A SEASONAL INFLUENZA THEORY AND MATHEMATICAL MODEL INCORPORATING METEOROLOGICAL AND SOCIO-BEHAVIORAL FACTORS

On the basis of a comprehensive literature review and data analysis of global influenza surveillance, a transmission theory based numerical model is developed to understand the causative factors of influenza seasonality and the biodynamical mechanisms of seasonal flu. The model is applied to simulate the seasonality and weekly activity of influenza in different areas across all continents and climate zones around the world. Model solution and the good matches between model output and actual influenza indexes affirm that influenza activity is highly auto-correlative and relies on determinants of a broad spectrum. Internal dynamic resonance; variations of meteorological elements (solar radiation, precipitation and dewpoint); socio-behavioral influences and herd immunity to circulating strains prove to be the critical explanatory factors of the seasonality and weekly activity of influenza. In all climate regions, influenza activity is proportional to the exponential of the number of days with precipitation and to the negative exponential of quarter power of sunny hours. Influenza activity is a negative exponential function of dewpoint in temperate and arctic regions and an exponential function of the absolute deviation of dewpoint from its annual mean in the tropics. Epidemics of seasonal influenza could be deemed as the consequence of the dynamic resonance and interactions of determinants. Early interventions (such as opportune vaccination, prompt social distancing, and maintaining incidence well below a baseline) are key to the control and prevention of seasonal influenza. Moderate amount of sunlight exposure or Vitamin D supplementation during rainy and short-day photoperiod seasons, more outdoor activities, and appropriate indoor dewpoint deserve great attention in influenza prevention. To a considerable degree, the study reveals the mechanism of influenza seasonality, demonstrating a potential for influenza activity projection. The concept and algorithm can be explored for further applications.

Epidemiological features of seasonal influenza transmission among 11 climate zones in Chinese mainland

Background Previous studies provided some evidence of meteorological factors influence seasonal influenza transmission patterns varying across regions and latitudes. However, research on seasonal influenza activities based on climate zones are still in lack. This study aims to utilize the ecological-based Koppen Geiger climate zones classification system to compare the spatial and temporal epidemiological characteristics of seasonal influenza in Chinese mainland and assess the feasibility of developing an early warning system.Methods Weekly influenza cases number from 2014 to 2019 at the county and city level were sourced from China National Notifiable Infectious Disease Report Information System. Epidemic temporal indices, time series seasonality decomposition, spatial modelling theories including Moran’s/ and local indicators of spatial association were applied to identify the spatial and temporal patterns of influenza transmission.Results All climate zones had peaks in Winter-Spring season. Arid, desert, cold (BWk) showed up the first peak. Only Tropical, savannah (Aw) and Temperate, dry winter with hot summer (Cwa) zones had unique summer peak. Temperate, no dry season and hot summer (Cfa) zone had highest average incidence rate (IR) at 1.047/100,000. The Global Moran’s/ showed that average IR had significant clustered trend (z = 53.69,P < 0.001), with local Moran’s/ identified high-high cluster in Cfa and Cwa. IR differed among three age groups between climate zones (0-14 years old:F = 26.80,P < 0.001;15-64 years old:F = 25.04,P < 0.001;Above 65 years old:F = 5.27,P < 0.001). Age group 0-14 years had highest average IR in Cwa and Cfa (IR= 6.23 and 6.21) with unique dual peaks in winter and spring season showed by seasonality decomposition.Conclusions Seasonal influenza exhibited distinct spatial and temporal patterns in different climate zones. Seasonal influenza primarily emerged in BWk, subsequently in Cfa and Cwa. Cfa, Cwa and BSk pose high risk for seasonal influenza epidemics. The research finds will provide scientific evidence for developing seasonal influenza early warning system based on climate zones.

Parents＇ Perception and their Decision on their Children＇s Vaccination Against Seasonal Influenza in Guangzhou

Background： Seasonal influenza epidemic occurs every year in Guangzhou, which can affect all age groups. Young children are the most susceptible targets. Parents can decide whether to vaccinate their children or not based on their own consideration in China. The aim of this study was to identify factors that are important for parental decisions on vaccinating their children against seasonal influenza based on a modified health belief model （HBM）. Methods： A cross-sectional study was conducted in Guangzhou, China. A total of 335 parents who had at least on child aged between 6 months and 3 years were recruited from women and children＇s hospital in Guangzhou, China. Each eligible subject was invited for a face-to-face interview based on a standardized questionnaire. Results： Uptake of seasonal influenza within the preceding 12 months among the target children who aged between 6 months and 36 months was 47.7%. Around 62.4% parents indicated as being ＂likely/very likely＂ to take their children for seasonal influenza vaccination in the next 12 months. The hierarchical logistic regression model showed that children＇s age （odds ratio [OR] =2.59, 95% confidence interval [C/I： 1.44-4.68）, social norm （OR = 2.08, 95% CI： 1.06-4.06） and perceived control （OR - 2.96, 95% CI： 1.60-5.50） were significantly and positively associated with children＇s vaccination uptake within the preceding 12 months; children with a history of taking seasonal influenza vaccine （OR = 2.50, 95% CI： 1.31-4.76）, perceived children＇s health status （OR = 3.36, 95% C1： 1.68-6.74）, worry/anxious about their children influenza infection （OR = 2.31, 95% CI： 1.19-4.48） and perceived control （OR = 3.21, 95% CI： 1.65-6.22） were positively association with parental intention to vaccinate their children in the future 12 months. However, anticipated more regret about taking children for the vaccination was associated with less likely to vaccinate children within the preceding 12 months （OR = 0.21, 95% CI： 0.08-0.52）. Conclusions： The modified HBM provided a good theoretical basic for understanding factors associated with parents＇ decisions on their children＇s vaccination against seasonal influenza.

