Transmission of Hepatitis E Virus in Developing Countries

Abstract

Hepatitis E virus (HEV), an RNA virus of the Hepeviridae family, has marked heterogeneity. While all five HEV genotypes can cause human infections, genotypes HEV-1 and -2 infect humans alone, genotypes HEV-3 and -4 primarily infect pigs, boars and deer, and genotype HEV-7 primarily infects dromedaries. The global distribution of HEV has distinct epidemiological patterns based on ecology and socioeconomic factors. In resource-poor countries, disease presents as large-scale waterborne epidemics, and few epidemics have spread through person-to-person contact; however, endemic diseases within these countries can potentially spread through person-to-person contact or fecally contaminated water and foods. Vertical transmission of HEV from infected mother to fetus causes high fetal and perinatal mortality. Other means of transmission, such as zoonotic transmission, can fluctuate depending upon the region and strain of the virus. For instance, zoonotic transmission can sometimes play an insignificant role in human infections, such as in India, where human and pig HEV infections are unrelated. However, recently China and Southeast Asia have experienced a zoonotic spread of HEV-4 from pigs to humans and this has become the dominant mode of transmission of hepatitis E in eastern China. Zoonotic HEV infections in humans occur by eating undercooked pig flesh, raw liver, and sausages; through vocational contact; or via pig slurry, which leads to environmental contamination of agricultural products and seafood. Lastly, blood transfusion-associated HEV infections occur in many countries and screening of donors for HEV RNA is currently under serious consideration. To summarize, HEV genotypes 1 and 2 cause epidemic and endemic diseases in resource poor countries, primarily spreading through contaminated drinking water. HEV genotypes 3 and 4 on the other hand, cause autochthonous infections in developed, and many developing countries, by means of a unique zoonotic food-borne transmission.

Changing Epidemiology of Hepatitis A and Hepatitis E Viruses in China, 1990–2014

“…Although we did not have data on HEV genotypes for this study, it is possible that the change in age distribution of hepatitis E patients may result from the shift of the prevalent HEV genotype in China from genotype 1 to genotype 4 (and, to a lesser extent, genotype 3). Genotype 3 and genotype 4 are known to infect older men (14,15). The increase in the number of HEV infections in eastern China (online Technical Appendix Figure 1) could also be caused by this genotype shift and improved surveillance in these more developed provinces (15), rather than by true geographic heterogeneity in risk factors.…”

Changing Epidemiology of Hepatitis A and Hepatitis E Viruses in China, 1990–2014

“…Although we did not have data on HEV genotypes for this study, it is possible that the change in age distribution of hepatitis E patients may result from the shift of the prevalent HEV genotype in China from genotype 1 to genotype 4 (and, to a lesser extent, genotype 3). Genotype 3 and genotype 4 are known to infect older men ( 14 , 15 ). The increase in the number of HEV infections in eastern China (Technical Appendix Figure 1) could also be caused by this genotype shift and improved surveillance in these more developed provinces ( 15 ), rather than by true geographic heterogeneity in risk factors.…”

Seroprevalence and incidence of hepatitis E virus among blood donors: A review

“…Similarly, HEV‐5 and HEV‐6 are novel genotypes identified in wild boar in Japan . HEV‐7, a newly discovered HEV genotype, primarily infects dromedary camels (Arabian 1‐humped camels) and was identified in the UAE very recently . According to the CDC, large HEV epidemics have been reported in Asia, the Middle East, Africa, and Central America .…”