DELTA HEPATITIS (HEPATITIS D)
Delta hepatitis is caused by the hepatitis D virus. This small single-stranded RNA virus requires the presence of hepatitis B surface antigens for its transmission and is thus found only in persons with acute or chronic hepatitis B infection. Strategies directed at prevent-ing hepatitis B are also effective in preventing delta hepatitis. The method of replication of hepatitis D viral RNA is not clear. Associated with the RNA are proteins of 27 and 29 kilodaltons that constitute the delta antigen. This protein–RNA complex is surrounded by HBsAg (Fig 37–5). Thus, although the delta virus produces its own antigens, it co-opts the HBsAg in assembling its coat.
Delta hepatitis is most prevalent in groups at high risk of hepatitis B. Injection drug users are those at greatest risk in the western parts of the world, and as many as 50% of such individuals may have IgG antibody to the delta virus antigen. Other risks include dialysis. Nonparenteral and vertical transmission can also occur.