Hepatitis E virus is a leading cause of acute viral hepatitis in the developing world; the clinical features are similar to those caused by other hepatic viruses, hepatitis B and hepatitis C virus. The WHO is estimating an annual infection burden with HEV 1 and 2 with around 20 million cases
, where 3.4 million symptomatic cases
giving rise to 70,000 deaths
and 3,000 still births per year.
However, although the WHO and many others are still referring to above numbers even in 2016, they arise from a global survey on the global distribution of HEV genotypes 1 & 2 in the year 2005, published only in 2012
; therefore this does not take into account the global annual infections of genotype 3 & 4, which are now known to be of zoonotic nature.
No recent updated global data on HEV infection globally are available, however, due to the rapidly rising figures in countries where developed health infrastructure enables accurate and specific diagnosis of disease, a much higher infection- and death rate thus must be assumed.
Today, HEV has reached worldwide distribution, as illustrated by the US Centre for Disease Control and Prevention (see Figure 1: Global distribution of hepatitis E in 2012). Besides highly endemic regions in Asia and Africa, with an infection rate well above ≥ 25% of sporadic non-A non-B hepatitis, virtually all other regions worldwide are regarded as endemic (infection rate ≤ 25% of sporadic non-A non-B hepatitis).
HEV is usually regarded as a self-limiting disease, has an incubation period ranging from 30-60 days, and in most cases is symptomatically indistinguishable from infection with hepatitis A (HAV). Where an HEV infection in immunocompetent people in most cases is self-limiting
, with a mild to moderate disease with a mortality rate of 0.4-4%, this contrasts starkly with infection during pregnancy, where approx. 25% of patients suffer fatal disease, typically within their third trimester
Further high-risk groups include post-transplant patients, immunocompromised patients (e.g. HIV infection) and liver disease patients. Liver disease, specifically non-alcoholic steatosis, remains one of the fastest growing disorders in developed countries, and is most probably linked to dietary factors and lifestyles, and is poised to increase further over the coming decades, highlighting the requirement of prophylaxis and treatment of a viral disease which results in exacerbated and worsening outcomes in those patients.
All of these risk groups of patients show a history of chronicity developing from infection, which leads to unfavourable outcomes and highlights the absence of specific therapeutics for treatment.
Although HEV infection is commonly through the faecal-oral route through consumption of undercooked meats such as pork and venison, much of the infection burden is attributed to poor hygiene and underdeveloped infrastructure such as water sanitation in developing countries. HEV infection has become a global major threat, and the burden of disease, incidence of mortality and morbidity, and importance of the public health challenge posed by HEV infection is now recognised in the developed world, including Europe and USA.