Hepatitis E virus

Discovery history and classification

For a long time, the pathogen was hidden under the term "non-A, non-B hepatitis." The virus was discovered in 1983, marked by an unprecedented scientific step—a self-experiment. Soviet scientist M.S. Balayan and his co-authors used fecal extracts obtained from nine patients with unexplained hepatitis for their research, which allowed them to isolate a new infectious agent.

In modern taxonomy, the pathogen belongs to the family Hepeviridae and is classified into a separate genus, Hepevirus.

Morphology and genome

The pathogen is a simple virion, meaning the complete absence of an outer lipid envelope. It has a spherical shape with a particle diameter ranging from 27 to 34 nm. The protein capsid is organized with icosahedral symmetry.

The viral genetic material is represented by a single-stranded positive-sense RNA molecule (+RNA). This genome encodes several critical viral structures:

• RNA-dependent RNA polymerase (essential for replicating the genetic material);
• Papain-like protease (involved in the maturation of viral proteins);
• Transmembrane protein (performs the key function of viral entry into a susceptible target cell).

Epidemiology

The primary mechanism of transmission is fecal-oral, with the waterborne route of infection (consumption of contaminated drinking water) playing a dominant role. Geographically, the disease is distributed extremely unevenly across the world, although historically there has been a very high frequency of outbreaks in Central Asia.

The source of infection includes not only sick humans. Active circulation of the virus among wild and domestic animals—specifically pigs, cattle, and birds—has been proven. This indicates a pronounced zoonotic potential of the virus, representing the possibility of direct transmission of the pathogen from an infected animal to a human.

Clinical course

The incubation period (the time from infection to the appearance of the first symptoms) lasts from 2 to 6 weeks. The classic clinical picture consists of two main components: general intoxication syndrome and signs of moderate liver damage. Notably, jaundice, which is classic for other types of hepatitis, is significantly less frequent in this form.

Following the infection, lasting immunity is established. For the general population, the prognosis of the disease is considered favorable, but a critical risk group exists.

In pregnant women, the infection can take extremely severe forms. Mortality in this group is not uncommon. The main causes of death are rapidly developing hemorrhagic syndrome and acute renal failure.

Diagnostics, treatment, and prevention

Microbiological diagnosis relies on two main investigative methods:

1. Serological method (ELISA): performed on blood serum or plasma. Detection of specific anti-HEV IgM antibodies confirms the acute phase of the infection. Detection of anti-HEV IgG indicates a past infection and established immunity.
2. Molecular-genetic method (PCR): used in the acute phase to detect viral RNA (HEV RNA). The samples tested are feces and blood serum.

No specific antiviral treatment has been developed. Basic therapy is limited to symptomatic and pathogenetic measures. Special attention is paid to pregnant women: due to the high risk of a severe course, the administration of specific immunoglobulin is indicated.

Nonspecific prevention is based on sanitary and hygienic measures, primarily ensuring the population has access to quality and safe water supplies. For specific prevention, non-live whole-virion vaccines already exist, while recombinant and live vaccines are in the active development stage.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanism of action of the transmembrane protein during HEV cell entry
• Pathogenesis of acute renal failure and hemorrhagic syndrome in pregnant women
• The role of the papain-like protease in the viral replication cycle
• Technology for creating non-live whole-virion hepatitis E vaccines
• Interpretation of ELISA results (dynamics of IgM and IgG) in viral hepatitis

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.