Skip to navigation | Skip to content

Malaria may fuel HIV spread

Malaria mosquito

Africa is suffering from a double blow: malaria and HIV. Now scientists say that one could exacerbate the other (Image: Science/CDC and Jim Gathany)

Malaria may be helping to spread HIV across Africa, the continent hardest hit by AIDS, scientists say.

The way the two diseases interact greatly expands the prevalence of both among people in sub-Saharan Africa, a team of scientists say today in the journal Science.

Malaria, a mosquito-borne disease caused by a parasite, greatly boosts viral load, the amount of HIV in the blood of infected people, they say.

This makes them more likely to infect a sexual partner with HIV.

"Higher viral load causes more HIV transmission, and malaria causes high HIV viral load," says lead study author Dr Laith Abu-Raddad of the Fred Hutchinson Cancer Research Center in Seattle and the University of Washington.

Abu-Raddad, an AIDS researcher, estimates that malaria has helped HIV infect hundreds of thousands and perhaps millions of people in sub-Saharan Africa.

At the same time, HIV fuels malaria's spread because HIV-infected people are more susceptible to malaria as a result of HIV ravaging the immune system, the body's natural defences, the researchers say.

AIDS and malaria are concentrated in sub-Saharan Africa. And Abu-Raddad says scientists were puzzled when they realised that the risky sexual behaviour by people in the region was not by itself sufficient to explain the swift spread of HIV, so other factors must be involved.

They focused their work on Kisumu, a Kenyan city by Lake Victoria where HIV and malaria are both common.

They say 5% of HIV infections can be blamed on the increased HIV viral load due to malaria, and 10% of adult malaria cases can be blamed on HIV.

Since 1980, 8500 more people became HIV positive, and there were 980,000 more episodes of malaria (a person can get it more than once) in a city whose adult population is 200,000, the study found.

Public health efforts

The findings have implications for public health efforts, Abu-Raddad says, showing the importance for authorities to tackle these diseases together.

Of the 39.5 million people worldwide infected with HIV, 24.7 million are in the poor countries of sub-Saharan Africa. About 2.1 million of the world's 2.9 million AIDS deaths in the past year were also in this region.

Malaria kills more than a million people annually, mostly young children in sub-Saharan Africa.

The researchers produced their results with a mathematical model using HIV and malaria infection data gathered in Malawi by Dr James Kublin of the Hutchinson Center.

This enabled them to quantify for the first time the synergy between malaria on HIV and its toll on people.

Scientists previously determined that a lack of male circumcision and the incidence of genital herpes also were facilitating the spread of HIV.

Abu-Raddad notes that circumcised men are much less likely to get HIV, and that genital herpes opens a door for HIV to infect a person.

Abu-Raddad says malaria now can be considered a third serious factor facilitating the spread of HIV.

The two diseases drive one another even though they have different modes of transmission - malaria by mosquito and HIV predominantly by sexual intercourse - Abu-Raddad notes.

He says once a person with HIV gets malaria, his or her viral load goes up and stays higher for six to eight weeks, making the person far more infectious to others.

Tags: health, biology