AIDS - after 21 years
with Dr Walter Chin
December 8, 2002
The first intimation of the beginning of the AIDS epidemic was the publication in the June 5, 1981, issue of Morbidity and Mortality Weekly Report, the bulletin of the Centers for Disease Control (CDC), of a report on five cases of an unusual form of pneumonia in young homosexual men. The pneumonia was caused by pneumocystis carinii, a rare form of infection. Some of the patients also had oral fungal infections (candidiasis). The report highlighted the fact that the patients were all homosexuals, suggesting that there was "an association between some aspect of a homosexual lifestyle or disease acquired through sexual contact and pneumocystis pneumonia in this population." The report concluded that the cases suggested "the possibility of a cellular-immune dysfunction related to a common exposure that predisposes individuals to opportunistic infections such as pneumocystosis and candidiasis."
As we are now into the 21st century, we can reflect on the fact that the 20th century has seen two unexpected health epidemics with momentous impact. The first was the influenza pandemic of 1918, responsible for the deaths of approximately 25 million people worldwide. The second is, of course, the acquired immunodeficiency syndrome (AIDS).
The significance of the June 5 report was probably not realised at that time, and no one thought that it might herald the start of a world-wide health catastrophe. Since then the impact of AIDS has become clearer, if still not fully comprehended. Since that report, more than 60 million people have been infected with the virus, and AIDS has claimed more than 25 million lives. At present, 42 million adults and children, mostly in sub-Saharan Africa, are living with human immunodeficiency virus infection or AIDS.
The disease has orphaned millions of children. The magnitude of the epidemic is huge, and is far more extensive than was thought likely in the early 1990s. HIV infection is spreading rapidly in many areas, including China (about a million Chinese are infected with the virus), Eastern Europe, and Central Asia. Every day, more than 10,000 people around the world become infected with HIV. It is estimated that the AIDS epidemic will cause the deaths of 55 million people by 2010, exceeding the 25 million caused by the Black Death (bubonic plague) in the fourteenth century. Not since the Black Death has there been an infectious disease outbreak as devastating as HIV.
The demographic characteristics of those affected by the epidemic have changed considerably since the first cases were reported. Unlike the early days of the epidemic, when the affected population consisted overwhelmingly of homosexual men, today new cases of HIV infection result predominantly from injection-drug use, heterosexual contact, and mother to infant transmission. As the number of new cases has decreased among homosexual men, the number of new infections, particularly among women, has increased sharply.
In the developed countries, the numbers of new AIDS diagnoses and deaths have fallen substantially. This trend is due to several factors. These include improved prophylaxis against opportunistic infections and improved treatment. The most influential factor has been the increased use of potent anti-HIV drugs, generally administered in combinations of three or more agents. Such combinations are known as highly active anti-retroviral therapy or HAART. The development of therapies for HIV infection has been quite successful, and there are many drugs now licensed for use in treatment. These drugs have had tremendous effects in reversing the extent of illness in many patients with advanced disease, as well as in preventing the progression of disease in those who are relatively healthy. They have also markedly reduced the risk of HIV transmission from mother to baby.
The use of anti-retroviral drugs in pregnant women with HIV infection and their infants is a successful prevention strategy. It is now known that a short and affordable regimen of therapy administered to the mother around the time of delivery could prevent HIV infection in hundreds of thousands of babies every year.
Despite the enormous benefits of HAART therapy, many HIV-infected people have not responded satisfactorily to the drugs, or cannot tolerate the toxic effects. Some have difficulty in complying with the treatment which involves large numbers of pills and complicated dosing-schedules. Even in patients who are successfully treated, the virus persists in areas where the drugs cannot reach it or exists in a form where the drugs have no effect. In addition, the emergence of strains of HIV that are resistant to currently available drugs is widespread and growing.
Although there is improvement in the immune system function in most patients who receive combination anti-retroviral therapy, complete normalisation of the immune system and complete eradication of the virus from the body is unlikely with the present therapies. The development of a new generation of therapies therefore remains a major priority.
In the developing countries, the cost of anti-HIV therapies is beyond the reach of most patients. In the developed nations, there were 25,000 deaths from AIDS in 2001, and there were about 500,000 people using anti-retroviral drugs against HIV infection. In sub-Saharan Africa, however, there were 2.2 million deaths, and only about 25,000 people receiving anti-retroviral treatment. This emphasises the need for lower-cost drugs and for effective prevention of HIV.
Even if the price of drugs allowed greater access for HIV infected persons, treatment is not the solution to the global HIV problem. Unlike some infections such as malaria and tuberculosis, HIV infection in adults is entirely preventable by behaviour modification. Two interventions have been shown to effectively limit the spread of HIV: sex education and the use of condoms.
Preventive programmes based on public education, counselling, and the distribution of condoms and clean needles have markedly reduced the spread of HIV in recent years. However, it is now realised that such efforts alone cannot win the war against AIDS.
One of the solutions to the HIV pandemic is the development of a safe and effective vaccine against the infection. There seems little doubt that a safe and effective vaccine against HIV can be developed. Studies and intensive research suggest that commercial production of a preventive vaccine is a feasible goal, but this is unlikely to be achieved before 7-10 years.
On the plus side, the AIDS epidemic ushered in a scientific research effort without parallel and has spurred work into the underlying mechanisms of disease. It has improved our understanding of the complexity of the immune system, which has implications for numerous other diseases. People with AIDS, for example, whose immune systems are severely compromised, are more susceptible to cancer, indicating that the immune response plays a key role in the development of cancer. Research has also showed that there is an association between viruses and cancer - suggesting that cancers caused by viruses can be treated or even prevented by use of a vaccine. It will be some time before there is a real sense of all the discoveries sparked by HIV research.
A new global health fund - a key project of the United Nations Secretary General Kofi Annan - has been set up to provide more resources for the control of HIV infection and AIDS, tuberculosis, and malaria.
Estimates suggest that about $10 billion annually is required to upgrade existing programmes to tackle the three diseases. So far only $1.9 billion has been pledged for the fund, of which $700-800 million will be disbursed this year and the rest in 2003. The fund is already overwhelmed with applications from developing countries, and it remains to be seen whether the developed countries and global corporations will take up the challenge to reach the estimated sums required.