by corresponding national population to estimate the nationwide incidence in China.The data of 22 population-based cancer registries were used to estimate the trends of NENs incidence from 2000 to 2017 through the Joinpoint regression model.We used the cohort approach to analyze the 5-year age-standardized relative survival by sex,age group,and urban-rural area between 2008 and 2013,based on data from 176 high-quality cancer registries.We used data from the Surveillance,Epidemiology,and End Results(SEER)18 program to estimate the comparable incidence and survival of NENs in the United States.Results:The overall age-standardized rate(ASR)of NENs incidence was lower in China(1.14 per 100,000)than in the United States(6.26 per 100,000).The most common primary sites were lungs,pancreas,stomach,and rectum in China.The ASRs of NENs incidence increased by 9.8%and 3.6%per year in China and the United States,respectively.The overall 5-year relative survival in China(36.2%)was lower than in the United States(63.9%).The 5-year relative survival was higher for female patients than male patients,and was higher in urban areas than in rural areas.Conclusions:The disparities in burden of NENs persist across sex,area,age group,and site in China and the United States.These findings may provide a scientific basis on prevention and control of NENs in the two countries.
文摘AIM: To study the salient features of colorectal cancer(CRC) in Libya.METHODS: Patients records were gathered at the primary oncology clinic in eastern Libya for the period of one calendar year(2012). Using this data, various parameters were analyzed and age-standardized incidence rates were determined using the direct method and the standard population.RESULTS: During 2012, 174 patients were diagnosed with CRC, 51.7%(n = 90) male and 48.3%(n = 84) females. The average age was 58.7(± 13.4) years, with men around 57.3(± 13) years old and women usually 60.1(± 13.8) years of age. Libya has the highest rate of CRC in North Africa, with an incidence closer to the European figures. The age-standardized rate for CRC was 17.5 and 17.2/100000 for males and females respectively. It was the second most common cancer, forming 19% of malignancies, with fluctuation in ranking and incidence in different cities/villages. Increasingly, younger ages are being afflicted and a higher proportion of patients are among the > 40 years subset.Nearly two-thirds presented at either stage Ⅲ(22.4%) or Ⅳ(38.4%).CONCLUSION: Cancer surveillance systems should be established in order to effectively monitor the situation. Likewise, screening programs are invaluable in the Libyan scenario given the predominance of sporadic cases.
基金The study was sponsored by research grants from the National Natural Science Foundation of China(Nos.81773454 and 82073573)Discipline Construction Funding of Public Health and Preventive Medicine from PekingUniversity Health Science Center(No.BMU2020XY010).
文摘Background::China and the United States(US)ranked first and third in terms of new liver cancer cases and deaths globally in 2020.Therefore,a comprehensive assessment of trends in the incidence of primary liver cancer with four major etiological factors between China and the US during the past 30 years with age-period-cohort(APC)analyses is warranted.Methods::Data were obtained from the Global Burden of Disease 2019,and period/cohort relative risks were estimated by APC modeling from 1990 to 2019.Results::In 2019,there were 211,000 new liver cancer cases in China and 28,000 in the US,accounting for 39.4%and 5.2%of global liver cancer cases,respectively.For China,the age-standardized incidence rate(ASIR)consecutively decreased before 2005 but increased slightly since then,whereas the ASIR continuously increased in the US.Among the four etiological factors of liver cancer,the fastest reduction in incidence was observed in hepatitis B virus-related liver cancer among Chinese women,and the fastest increase was in nonalcoholic steatosis hepatitis(NASH)-related liver cancer among American men.The greatest reduction in the incidence of liver cancer was observed at the age of 53 years in Chinese men(-5.2%/year)and 33 years in Chinese women(-6.6%/year),while it peaked at 58 years old in both American men and women(4.5%/year vs.2.8%/year).Furthermore,the period risks of alcohol-and NASH-related liver cancer among Chinese men have been elevated since 2013.Simultaneously,leveled-off period risks were observed in hepatitis C viral-related liver cancer in both American men and women.Conclusions::Currently,both viral and lifestyle factors have been and will continue to play an important role in the time trends of liver cancer in both countries.More tailored and efficient preventive strategies should be designed to target both viral and lifestyle factors to prevent and control liver cancer.
文摘Objective: To predict the daily incidence and fatality rates based on long short-term memory(LSTM) in 4 age groups of COVID-19 patients in Mazandaran Province, Iran.Methods: To predict the daily incidence and fatality rates by age groups, this epidemiological study was conducted based on the LSTM model. All data of COVID-19 disease were collected daily for training the LSTM model from February 22, 2020 to April 10, 2021 in the Mazandaran University of Medical Sciences. We defined 4 age groups, i.e., patients under 29, between 30 and 49, between 50 and 59, and over 60 years old. Then, LSTM models were applied to predict the trend of daily incidence and fatality rates from 14 to 40 days in different age groups. The results of different methods were compared with each other.Results: This study evaluated 5 0826 patients and 5 109 deaths with COVID-19 daily in 20 cities of Mazandaran Province. Among the patients, 25 240 were females(49.7%), and 25 586 were males(50.3%). The predicted daily incidence rates on April 11, 2021 were 91.76, 155.84, 150.03, and 325.99 per 100 000 people, respectively;for the fourteenth day April 24, 2021, the predicted daily incidence rates were 35.91, 92.90, 83.74, and 225.68 in each group per 100 000 people. Furthermore, the predicted average daily incidence rates in 40 days for the 4 age groups were 34.25, 95.68, 76.43, and 210.80 per 100 000 people, and the daily fatality rates were 8.38, 4.18, 3.40, 22.53 per 100 000 people according to the established LSTM model. The findings demonstrated the daily incidence and fatality rates of 417.16 and 38.49 per 100 000 people for all age groups over the next 40 days. Conclusions: The results highlighted the proper performance of the LSTM model for predicting the daily incidence and fatality rates. It can clarify the path of spread or decline of the COVID-19 outbreak and the priority of vaccination in age groups.
基金We are very grateful and thank the handling editor and the referees for their helpful comments which led to important improvements in our original paper. Research of the author Yu Yang was supported by National Natural Science Foundation of China (No. 11501519).
文摘In this paper, we propose an age-structured viral infection model with general incidence function that takes account of the loss of viral particles due to their absorption into susceptible cells. The proposed model is described by partial differential and ordinary differential equations. We first show that the model is mathematically and biologically well-posed. Furthermore, the uniform persistence and the global behavior of the model are investigated. Moreover, the age-structured models and results presented in many previous studies are improved and generalized.
基金the National Natural Sciences Foundation of China (10471040)the University Foundation of Yuncheng University (20060218)
文摘Saturating contact rate of individual contacts is crucial in an epidemiology model. A mathematical SIR model with saturation incidence and age of infection is formulated in this paper. In addition, we study the dynamical behavior of this model and define the basic reproductive number R0. The authors also prove that the diseased-free equilibrium is globally asymptotically stable if R0 〈 1. The endemic equilibrium is locally asymptotically stable if K1 〉 α and R0 〉 1.