In many parts of the world with high HIV infection rates, malaria is also endemic. For some time, scientists have suspected that each of the two diseases contributes to the other's spread. Now researchers from the University of Washington have added some statistical weight to this theory. Doctors Laith Abu-Raddad and James Kublin studied several hundred people with HIV who live in the Kenyan city of Kisumu. They found that when people with HIV get malaria, the count of human immunodeficiency viruses in their bloodstream increases seven-fold.

One African child dies from malaria every 30 seconds

"Now we know that if a person has more viruses within his body, he's more likely to transmit these viruses to other people," says Abu-Raddad. "Malaria can make HIV spread more because it allows people to be more infectious."

The researchers also found, not surprisingly, that because HIV weakens or destroys the immune system, people with HIV were more susceptible to contracting malaria, as well as many other infectious diseases.

Using these findings, Abu-Raddad was able to calculate that in terms of infections from both diseases in Kisumu over the past 25 years, the HIV/malaria interaction has taken a significant toll on public health. "We estimated that 5 percent of all HIV infections are actually due to malaria. So over 25 years, this translates to 8,500 HIV cases who get their HIV because of malaria." In addition, he says, HIV infections in Kisumu alone resulted in almost a million additional malaria cases over 25 years.

Abu-Raddad compares the confluence of the two diseases to a clash of elephants. "There are 40 million people infected with HIV AIDS in the world and there actually 500 million malaria cases as well," he says. "These two elephants could clash between each other and in fact they do in Africa because the areas that have HIV also have malaria."

The report, which appears in this week's issue of the journal Science, recommends that people who are receiving anti-retroviral medications to fight their HIV should also be treated phophylactically against malaria. Abu Raddad says his colleague James Kublin is returning to Africa to gather more

data so they can refine their disease model and better understand how HIV acts in the body.