In a series of articles, Dr David Gisselquist, Mr John Potterat and colleagues argue that the spread of HIV infections in Africa is closely linked to medical care. In their unique study of existing data from across the continent they estimate that only about a third of HIV infections are sexually transmitted. Their evidence suggests that "health care exposures caused more HIV than sexual transmission", with contaminated medical injections being the biggest risk.

• HIV and STDs: According to the authors' data, African HIV did not follow the pattern of sexually transmitted disease (STD). In Zimbabwe in the 1990s HIV increased by 12% a year, while overall STDs declined by 25% and condom use actually increased among high-risk groups.
  
   
• Infection rate: HIV spread very fast in many countries in Africa. For the increase to have been all via heterosexual sex, the study claims, it would have to be as easy to get HIV from sex as from a blood transfusion. In fact, HIV is much more difficult than most STDs to transmit via penile-vaginal sex.
  
   
• Risky sex? Several general behaviour surveys suggest that sexual activity in Africa is not much different from that in North America and Europe. In fact, places with the highest level of risky sexual behaviour, such as Yaounde in Cameroon, have low and stable rates of HIV infection. "Information…from the general population shows most HIV in sexually less active adults" .

• Children and injections: Many studies report young children infected with HIV with mothers who are not infected. One study in Kinshasa kept track of the injections given to infants under two. In one study, nearly 40% of HIV+ infants had mothers who tested negative. These children averaged 44 injections in their lifetimes compared with only 23 for uninfected children.
  
   
• Good access to medical care: Countries like Zimbabwe, with the best access to medical care, have the highest rates of HIV transmission. "High rates [of HIV] in South Africa have paralleled aggressive efforts to deliver health care to rural populations".
  
   
• Riskier to be rich: Most STDs are associated with being poor and uneducated. HIV in Africa is associated with urban living, having a good education, and having a higher income. In one hospital in 1984, the rate of HIV in the senior administrators was 9.2%, compared with the average employee rate of 6.4%.

They conclude: "a growing body of evidence points to unsafe injections and other medical exposures to contaminated blood" as an explanation for the majority of the spread of the epidemic. "This finding has major ramifications for current and future HIV control programmes in Africa" .