Infection with the threadlike roundworm Wuchereria bancrofti more than doubles the risk of HIV in adolescents and young adults in Tanzania. Publishing their findings in The Lancet, researchers conducted a population-based cohort study in which between 2006 and 2011, they sampled about 10 percent of households (4,283) in nine sites in southwest Tanzania, tested individuals for HIV and tested a subgroup for indicators of infection with adult W. bancrofti worms.

Out of about 18,000 participants, a total of 2,699 people from the Kyela district of Tanzania participated in at least one round of the study. Out of this group, 1,055 people were tested for roundworm infection. During the study period, 32 people contracted HIV. Those who tested positive for roundworm had an overall HIV infection rate of 1.91 percent per year, compared with 0.8 percent per year among those who tested negative for the worm.

After controlling for age and sex, the researchers found that overall, testing positive for roundworm was associated with a 2.17-fold increased HIV infection rate compared with testing negative for roundworm. Among those 14 to 25 years old, roundworm infection was associated with a 3.2-fold increased HIV rate, while there was a 2.4-fold increased risk of HIV among 25- to 45-year-olds and a 1.2-fold increased risk of HIV among those older than 45.

Infection with roundworm remained an independent risk factor for HIV infection when the researchers controlled for other risk factors such as sexual behavior and socioeconomic factors.

To read a press release about the study, click here.

To read the study abstract, click here.