Epidemic non-A, non-B hepatitis in patients from Pakistan.

Epidemic non-A, non-B hepatitis was diagnosed in three young Pakistani men during a 10-month period at the Los Angeles County-University of Southern California Medical Center. All three patients had recently visited or lived in Karachi, Pakistan. None had serologic markers of hepatitis B virus infection or IgM antibody (acute-phase) to hepatitis A virus. A liver biopsy from one patient showed marked cholestasis and cholangiolar transformation of hepatocytes, a pattern previously described in patients with epidemic non-A, non-B hepatitis. Immune electron microscopy of a stool specimen obtained from this patient 10 days after the onset of symptoms showed virus-like particles, 27 nm in diameter, that were specifically aggregated by antibody contained in acute-phase sera from the three Pakistani patients, from patients with non-A, non-B hepatitis in Burma and Nepal, and from an experimentally infected marmoset. Recognition of three separate cases of probable epidemic-type non-A, non-B hepatitis in patients at one institution during such a short time suggests that Pakistan is endemic for this infection and that the disease may be more commonly spread to the United States than is now presumed.