Monday 1 December is the 20th anniversary of World Aids Day. Governments across the world have pledged to do more to tackle the disease that kills 6,000 people each day.
World Aids Day is dedicated to raising awareness of Aids and HIV
Here, UK International Development Secretary Douglas Alexander and Aids expert Dr Alvaro Bermejo from the International HIV/Aids Alliance answer some of your questions.
Q: What is the relative proportion of new infections among heterosexual and homosexual people? How has this changed from the first diagnoses in the late 70s and early 80s? The National Blood Service still forbids "men who have had sex with men" from donating, which seems based on the outdated opinion that HIV/Aids is a gay disease.
Carolyn, Colchester, England
Douglas Alexander: World Aids Day reminds us of the astonishing and horrifying speed at which Aids has moved around the world. A disease which just 25 years ago was commonly and wrongly seen as affecting European men, is now affecting a generation of African women. In the UK the number of new infections of HIV amongst gay men has risen by 1,000 in the last five years and it is right that they remain a target group for safe sex messages. However, the issue of complacency is relevant to all social groups in countries around the world.
Q: How long can a person with HIV live if they try to have a healthy life?
K R G, Barcelona, Spain
Dr Alvaro Bermejo: We know that if people are tested early enough, have access to life saving medication and treatment, good nutrition and support, it is possible for people to live with HIV for a very long time: 20-30 years, possibly more. And like all things in life, we should do things in moderation - they key is not to let HIV control you, but to control HIV.
Prevention is also vital. For those people who are positive and know their status having access to anti-retroviral therapy early really does change HIV from an early death sentence into a chronic health condition such as diabetes. But still 80% of HIV positive people do not know their status and people on average find out way to late to have the best benefit from treatment.
Q: We have heard time and again that behaviour change is vital to controlling HIV/Aids in Africa. Campaigns for abstinence, being faithful and using condoms don't seem to be working. What new approach have Aids experts come up with to control the spread of the disease?
Monica Mirigo Thiong'o, Nairobi, Kenya
Douglas Alexander: You're right, we do need to try new approaches. New infections are occurring in married couples at a high rate in many African countries - testing and counselling aimed specifically at couples could help, as could better access to both male and female condoms.
We're also funding research and development into a variety of medical ways to stop HIV infection. The UK is funding the world's largest clinical trial of microbicides, which are vaginal gels. We are also putting funding towards the research and development of Aids vaccines, and trials are looking at the use of anti-HIV drugs in people without HIV - to block infection.
Dr Alvaro Bermejo: There are, as this reader suggests, real problems with making HIV prevention work. Not just in Africa, but also globally. For every two people that get HIV treatment five become infected so it is vitally important that we get the correct packages of interventions delivered to all those who need them.
Increasingly we are seeing a 'feminisation' of the HIV epidemic - that is women and young girls being disproportionately at risk. This is particularly true in Africa where 59% of those who are positive are women. Underlying this are major inequities in access to education, unequal power dynamics and gender-based violence.
It is essential to use proven, evidenced-based preventative solutions - not those which are based upon ideologies. It is also important that those communities most affected are made an essential part of any response - be they young girls or married couples in Kenya, injecting drug users in Eastern Europe or gay men in UK or USA.
Q: How do studies aimed at collecting data about the spread of Aids deal with societies where the subject is taboo and people with the disease live in isolation?
RocketZ, Tripoli, Lebanon
Dr Alvaro Bermejo: There are different surveillance techniques (ways to collect data) which are used by countries to work out an estimate of HIV in different parts of their country. Establishing an effective surveillance system in all countries is vital. It allows you to plan your response. Surveillance data is collected in a way which means that it doesn't rely on people to be aware or disclose their status. This is how we know that there are very many more people living with HIV than know their status.
In many countries the type of information needed to properly plan an effective response is not routinely collected. Many countries do not, for example collect information on men who have sex with men (MSM). This is often in countries where it is illegal or taboo. But that doesn't get away from the fact that HIV is almost always disproportionately higher in MSM groups. For transgender populations the situation is even worse.
