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Filed under : Scitizen >> Health & Medicine >> AIDS >> HIV and Malaria: A Vicious Cycle Key words : hiv/aids,immunology,malaria,synergy,HIV and Malaria: A Vicious Cycle11 Jan, 2007 09:53 am | |
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Reduce text sizeHIV/AIDS and malaria continue to be two “elephants” of public health challenges. There are 40 million people infected with HIV with an annual mortality of three million. Moreover, there are over 500 million clinical malaria infections every year with more than a million deaths. Both infections are concentrated and overlapping in sub-Saharan Africa. The sheer scale of the two diseases guarantees that any clash between these two elephants is likely to yield to considerable public health consequences.
Two parallel threads of scientific development have fueled a speculation of synergy between the two diseases. The first was a characterization of the relationship between the amount of HIV virus in the blood and the HIV transmission probability per sex act. It was found that with each factor of ten increase in the concentration of the virus in the blood, the transmission probability increases by a factor of two and half. The second thread of development was a characterization of the biological interaction between HIV and malaria. It was found that HIV infected persons are twice as likely to acquire malaria infection by virtue of their weakened immune system. Of more consequence, it was discovered that when an HIV infected person acquires malaria, the number of HIV viruses in his or her blood increases by a factor of seven for six to eight weeks. The underlying mechanism of this increase is that upon malaria infection, the human body produces billions of immune cells to overcome malaria devastation of red blood cells, but some of these immune cells are precisely the target cells that the HIV virus attacks and use as “weapon factories” to produce more viruses.
These scientific findings suggest a vicious cycle of interaction between the two diseases. HIV infection facilitates malaria acquisition. In turn, the immune reaction against malaria makes dually infected persons twice as infectious for HIV. Therefore, HIV fuels malaria and malaria fuels HIV. Thus, we asked the question: how many excess HIV and malaria infections does this vicious cycle produce? To address this question we went to Kisumu, Kenya, a district of about half a million people and synthesized the available biological, behavioral, and demographic data in this district into a mathematical model to estimate the impact of HIV and malaria on one another.
We found that 5% of all HIV infections in Kisumu are attributed to the higher HIV infectiousness of malaria-infected HIV patients. This translated into 8,500 HIV infections since 1980. Moreover, we found that 10% of adult malaria episodes are attributed to the higher susceptibility of HIV persons to malaria. This translated into almost one million excess malaria infections since 1980. Lastly, we found that HIV may have played a role in the geographic expansion of malaria in Africa.
These findings suggest that HIV co-infections, such as with malaria but also with genital herpes and tuberculosis among other diseases, may have played a substantial role in fueling HIV spread in sub-Saharan Africa. This outcome offers a partial solution to the “African puzzle” that HIV has spread rapidly in sub-Saharan Africa though the level of sexual promiscuity in this region does not seem to sustain such extensive infectious spread. HIV is predominantly transmitted through sexual intercourse, but biological cofactors enhance HIV spread by increasing HIV transmission probability per sexual act.
These findings highlight how the HIV virus, by holding the immune system hostage, has opened many gates for pathological interactions with other diseases. The failure of the global public health system in dealing with the challenge of HIV/AIDS has contributed directly to the failures of the efforts of tackling other public health challenges such as malaria and tuberculosis. As long as HIV/AIDS continues to spread, it will magnify the difficulties we face with other infectious diseases and may contribute to the emergence of more lethal or drug-resistant strains of such infections.
The synergy between HIV and other diseases such as malaria provides us with more opportunities to combat HIV/AIDS by treating its co-infections with these other diseases. This outcome highlights the fact that global public health challenges require comprehensive and multi-pronged approaches to dealing with them. Current efforts that focus on a single infection at a time may be losing substantial rewards of dealing synergistically and concurrently with multiple infectious diseases.
Abu-Raddad, L. and Kublin, J.G. Dual Infection with HIV and Malaria Fuels the Spread of Both Diseases in Sub-Saharan Africa. Science. 8 December 2006: Vol. 314. no. 5805, pp. 1603 - 1606. DOI: 10.1126/science.1132338.
Dr. Abu-Raddad is with the Statistical Center for HIV/AIDS Research & Prevention.
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| [1] | Comment by Dr Laith Abu-Raddad - 1 Mar, 2007 07:23 pm Very interesting findings!! I do have a question: Does the malaria mosquito transmit HIV? Regards, M. Elsafi melsafi_dds@yahoo.com [Response] No! There is not enough virus count in a mosquito bite to establish an HIV infection within a human host. Regards, Laith | ||
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