Hepatitis E virus (HEV) is a waterborne disease mainly found in areas with poor sanitation and it is typically transmitted by ingesting fecal matter in contaminated water supplies. The disease is usually acute but can be particularly dangerous in pregnant women.
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Hepatitis E (HEV)
Hepatitis E (HEV) infection has a clinical course comparable to Hepatitis A and it is mostly a self-limiting disease with low death rates. However, in individuals with a weakened immune system, there is a high risk of developing chronic hepatitis. In addition, in pregnant women (particularity those in the third trimester), the disease can be severe with a death rate of 25% and it is often associated with a clinical syndrome called fulminant liver failure. HEV was once an understudied and neglected virus. However, in recent years it has gained awareness due to concern around the safety of blood products with respect to HEV.
There are four main genotypes of HEV: genotypes 1 and 2 have been found only in humans and genotypes 3 and 4 are linked to zoonotic transmission (pigs, wild boar and deer) and cause sporadic infections in industrialized countries through ingestion of undercooked animal meat. Structurally, HEV is a nonenveloped virus with a genome consisting of three open reading frames (ORFs). ORF1, which encodes the nonstructural proteins (NS) necessary for replication, ORF2 which encodes the core protein for the viral capsid, and ORF3 which partially overlaps ORF1 and encodes a viroporin-like protein.
The commonly used tests for HEV infection are IgM and IgG anti-HEV antibody assays and molecular assays. HEV IgM antibodies appear early (from 1-4 weeks) in the course of illness and disappear over 4–5 months. Assays detecting anti-HEV are usually qualitative sandwich immunoassays developed with recombinant HEV antigens that provide a broad coverage of all 4 major HEV genotypes. The antigens typically represent part of the ORF2 and ORF3 proteins and studies have shown that assays based on open reading frame 2 (ORF2) can be more sensitive than those based on ORF3. Simultaneous assessment of anti-HEV IgA has been recommended to improve specificity as the IgM assay may cross-react with other IgM-based assays such as rheumatoid factor IgM. Overall recombinant protein-based tests have demonstrated an ability to detect anti-HEV in 90 to 95% of symptomatic HEV cases.
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