Hepatitis E virus (HEV) is the major etiologic agent of enterically transmiited non-A, non-B hepatitis worldwide and has a high case-fatality rate in pregnant women. Both IgM and IgG antibody to HEV (anti-HEV) are produced following infection. The titer of IgM anti-HEV declines rapidly during early convalescence; IgG anti-HEV persists and appears to provide at least short-term protection against disease.