A new strain of HIV has been found in Cuba, which progresses to AIDS twice as fast as the average strain of the virus.

The strain, which is a mix of three subtypes of HIV, can progress to AIDS within 3 years without treatment- twice as fast as the 6 to 10 years that the average strain takes to progress.

According to The Seattle Times, Anne-Mieke Vandamme, a professor at the University of Leuven, and a team of researchers travelled to Cuba after an increasing number of HIV infections that rapidly spread to AIDS were reported.

The researchers studied 73 patients who had tested negative for HIV within three years, but who recently contracted the virus. All of the patients at the Tropical Medicine Pedro Kouri in Havana infected with the strain of HIV, known as recombinant, progressed to AIDS within three years and none of them received treatment before progressing.

More than 60 strains of HIV type 1 exist in the world because of mutations. The rapid nature of this new Cuban strain makes it difficult to treat.

Researchers also found that people having unprotected sex with multiple partners increased their risk of contracting multiple strains of HIV that could mutate or recombine into a new strain.

The research has been criticised, however, as the sample size of 95 patients is too small out of the some 15,000 Cubans living with HIV.

In the UK, HIV diagnoses have fallen from 6,333 in 2010 to 6,000 in 2013, and the proportion of late diagnoses of HIV continues to decline- down to 42% in 2013 from 50% in 2010.