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Robert H. Purcell, Suzanne U. Emerson, Hidden danger: The raw facts about hepatitis E virus, The Journal of Infectious Diseases, Volume 202, Issue 6, 15 September 2010, Pages 819–821, https://doi.org/10.1086/655900
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Extract
In 1980, hepatitis E was the last of the 5 recognized types of human hepatitis to be discovered; in 1990, the genome of the etiologic agent of hepatitis E, hepatitis E virus (HEV), was cloned and serological tests were developed [1]. It proved to be the most or second-most important cause of acute clinical hepatitis among adults throughout much of Asia, the Middle East, and Africa [2]. In contrast, HEV was rarely identified in industrialized countries, and the few reported cases of infection were usually in someone who had recently traveled to an endemic region. In the past few years this pattern has changed, as cases of endemic or autochthonous hepatitis E have been diagnosed with increasing frequency in individuals who have not traveled abroad.
HEV exists as at least 4 genotypes. Genotype 1 is the principal cause of disease in much of Asia, the Middle East, and Africa, whereas genotype 2 is associated with outbreaks in Mexico and Central Africa [2]. In 1998, 2 cases of autochthonous hepatitis E were reported in the United States [3]. These appeared not to have been caused by genotypes 1 or 2. At about the same time, HEV was recovered from domestic swine in the United States, and this virus proved to be closely related to the viruses recovered from the 2 humans in the United States with hepatitis E [3, 4]. These were the first reports of what became known as genotype 3. Eventually, this genotype was recovered from swine herds throughout the Western Hemisphere and parts of Asia and shown to be highly endemic, infecting >90% of swine in some herds [4, 5]. At about the same time, an additional genotype, genotype 4, was recovered from humans in parts of Asia and subsequently from swine in the same regions [6, 7]. Both genotypes 3 and 4 continue to be recovered occasionally from humans with hepatitis E, principally from cases in Asia but also from sporadic cases (mostly genotype 3 infections) in North and South America and Europe [8]. However, genotype 1 and, to a lesser extent, genotype 2 have remained the most important causes of epidemics of hepatitis E in developing countries.
