HIV, Malaria Fuel Each Other's Spread, Study Says

Scott Norris
for National Geographic News

December 7, 2006

A deadly synergy between HIV and malaria appears to be fueling the spread of both diseases in Africa, a new study suggests.

The report, in tomorrow's edition of the journal Science, is the first to assess how Africa's increased rates of infection are in part caused by an interaction between the two diseases.

HIV makes people more vulnerable to malaria by weakening their immune systems, the researchers say, and contracting malaria may worsen a patient's pre-existing HIV infection, possibly making it more communicable.

Scientists researched the extent of this interaction by studying disease patterns in 200,000 adults in Kenya (see Kenya map).

The scientists found that within this group, about 5 percent of all HIV infections could be attributed to malaria, and 10 percent of all adult malaria episodes could be attributed to HIV.

Dual infection has caused an estimated 8,500 new HIV cases and nearly a million malaria episodes since 1980, the researchers say.

The study suggests that malaria may be a contributing factor to the HIV/AIDS epidemic in sub-Saharan Africa.

"These are two elephants affecting public health in Africa," said the study's lead author Leith Abu-Raddad of the Fred Hutchinson Cancer Research Center in Seattle.

"Any interaction between them is consequential.

"We can't yet say how many cases of HIV malaria has caused over all of Africa," Abu-Raddad said.

AIDS, the disease caused by HIV, and malaria are two of biggest causes of death in sub-Saharan Africa, killing an estimated four million people a year combined.

Disease Dynamics

Scientists have known for some time that the immune system suppression caused by HIV can increase both the risk and severity of malaria infection.

But the idea that malaria might fuel the transmission of HIV is more recent.

Malaria sufferers often experience repeated, nonlethal outbreaks of the disease's flulike symptoms, with episodes varying in severity.

Studies have shown that in people infected with both diseases, the amount of HIV virus in their bodies goes up significantly during these malaria episodes.

Other research has demonstrated that as the amount of HIV virus goes up, so does the likelihood of HIV transmission through sexual intercourse.

These two factors together can cause HIV to spread more rapidly in populations where malaria is present.

"Malaria cannot be the only reason why HIV has so predominantly affected sub-Saharan Africa," said James Whitworth, a scientist not involved in the study, of the medical research nonprofit Wellcome Trust in London.

"But it is certainly plausible that is has been an important cofactor in driving transmission."

The discovery of a significant HIV-malaria interaction suggests the need for a coordinated approach in fighting both diseases, scientists say.

"It highlights the need to integrate health programs," said Jonathan Mermin, a physician with the U.S. Centers for Disease Control and Prevention working in Kenya.

"People with HIV should be provided with insecticide-treated bed nets and [anti-malaria medications]," Mermin said.

"Efforts to prevent and eliminate malaria should be increased, alongside efforts to prevent and treat HIV infection."

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