SEATTLE, United States - Malaria and the AIDS virus appear to be fueling each-other's spread in sub-Saharan Africa in a kind of self-perpetuating loop, according to a new US study.

File picture shows Malawi AIDS orphans at a care centre on the outskirts of the capital Blantyre. Malaria and the AIDS virus appear to be fueling each-other's spread in sub-Saharan Africa in a kind of self-perpetuating loop, according to a new US study. [AFP]

Researchers at the Fred Hutchinson Cancer Research Center and the University of Washington said there was a substantial overlap between the two diseases in the region, where the human immunodeficiency virus ( HIV) which causes AIDS may be playing a role in boosting adult malaria-infection rates in some areas.

The findings, published in the December 8 issue of the journal Science, showed that because malaria helped to multiply by ten times the amount of HIV virus in an HIV-infected person's blood, the AIDS virus becomes more transmissible to a sex partner.

The research shows that conversely, HIV-infected persons are more susceptible to malaria infections due to their compromised immune systems, fuelling the spread of malaria in the region.

"While HIV/AIDS is predominantly spreading through sexual intercourse, this biological co-factor induced by malaria has contributed considerably to the spread of HIV by increasing HIV transmission probability per sexual act," said study co-author Laith Abu-Raddad of the Hutchinson Center and University of Washington.

"In turn, the weakening of the immune system by HIV infection has fueled a rise in adult malaria-infection rates and may have facilitated the expansion of malaria in Africa," said another co-author, James Kublin of the Hutchinson Center.

Using HIV and malaria co-infection data in Malawi, measured and collected by Kublin, the scientists for the first time were able to assess quantitatively the impact of malaria on HIV and vice versa.

They estimated that tens of thousands of HIV infections and millions of malaria cases were likely the result of this co-infection.

Kublin said that these findings suggest that other co-infections such as genital herpes or tuberculosis may have also contributed to the rapid expansion of HIV in Africa.

The study, also co-authored by Padmaja Patnaik, was funded by the Center for AIDS Research at the University of Washington.