An aggressive new strain of HIV has been discovered in West Africa which leads to Aids at a worryingly fast rate.
Researchers from the University of Lund in Sweden found that the new HIV strain leads to Aids within around five years - the shortest reported period among HIV-1 types and significantly faster than currently prevalent forms of the disease.
The research comes ahead of the 25th annual World Aids Day, which will take place on 1 December. Millions of people from around the world will unite against the disease and remember the estimated 25 million people who have died from the virus between 1981 and 2007.
There are over 60 different strains of HIV-1, the most common and pathogenic strain of the virus.
Geographic regions are normally dominated by one or two strains of the virus. However, if a person is infected with two different strains, they can join together and lead to a recombined form.
The new strain has been called A3/02 and is a cross between the two most common strains found in Guinea-Bissau in West Africa, 02AG and A3.
Disease progression was measured from the time HIV was detected to Aids and Aids-related deaths. They found that people with A3/02 had a 300% higher risk of Aids and Aids-related death compared with people carrying the A3 type of the disease.
HIV epidemic changes
"Individuals infected with A3/02 have among the fastest progression rates to Aids reported to date. Determining the HIV-1 subtype of infected individuals could be important in the management of HIV-1 infections," the study said.
Angelica Palm, of Lund University, said: "Recombinants seem to be more vigorous and more aggressive than the strains from which they developed."
So far the new strain has only been found in West Africa, but previous research has shown the spread of recombinants is increasing. Studies have also shown that countries with high levels of immigration are seeing increasingly mixed and complex HIV strains.
Experts say that, for this reason, it is very important to be wary of HIV recombinants.
Researcher Patrik Medstrand said: "HIV is an extremely dynamic and variable virus. New subtypes and recombinant forms of HIV-1 have been introduced to our part of the world, and it is highly likely that there are a large number of circulating recombinants of which we know little or nothing.
"We therefore need to be aware of how the HIV-1 epidemic changes over time."