Introduction: Accurate, comprehensive knowledge of an infectious pathogen's modes of transmission helps people to avoid infection. Growing evidence suggests that blood-borne HIV transmission is widespread in sub-Saharan Africa.

Methodology: I examined the association between knowledge of blood-borne HIV risk and prevalent HIV infection in Demographic and Health Survey data from 16 sub-Saharan African countries. I also searched three online databases for evidence of public education campaigns focused on blood-borne HIV risks in these countries.

Results: Knowledge was moderately to strongly inversely related to HIV prevalence at the national level (i.e., countries in which many respondents were aware of blood-borne risk had lower HIV prevalence than countries in which few respondents were aware of such risk). At the individual level, respondents who knew about blood-borne HIV risks were modestly less likely to be infected than those who did not show awareness of this risk, independent of demographic and sexual behavior variables. This relationship was stronger in southern Africa than in west, central, and east Africa. In parallel analyses, knowledge of condom use as a way to prevent HIV was positively associated with prevalent HIV infection at both the national and individual levels. West, central, and east African countries with low to moderate HIV prevalence had implemented public education campaigns that included a focus on blood-borne transmission risks. Such campaigns were absent from high prevalence countries in southern Africa.

Conclusion: These findings suggest that knowledge of blood-borne HIV risk protects against HIV infection and that public education campaigns are important for spreading that knowledge.