Hepatitis E, a (relatively) little-known virus
Of all the types of hepatitis that have been characterised up until now, hepatitis “E” is undoubtedly the least well known among both the general public and scientists. While it sometimes causes death, it is asymptomatic in the majority of cases. In industrialised countries, it affects humans but above all, it affects animals, especially pigs. Is it really the same virus? And who infects who? How is it transmitted? The laboratory of veterinary virology at the University of Liège, led by Etienne Thiry, is endeavouring to answer these questions.
Most people have already heard of hepatitis A, B or C. However, very few people are familiar with the different forms of hepatitis beyond the first three letters of the alphabet. For instance, there is hepatitis D, which is quite virulent but mostly unknown to the general public because it develops in the shadow of hepatitis B, from which it is indissociable. But the list doesn’t end here because there is a new addition to this virus family: hepatitis E. A recent arrival that is completely unknown. At least on this side of the planet. In Asia and developing countries, it has made much more of a name for itself. According to the World Health Organisation (WHO), this disease causes the majority of the 20 million new infections and 3.3 million acute cases recorded every year in these countries.
In Belgium, as in other industrialised countries, hepatitis E is present but its incidence is probably under-estimated. Few scientific studies have been carried out on the subject, and few public authorities have subsidised this type of research. Undoubtedly because the infection it causes is far less devastating than those of its “cousins”: 56,600 deaths recorded very year compared with 780,000 for B and 500,000 for C, according to the WHO.
Almost everywhere in Europe, however, researchers are starting to cotton on to this theme. In Belgium, this is the case at the Institut Scientifique de Santé Publique (ISP - Public Health Scientific Institute), which is a reference laboratory in terms of human hepatitis viruses, but also… the faculty of veterinary medicine at ULg. How come? “It may well seem strange that vets are involved in this human disease”, admits Étienne Thiry, director of the Laboratory of Veterinary Virology and Viral Animal Diseases. “This is where the international "One Health" concept comes in, which aims to explore the interactions between animal and human diseases when they are transmitted to humans. Like bird flu for instance”.
In the beginning, everyone thought that hepatitis E was only transmitted from human to human by the faecal-oral route, mainly through contaminated water. But then doubts were raised. What if animals were responsible for it? Was it a human virus or an animal virus?
It all depends on which genotype we are talking about. Hepatitis E has four different genotypes. 1 and 2 only infect humans, mainly in Asia and Africa. They cause severe illness, which is particularly aggressive in pregnant women and can lead to death. On the other hand, 3 and 4 seem to be more inoffensive, with far less serious clinical signs. Genotype 3 is found in humans, mainly in Europe and North America. In Belgium, a study carried out in Flanders (but on a restricted sample) showed that 14 % of people were infected.