Two new studies suggest a health care link as HIV evolved from a chimp's infection -- possibly transmitted to bush-meat hunters by bite or blood -- to its earliest human dissemination and global spread.
Scientists have theorized that the HIV pandemic was sparked after colonial-era urbanization fueled changes in sexual behavior. The new studies -- by Jacques Pepin, of the Université de Sherbrooke in Montreal, and colleagues -- propose that sexual transmission might have been secondary to initial blood-borne dissemination of HIV from a few isolated cases. Syringe reuse during early 20th century mass-vaccination campaigns against endemic diseases in Equatorial Africa may have inadvertently spread HIV and jumpstarted the pandemic, they suggest.
"What happened is that for a long time, the needles and syringes used to administer the intravenous drugs were not single-use," Pepin says. "There were a lot of patients and not a lot of needles, so the sterilization of needles was not very efficient. If HIV was present in one of these patients 50 years ago, we can assume that they probably transmitted HIV."
Because villagers from that era with HIV would be long dead, Pepin used less-lethal viruses, hepatitis C virus and human T cell lymphotropic virus 1, to track the colonial-era vaccination campaigns among villagers.
In the Central African Republic, the only risk factor for HCV genotype 4 infection was having received injections for sleeping sickness before 1951, the cross-sectional study found. HTLV-1 infection was associated with having two or more such injections and with transfusions. The number of people age 65-plus who had been treated for sleeping sickness was six times lower than would be expected from historical data -- possibly because many patients were lost to AIDS, Pepin explains.
In Cameroon, 56% of participants were HCV-positive. Independent risk factors included IV treatment against malaria, older age, attendance at an ethnic school (women only), and traditional male circumcision.
The studies, "Risk Factors for Hepatitis C Virus Transmission in Colonial Cameroon" and "Iatrogenic Transmission of Human T Cell Lymphotropic Virus Type 1 and Hepatitis C Through Parenteral Treatment and Chemoprophylaxis of Sleeping Sickness in Colonial Equatorial Africa," were published in Clinical Infectious Diseases.