It is believed that ten million intravenous drug users are infected with ; China (1.6 million), the United States (1.5 million), and Russia (1.3 million) have the highest absolute totals.
V 20 % primerov vzroka za prenos ni mogoče ugotoviti; za številne med njimi pa ocenjujejo, da je vzrok intravensko jemanje mamil.