Abstract
In developing countries, the waterborne transmission of hepatitis E virus (HEV), caused by HEV genotypes 1 (HEV-1) and 2 (HEV-2), leads to the onset of large recurrent outbreaks. HEV infections are of particular concern among pregnant women, due to very high mortality rates (up to 70%). Unfortunately, good understanding of the factors that trigger the occurrence of HEV epidemics is currently lacking; therefore, anticipating the onset of an outbreak is yet not possible. In order to map the geographical regions at higher risk of HEV epidemics and the conditions most favorable for the transmission of the virus, we compiled a dataset of HEV waterborne outbreaks and used it to obtain models of geographical suitability for HEV across the planet. The main three variables that best predict the geographical distribution of HEV outbreaks at global scale are population density, annual potential evapotranspiration and precipitation seasonality. At a regional scale, the temporal occurrence of HEV outbreaks in the Ganges watershed is negatively correlated with the discharge of the river (r = −0.77). Combined, our findings suggest that ultimately, population density and water balance are main parameters influencing the occurrence of HEV-1 and HEV-2 outbreaks. This study expands the current understanding of the combination of factors shaping the biogeography and seasonality of waterborne viral pathogens such as HEV-1 and HEV-2, and contributes to developing novel concepts for the prediction and control of human waterborne viruses in the near future.
Highlights
Hepatitis E virus (HEV) is recognized as one of the most important agents of acute viral hepatitis worldwide[1]
The final dataset used in this study contains 59 geo-referenced outbreaks of waterborne hepatitis E virus (HEV)
27% of all reports of water-related outbreaks caused by HEV genotypes 1 (HEV-1) and HEV-2 have occurred in the north of India (Ganges Valley)
Summary
Hepatitis E virus (HEV) is recognized as one of the most important agents of acute viral hepatitis worldwide[1]. While in industrialized countries HEV infections normally lead to sporadic zoonotic or foodborne cases of acute hepatitis, in developing regions HEV causes large recurrent outbreaks affecting several hundred to several thousand persons[2]. Hot and dry months may possibly decrease the level of surface water leading to an increased concentration of enteric pathogens[16] These observations suggest that climatic factors may be of major importance for the efficient transmission of HEV-1 and HEV-2 and the occurrence of outbreaks. The maximum entropy method (MaxEnt) developed by Philips and colleagues a decade ago[22] is one of the most widely used This method exclusively relies on the use of presence data of a species of interest along with a set of environmental variables to model the speciesgeographical distribution. MaxEnt has shown to perform better than other SDMs25–27 and, unlike other software, it has been previously used in environmental virology to predict the distribution of multiple pathogens[28,29]
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