hepatitis E

Hepatitis E is endemic in developing regions with poor sanitation (South Asia, Africa, Central America) and is a major cause of waterborne hepatitis outbreaks. Genotypes 1 and 2 are associated with epidemic waterborne transmission in endemic areas and affect humans only, while genotypes 3 and 4 are zoonotic (pigs, deer, wild boar) and cause sporadic cases in developed countries, often via undercooked pork or shellfish.

Pathophysiology: After fecal-oral entry, HEV replicates in hepatocytes, leading to direct cytopathic and immune-mediated liver injury similar to other acute viral hepatitides. Incubation period is typically 3-8 weeks.

Clinical features: Most infections are asymptomatic or mild and self-limited, presenting with fatigue, nausea, jaundice, dark urine, and elevated transaminases (AST/ALT), similar to hepatitis A. Chronic infection can occur in immunocompromised patients (e.g., transplant recipients, HIV) with genotype 3, potentially progressing to cirrhosis. Extrahepatic manifestations include neurological complications (Guillain-Barré syndrome, neuralgic amyotrophy) and renal disease.

Key high-yield point: Unlike other hepatitis viruses, HEV infection during pregnancy—particularly in the third trimester—is associated with fulminant hepatic failure and significantly increased maternal and fetal mortality, likely due to hormonal and immunological changes affecting viral replication and host response.

Diagnosis: Detection of anti-HEV IgM (acute infection) and IgG (past exposure/immunity), and HEV RNA by PCR for confirmation, especially in immunocompromised or chronic cases.

Management: Supportive care for acute self-limited disease. Ribavirin is used for chronic infection in immunocompromised hosts. No specific antiviral is approved for acute cases. A recombinant vaccine (HEV 239, Hecolin) is licensed in China but not widely available elsewhere.

Prevention: Ensuring clean water supplies and proper sanitation is the primary preventive measure in endemic regions; avoiding undercooked pork/game meat is key in developed countries.