It comes as the number of those living with the virus in the UK reaches 100,000, and the reason the virus is spreading faster than it ever has before is because of the the amount of people, estimated at around 20,000, who are unaware of their infections.
The number of people diagnosed with HIV in the UK has reached a record high, passing 100,000 for the first time, the Terrence Higgins Trust said.
Though the number is "worryingly high" according to Paul Ward from the Terrence Higgins Trust, it is better to have people diagnosed and getting the world class treatment available in the UK, than continuing unaware of their infection.
There is a stark warning on World Aids Day that 25,000 people in the UK are infected with the HIV virus, without knowing about it. It raises concerns that they are not getting potentially lifesaving treatment early enough and could be passing it on and infecting others.
Experts say the number of cases is actually falling in hotspots such as Africa and America, leading David Cameron to call for better education about the condition and more routine testing. Watch this report from Martha Fairlie.
Paul Ward of the Terrence Higgins Trust has said that there is still more to be done in the fight against HIV and Aids.
Speaking before a service to mark World Aids Day, Mr Ward told ITV News; "the real challenge we've got is the 25% of those people who have not been diagnosed. What we would like to see is... much more work to expand the access and make it much easier to take an HIV test."