Molecular Epidemiology and Vaccine Compatibility Analysis of Seasonal Influenza Viruses in Wuhan, 2016–2019

Influenza viruses(FLUV)cause high morbidity and mortality annually in the world and pose a serious threat to the public health.Wuhan,as an important transportation hub in China,has a dense population and suitable climate,which also lays a major hidden danger for the outbreak of influenza.To survey and characterize the seasonal FLUV in Wuhan during 2016–2019,we collected 44,738 throat swabs,among which 15.5%were influenza A(FLUAV)positive,6.1%influenza B(FLUBV)and 0.3%co-infection.By monitoring FLUV in each month from June 2016 to May 2019,different with the previously seasonality pattern,only a single influenza peak was appeared in winter of 2017–2018 and 2018–2019,respectively.These data indicated that the complex circulation pattern of seasonal influenza in Wuhan.In addition,we found the age group was skewed towards 5–14 years group whose activity were mostly school based,which suggested school may be an important place for influenza outbreaks.Meanwhile,phylogenic analysis revealed that two subtypes(subclade 3C.2 a2 and 3C.2 a1b)of A(H3N2)were circulating in Wuhan and there was an obvious transition in 2018 because the two subclades were detected simultaneously.Furthermore,by estimating the vaccine effectiveness,we found that the vaccine strain of FLUAV didn’t seem to match very well the current epidemic strain,especially A(H3N2).Hence,more accurate prediction of seasonal outbreak is essential for vaccine design.Taken together,our results provided the current information about seasonal FLUV in Wuhan which form the basis for vaccine updating.

The Epidemiology of Influenza in Children Hospitalized at the Hospital of Sikasso, Mali 2015-2019

Introduction: Influenza is an acute respiratory infectious disease, highly contagious due to influenza viruses. The objective of this work was to identify, understand the epidemiology of circulating strains and estimate disease transmission. Patients and Methods: The study was carried out in the pediatric department of the Sikasso Hospital. This was a prospective, longitudinal descriptive study over a five-year period (January 1, 2015 to December 31, 2019). She was interested in severe acute respiratory infections (SARI) for hospitalized patients in the pediatric department. Results: During the study period the prevalence of severe acute respiratory infections among hospitalized children was 21.85‰. The majority of cases were observed in 2019 with 58 cases, the sex ratio was 1.8. The age group from 0 to 1 was the most represented with 100 cases (48.30%) followed by 2 to 4 years 73 cases (35.24%) and 5 to 15 years 34 cases (16.46%). More than half of the patients lived in rural areas 129 (62.31%). Fever and cough were present in the majority of patients. No children had received influenza vaccination. In study 36 (17.39%) cases were positive for influenza A and B.

Efficacy of seasonal pandemic influenza hemagglutinin DNA vaccines delivered by electroporation against aseasonal H1N1 virus challenge in mice

Prophylactic DNA vaccines against the influenza virus are promising alternatives to conventional vaccines. In this study, we generated two candidate gene-based influenza vaccines encoding either the seasonal or pandemic hemagglutinin antigen （HA） from the strains A/New Caledonia/20/99 （HIN1） （pV1AS） and A/Califorrtia/04/2009 （H1N1） （pVEH1）, respectively. After verifying antigen expression, the immunogenicity of the vaccines delivered intramuscularly with electroporation was tested in a mouse model. Sera of immunized animals were tested in hemagglutination inhibition assays and by ELISA for the presence of HA-specific antibodies. HA-specific T-cells were also measured in IFN-γ ELISpot assays. The protective efficacy of the candidate influenza vaccines was evaluated by measuring mortality rates and body weight after a challenge with 100 LD50 of mouse-adapted A/New Caledonia/20/99 （H1N1）. Mice immunized with either one of the two vaccines showed significantly higher T cell and humoral immune responses （P〈0.05） than the pVAX1 control group. Additionally, the pV1A5 vaccine effec- tively protected the mice against a lethal homologous mouse-adapted virus challenge with a survival rate of 100% compared with a 40% survival rate in the pVEH1 vaccinated group （P〈0.05）. Our study indicates that the seasonal influenza DNA vac- cine completely protects against the homologous A/New Caledonia/20/99 virus （H1N1）, while the pandemic influenza DNA vaccine only partially protects against this virus.

A discrete-time susceptible-infectious-recovered-susceptible model for the analysis of influenza data

We develop a discrete time compartmental model to describe the spread of seasonal influenza virus.As time and disease state variables are assumed to be discrete,this model is considered to be a discrete time,stochastic,Susceptible-Infectious-RecoveredSusceptible(DT-SIRS)model,where weekly counts of disease are assumed to follow a Poisson distribution.We allow the disease transmission rate to also vary over time,and the disease can only be reintroduced after extinction if there is a contact with infected individuals from other host populations.To capture the variability of influenza activities from one season to the next,we define the seasonality with a 4-week period effect that may change over years.We examine three different transmission rates and compare their performance to that of existing approaches.Even though there is limited information for susceptible and recovered individuals,we demonstrate that the simple models for transmission rates effectively capture the behaviour of the disease dynamics.We use a Bayesian approach for inference.The framework is applied in an analysis of the temporal spread of influenza in the province of Manitoba,Canada,2012e2015.