HIV Infectivity—the Hepatitis B Lesson

Abstract

The probability of acquiring an HIV infection through different types of risk behaviour is not well known. For prognoses on the future spread of the infection some knowledge of these probabilities is of vital importance. While they may be difficult to ascertain directly, comparison with better known diseases that are transmitted in a similar fashion might give some indication. Hepatitis B virus (HBV) shares many routes of transmission with HIV. We here propose a model, where the parallel seroconversion to HBV and HIV in a cohort of homosexual men is used to estimate the relative infectivities of the two diseases. For homosexual contacts HBV seems to be about 10 times as contagious as HIV.