Improved medical treatment, both for HIV and the illnesses associated with it, has led to major changes in the pattern of HIV disease progression which people in the UK and similar countries can expect.

First of all, doctors have become very skilled at treating certain illnesses. For example, the AIDS-defining pneumonia, PCP, was often fatal in the very early days of the HIV epidemic. Now, doctors are able to treat it and people who have had it go on to live healthy lives for many years afterwards.

What’s more, doctors know how to prevent many infections from occurring in the first place. Once your immune system becomes damaged to such an extent that you are vulnerable to certain infections, it is possible to take medicines to prevent these developing. This is called prophylaxis.

However, the biggest improvement of all came in the mid-1990s, when effective treatment that targets HIV itself became available. This antiretroviral treatment has led to very substantial reductions in the numbers of people dying of HIV or becoming ill because of HIV in the UK and other countries. Use of antiretroviral drugs has been shown to prevent peoples' immune systems from becoming weakened by HIV. What’s more, antiretroviral therapy has also been shown to work for many people with advanced HIV disease, including people with AIDS. For many people in this situation, anti-HIV drugs have brought about a remarkable recovery in health.

It's also worth noting that there have been further significant improvements in HIV treatment since the mid-1990s with anti-HIV drugs becoming available that are more powerful, easier to take and less likely to cause side-effects than those used even five years ago. What's more, some promising new HIV drugs are in development.