Subclinical hepatitis E virus genotype 1 infection:The concept of“dynamic human reservoir”

Hepatitis E virus(HEV)is hyperendemic in South Asia and Africa accounting for half of total Global HEV burden.There are eight genotypes of HEV.Among them,the four common ones known to infect humans,genotypes 1 and 2 are prevalent in the developing world and genotypes 3 and 4 are causing challenge in the industrialized world.Asymptomatic HEV viremia in the general population,especially among blood donors,has been reported in the literature worldwide.The clinical implications related to this asymptomatic viremia are unclear and need further exploration.Detection of viremia due to HEV genotype 1 infection,apparently among healthy blood donors is also reported without much knowledge about its infection rate.Similarly,while HEV genotype 3 is known to be transmitted via blood transfusion in humans and has been subjected to screening in many European nations,instances of transmission have also been documented albeit without significant clinical consequences.Epidemiology of HEV genotype 1 in endemic areas often show waxing and waning pattern.Occasional sporadic occurrence of HEV infection interrupted by outbreaks have been frequently seen.In absence of known animal reservoir,where HEV exists in between outbreak is a mystery that needs further exploration.However,occurrence of asymptomatic HEV viremia due to HEV genotype 1 during epidemiologically quiescent period may explain that this phenomenon may act as a dynamic reservoir.Since HEV genotype 1 infection cannot cause chronicity,subclinical transient infection and transmission of virus might be the reason it sustains in interepidemic period.This might be the similar phenomenon with SARS COVID-19 corona virus infection which is circulating worldwide in distinct phases with peaks and plateaus despite vaccination against it.In view of existing evidence,we propose the concept of“Dynamic Human Reservoir.”Quiescent subclinical infection of HEV without any clinical consequences and subsequent transmission may contribute to the existence of the virus in a community.The potential for transmitting HEV infection by asymptomatic HEV infected individuals by fecal shedding of virus has not been reported in literature.This missing link may be a key to Pandora's box in understanding epidemiology of HEV infection in genotype 1 predominant region.

Modeling the Prevalence of Asymptomatic COVID-19 Infections in the Chinese Mainland

Recently,considerable efforts have been focused on intensifying the screening process for asymptomatic COVID-19 cases in the ChineseMainland,especially for up to 10 million citizens living in Wuhan City by nucleic acid testing.However,a high percentage of domestic asymptomatic cases did not develop into symptomatic ones,which is abnormal and has drawn considerable public attention.Here,we aimed to investigate the prevalence of COVID-19 infections in the Chinese Mainland from a statistical perspective,as it is of referential significance for other regions.By conservatively assuming a development time lag from pre-symptomatic(i.e.,referring to the infected cases that were screened before the COVID-19 symptom onset)to symptomatic as an incubation time of 5.2 days,our results indicated that 92.5%of those tested in Wuhan City,China,and 95.1%of those tested in the Chinese Mainland should have COVID-19 syndrome onset,which was extremely higher than their corresponding practical percentages of 0.8%and 3.3%,respectively.We propose that a certain false positive rate may exist if large-scale nucleic acid screening tests for asymptomatic cases are conducted in common communities with a low incidence rate.Despite adopting relatively high-sensitivity,high-specificity detection kits,we estimated a very low prevalence of COVID-19 infections,ranging from 10
6 to 10
4 in both Wuhan City and the Chinese Mainland.Thus,the prevalence rate of asymptomatic infections in China had been at a very low level.Furthermore,given the lower prevalence of the infection,close examination of the data for false positive results is necessary to minimize social and economic impacts.

Seroprevalence of dengue among healthy adults in a rural community in Southern Malaysia:a pilot study

Background:The frequency and magnitude of dengue epidemics continue to increase exponentially in Malaysia,with a shift in the age range predominance toward adults and an expansion to rural areas.Despite this,information pertaining to the extent of transmission of dengue virus(DENV)in the rural community is lacking.This communitybased pilot study was conducted to establish DENV seroprevalence amongst healthy adults in a rural district in Southern Malaysia,and to identify influencing factors.Methods:In this study undertaken between April and May 2015,a total of 277 adult participants were recruited from households across three localities in the Sungai Segamat subdistrict in Segamat district.Sera were tested for immunoglobulin G(IgG)(Panbio®Dengue Indirect IgG ELISA/high-titer capture)and immunoglobulin M(IgM)(Panbio®)antibodies.The plaque reduction neutralization test(PRNT)was conducted on random samples of IgGpositive sera for further confirmation.Medical history and a recall of previous history of dengue were collected through interviews,whereas sociodemographic information was obtained from an existing database.Results:The overall seroprevalence for DENV infection was 86.6%(240/277)(95%CI:83-91%).Serological evidence of recent infection(IgM/high-titer capture IgG)was noted in 11.2%(31/277)of participants,whereas there was evidence of past infection in 75.5%(209/277)of participants(indirect IgG minus recent infections).The PRNT assay showed that the detected antibodies were indeed specific to DENV.The multivariate analysis showed that the older age group was significantly associated with past DENV infections.Seropositivity increased with age;48.5%in the age group of<25 years to more than 85%in age group of>45 years(P<0.001).No associations with occupation,study site,housing type,comorbidity,educational level,and marital status were observed,although the latter two were statistically significant in the univariate analysis.None of the studied factors were significantly associated with recent DENV infections in the multivariate analysis,although there was a pattern suggestive of recent outbreak in two study sites populated predominately by Chinese people.The majority of infections did not give rise to recognizable disease(either asymptomatic or nonspecific symptoms)as only 12.9%of participants(31/240)recalled having dengue in the past.Conclusions:The predominantly rural community under study had a very high previous exposure to dengue.The finding of a high proportion of unreported cases possibly due to subclinical infections underscores the need for enhanced surveillance and control methods.This finding also has implications for measuring disease burden,understanding transmission dynamics,and hypothesizing effects on DENV vaccine efficacy and uptake.