GB Virus C and Mortality from HIV Infection

To the Editor: The reports of Xiang et al. 1 and Tillmann et al. 2 (Sept. 6 issue) further document that coinfection with the apparently nonpathogenic flavivirus GB virus C (GBV-C, or hepatitis G virus) prolongs survival in patients infected with the human immunodeficiency virus (HIV). As the accompanying editorial 3 emphasizes, there are no causal inferences to be drawn from these observations, and the suggestion that therapy with GBV-C might improve survival among HIV-infected patients is correctly labeled as “premature.” Although viral cross-talk of this sort has been described in a number of other experimental systems, 4 there are other possible explanations for . . .