A Bristol University study of more than 43,000 people living with HIV has found that better treatments increase their life expectancy by 13 years.
A 20-year-old diagnosed today can expect to live for another 49 years.
The report claimed that because of advances in HIV drugs, it should be viewed in the same way as a chronic illness rather than a fatal disease.
However the report in The Lancet said that people with HIV have a shorter life expectancy than the rest of the population.
Professor Jonathan Sterne, a member of the Antiretroviral Therapy Cohort Collaboration at the University of Bristol, said:
“There has been a revolution in drug treatment for HIV since 1996.
“It has been transformed from a rapidly fatal disease to one with death rates more like diabetes. Suddenly we were able to stop the virus replicating and the immune system recovered.
“What we didn’t know was what the long-term effects would be.
“There were also worries that resistance would develop, as would side effects such as heart disease. Instead the drugs have got more effective, with few side effects.”
Despite improved life expectancy, many gay men choose not to have themselves tested for the virus. It is estimated that one in ten gay men in London has HIV.
People showing the symptoms of early-stage HIV infection are routinely being misdiagnosed by doctors, according to a report published earlier this week by the National AIDS Trust.
It found that in one Brighton study, almost half of those who sought medical advice for what eventually turned out to be HIV symptoms were not diagnosed correctly.
Symptoms of early-stage HIV include sore throat, fever and rash and will show within two to six weeks of infection in up to 90% of cases.
The report also found that 30 to 50% of new HIV infections are thought to be passed on by people in the early stage of infection, making the need to catch new cases early in order to prevent the spread of HIV a priority.
However, the study found that doctors and other healthcare professionals were commonly dismissing these symptoms as signs of common viral infections, with comments such as: “Probably glandular fever” or “Come back in two weeks if you’re not feeling better.”
HIV testing has seen great advances in recent years. The majority of cases can now be diagnosed from 12 days after infection.
However, the figures for HIV infection rates in the UK remain high. More than 80,000 people live with HIV.
A third of people with HIV are not diagnosed, and a third of those that are diagnosed are diagnosed late.