An expert in emerging diseases, Dr Robert Webster of St Jude Children's Research Hospital in Memphis, today speculated that HIV may allow the avian influenza (H5N1) virus to mutate to a strain that could be passed more easily between humans.
Dr Webster, who was speaking at a conference in New York, organised by the Council on Foreign Relations, said that this may occur when H5N1 reaches East Africa, where HIV prevalence is high, and where social conditions and farming practices are similar to those in Asia, where the so-called 'bird flu' virus first emerged.
He told BBC online that once H5N1 infected HIV-positive people with compromised immune systems, this could allow avian influenza enough time inside the human body to mutate into a more virulent form.
His theory is based on his previous experience with immune-compromised cancer patients, who were slower at clearing non-avian influenza, shedding viral particles for weeks. "We're all very worried by the prospect," he told the BBC.
Although H5N1 has not yet reached any country in East Africa, the Food and Agriculture Organisation of the United Nations expect East Africa to be the final destination for many birds currently migrating from infected areas.
Earlier this month, in written testimony before a United States Senate hearing of The Committee on Foreign Relations, Pulitzer Prize-winning health journalist Laurie Garrett explained that there are currently two theories regarding how HIV and the 'bird flu' virus would interact.
It is believed that the H5N1 virus kills by over-stimulating cytokines in the immune system, many of which are suppressed by HIV infection. This could mean that many people with HIV-related immune dysfunction will survive the infection. However, Garrett suggests, this may lead to "permissive environments for H5N1, allowing the flu virus to thrive, mutate and adapt to human beings. In such a scenario, the HIV+ person is, in a sense, an ambulatory Petri dish, incubating, and possibly spreading, new forms of the virus."
The other theory suggests completely the opposite: that HIV-positive people with suppressed immune systems would be more vulnerable to 'bird flu' and be more likely to die. "In that situation vast populations of HIV+ people could be obliterated by the pandemic flu," wrote Garrett.
Garrett points out that the public health infrastructures and surveillance systems in sub-Saharan Africa are not ready for either scenario, and that monitoring "the emergence of clusters of people with high fevers and nausea might be impossible against a background of malaria, tuberculosis and HIV."