Q: What pressure, if any, will the UK government and worldwide health agencies put on the incoming Obama Administration to lift the ban on people with HIV entering the USA? This US policy directly reinforces stigma and ignorance about HIV/Aids.
Douglas Alexander: The US Congress has passed legislation this year to lift the travel ban. However, people who are HIV-positive are still required to obtain a visa before they travel because it's classed as a "communicable disease of public-health significance". We will be talking to the incoming US administration about a range of policy areas.
Q: Why is there not more publicity directed at the most at risk groups to never have sex without wearing a condom?
Andrew Sneddon, Bathgate, Scotland
Douglas Alexander: There already is a substantial amount of safe sex publicity targeting at risk groups living in the UK. It's just that it tends to be carried out by more community-based or specialist organisations, and not through mainstream media.
One-off media campaigns are not the best way to encourage consistent use of condoms in the long-term, though. Instead, people need to have regular contact with sexual health services, and need to receive safe sex education in a language they understand.
Preventing people becoming infected with HIV is our best hope of stopping the epidemic. The UK strategy emphasises the importance combining sexual and reproductive health and rights with HIV and Aids prevention. Since a campaign to get more people aged 15-24 using condoms was launched in Kenya in 2003, HIV rates have fallen from 13.5% to 9.4%. This is no doubt thanks in part to the campaign which raised awareness of the risk of catching HIV, and greater acceptance of the use of condoms.
Dr Alvaro Bermejo: The simple answer is that if all people at risk of infection used condoms consistently and correctly, it would reduce the number of future infections.
However, we should also remember that the majority of people infected with HIV globally do not know they are infected. Even in the UK, less than 50% of all people infected with HIV know their status. One of the global challenges is to ensure that people have access to HIV testing services and that we reduce the stigma and discrimination towards people living with HIV.
Q: How would you remove the perception that HIV and Aids is only an African problem?
Edith Lewis, Hayes, UK
Dr Alvaro Bermejo: It is right to acknowledge the disproportionate burden that sub-Saharan Africa carries when it comes to HIV and Aids. Two-thirds of current cases and three-quarters of the total deaths to date are found in that region.
HIV is not one global epidemic but is made up of many different types of epidemic. The real issue is for each individual country to be able to measure, understand and respond within their national context and need. This will require resources both from national governments but also donor agencies and global funding mechanisms such as the Global Fund, to which The Department for International Development and many other governments commit funding.
The important thing in this current economic crisis is to maintain the global commitment and response, to ensure that we build on the gains we have made.
Q: Much has recently been publicised concerning a HIV patient who had a bone marrow transplant for another illness. Now according to tests he appears to be HIV negative. Remarkable if true. What hope does this offer the world for a vaccine or cure?
Fred, March, UK
Dr Alvaro Bermejo: Let's deal with the science first. The patient in question was given a bone marrow transplant from a person who doesn't have one of the key receptors that HIV uses to get into cells. The HIV virus needs to get inside a particular type of cell - the CD4 cells - which are vitally important for controlling infection. If you block this you are essentially blocking HIV infection. This, however, is not a cure.
The tests that they use to detect the virus are the same tests we use to measure the effect HIV drugs are having. These tests are negative in a person who is on effective therapy. The difference in this case is that it is the body's own immune system which is controlling the virus. Unfortunately when a person with HIV stops their drugs the virus rapidly returns.
Bone marrow transplants are expensive. Although we can continue to wait for this to be translated into usable technology, for countries which have the highest burden of the epidemic we do have very effective prevention and treatment interventions which we can implement right now. The fact that we could virtually eliminate HIV transmission from mother to child by a set of relatively cheap interventions doesn't make headlines but half a million children are infected annually when this could be avoided.
The fact that 80% of the people in the world who have HIV do not know it and just increasing access to testing and information alone would impact on the epidemic is also true. But these things are less newsworthy.