DR MIKE YOULE:
Oh, there's this great belief that it doesn't really matter. You get HIV, then somebody treats you and you'll be fine forever. That's not the case.

DEENAN PILLAY:
We're seeing an increasing rate of transmission of those resistant viruses to newly infected individuals.

RON ANDERSON:
We're beyond that silent phase and on the beginning of the rapid-rise phase.

SUSAN WATTS:
Doctors are worried that complacency has replaced the fear of AIDS that swept Britain in the 1980s. Today's young gay men haven't seen their friends die in the way others did ten years ago, because of the success of HIV drugs.

UNKNOWN MAN:
There's a feeling that it's not a death sentence now.

SECOND UNKNOWN MAN:
It's more of a chronic illness these days than a terminal one, because of the drug treatment. People are more relaxed about it.

THIRD UNKNOWN MAN:
Older gay men are probably know more people who are openly HIV and have probably experienced more people die from HIV than younger gay men who are still quite naïve.

SUSAN WATTS:
New research is shattering the notion that in the western world at least, you can live with HIV. The triple therapy drug cocktail that seemed to keep AIDS at bay has started to stop working. Just three years ago it was rare to see resistance to drugs in newly- infected people. But Newsnight has learned that now a quarter of all new cases are resistant to drugs. The problem with HIV is that every time the virus replicates there are subtle changes in its genetic code. Each individual has so many HIV viruses inside them that every day, every genetic change that CAN happen WILL happen. The drugs will kill off some of these viruses, but those that by chance acquire changes that help them to resist that drug, survive and replicate. So, over time resistant viruses thrive, causing the same problems as antibiotic resistance. When the drugs don't work, doctors send samples from the patient to this lab in Birmingham to find out if resistance is the problem.

DEENAN PILLAY:
PHLS ANTI-VIRAL UNIT, BIRMINGHAM
Blood samples come in to our lab from all over the country from patients infected with HIV who are receiving therapy but who are failing on that therapy. This emanates from one of those samples from a patient who is receiving combination therapy but that therapy is not working.

SUSAN WATTS:
Deenan Pillay examines the individual viruses these patients carry to see if he can find clues in their genetic codes.

DEENAN PILLAY:
The question we want to ask is what mutations they have in the genes of the virus. We then treat those samples with fluorescent dyes, which allow this machine here, which incorporates a laser reader, to read the genetic code from those genes. In other words, the genes from the virus from that patient who donated the sample is now being fully sequenced.

WATTS:
Scientists know there are at least 250 points in the genetic code of HIV where changes can make it resistant to drugs. So the team homes in on those and decodes them. This gives them a genetic "fingerprint" of the virus inside the individual.

DEENAN PILLAY:
We then submit this large amount of genetic data from that one particular patient to a database held at Stamford University in San Francisco and this helps us to then interpret this information with regard to drug resistance.

WATTS:
Within seconds, the Stamford system sends back a detailed breakdown of suspect mutations.

DEENAN PILLAY:
We then use the data from this database to produce a report which goes to the clinician who cares for the patient from whom the sample has come. We give an interpretation as to how susceptible the virus from this patient will be to the array of drugs available.

WATTS:
There are three groups of drugs used. The problem is that if the virus evolves to become resistant to one drug in a group - such as AZT - it soon becomes resistant to all of them, so wiping out the benefits of triple therapy. Most worrying of all , the evidence, it suggests these resistant strains are now being passed on. Brand new cases are showing up at clinics that are already drug resistant, and in accelerating numbers.

DEENAN PILLAY:
We're seeing that an increasing proportion of those newly infected individuals are being infected with resistant virus, up to something like 20%.

WATTS:
And even in people who aren't originally infected with resistant strains, resistance soon develops.

PILLAY:
Something like 40% of those individuals who are on treatment and in whom the virus rebounds have resistance to at least one of the three currently available classes of drugs. More worryingly, something like 10 to 15% of those individuals in whom rebound of virus while they're taking the therapy occurs, have resistance to drugs within all the three currently available classes.

WATTS:
Could a new class of drugs be the answer?

DR MIKE YOULE:
ROYAL FREE HOSPITAL, LONDON
This is the new T20. There's 28 phials in there, which is 14 days. A patient injects one twice a day.

WATTS:
This month, Dr Mike Youle has started the UK's first clinical trials of T20 - the first of a new type of drug called fusion inhibitors which stop the virus sticking to the patients' cells.

DR MIKE YOULE
It's easier for the public and for public health deliberators to think that the HIV epidemic is over, and there are no problems and that all the treatments we have are effective and will last for ever, and I think that we who look after patients constantly and those who are developing drugs realise that is not the case. We're now developing some new agents called fusion inhibitors. These basically stop HIV getting into the cell and that's a good thing. This is new and it hasn't been done before.

WATTS:
But back at the resistance lab, evidence from America shows that before T20 is in commercial production, its effectiveness could already be compromised.

PILLAY:
Resistance has been documented in the test tube, where HIV virus can be grown in the presence of this particular drug, this particular fusion inhibitor. Furthermore, we now know from very early clinical use of this drug that resistant virus to this drug can occur.

PUBLIC HEALTH WARNING:
"There is now a danger that has become a threat to us all. It is a deadly disease and there is no known cure¿"

WATTS:
Some experts are warning that drug resistance means the Government will have to hammer home the safe sex message as strongly as it did when Norman Fowler launched the AIDS campaign in the 1980s. The epidemiologist whose alarming estimates of the scale of the AIDS problem triggered that campaign is now advising the Government on the risks posed by resistant viruses.

ROY ANDERSON:
We can't rely on the drugs alone because of the high evolution potential of this virus.

WATTS:
Roy Anderson believes that unless patients can be convinced to take all their pills at the right time for the rest of their lives, resistance will increase very fast.

ROY ANDERSON:
IMPERIAL COLLEGE, LONDON
It's what you call an S-shaped curve, so you have, post the evolution of the resistant virus, a very long silent period, then suddenly it starts to change and grow exponentially.

WATTS:
From 1984 to 1995, AIDS-related deaths rose rapidly to nearly 17,000 cases a year. Then the new triple therapy drugs came in and the death rate plummeted to over 300 last year. But it's unlikely to stay that low. New cases of HIV have been running at between two and 3,000 per year. When the drugs first came in they encountered no resistance from the virus. But now a quarter of new patients are resistant to the drugs which they hope will save their lives.