The Shadow Plague
The XIVth International Conference on AIDS in Barcelona last month put the global HIV epidemic back in the spotlight--justifiably so. The UN estimates that the number of HIV/AIDS sufferers, currently at 40 million, will rise sharply in coming years, and 25 million children under age 15 are expected to lose one or both parents to the disease by 2010. But the continuing spread of HIV is closely linked with the growing resurgence of a much older killer.
Tuberculosis (TB) is an air-borne disease, transmitted the same way as common flu, by coughing or sneezing, although it is much less infectious. But, unlike flu, TB bacilli can survive in the lungs for years, surrounded by a "protective" wall built by the human immune system. These latent bacteria can be activated when other factors reduce the body's immunity to infection. This is why, over the centuries, poor living conditions, malnutrition, and diabetes always accompanied TB outbreaks.
During the past twenty years, the spread of HIV has dwarfed these historical accomplices in fuelling TB infection to an alarming rate worldwide: 8.7 million new cases per year and 2 million deaths. The vast majority of TB deaths occur in the developing world--largely induced by HIV. Indeed, more than 25% of preventable deaths in developing countries are due to TB. Because the young and economically productive age groups are the hardest hit, the disease's overall impact is even more destructive--condemning poor countries to generations of grinding despair.
Unlike HIV, there is a vaccine against TB (although not very effective), and several drugs that can reliably cure the disease after it emerges. The key element in any comprehensive eradication effort is rapid diagnosis and treatment of infectious cases. Diagnosis is cheap, simple, and quick: for a few US cents, microscopic examination of a sputum smear can reveal the bacilli in less than 1 hour. Treatment consists of a cocktail of antibiotics (four drugs for two months, followed by two drugs for four months) that, if correctly applied, can cure over 95% of TB cases for about $30 per case.
The problem is that treatment is too often abandoned at the first signs of clinical improvement - usually after 2-3 months. Members of high-risk groups, such as immigrants, the homeless, commercial sex workers, and the poor, are forced to move or search for work. In such cases, newly selected drug-resistant bacilli may appear, leaving only second-line drugs that are more toxic and expensive. The more these second-line drugs are used, the faster drug-resistant strains emerge and spread - a huge problem in former Soviet countries, where up to 10% of newly diagnosed cases are multi-drug resistant.
The World Health Organization (WHO) recommends a broader strategy - called DOTS - that calls for government commitment to TB control, including adequate diagnostic testing, continuous drug supply, and a proper system for recording, reporting, and assessing results. Moreover, the DOTS strategy requires that health care professionals supervise the standard treatment regimens to ensure that TB patients remain on the antibiotic cocktail for the full six months, thereby slowing the emergence of drug resistance. Only 148 out of 211 countries (45% of the world's population), however, are currently implementing it.
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The WHO estimates that 80% of all TB cases are concentrated in 23 countries, all poor and most in Africa, Asia, and the former Soviet Union - precisely where HIV infection is spreading most rapidly. Opportunities for prevention of both diseases must be exploited simultaneously, requiring close co-operation between TB and AIDS control programs. For example, wider use of anti-retroviral treatment in HIV cases can restore immunity and allow TB treatment to act effectively. But this is possible only if sufficient technical and financial assistance is channeled to poor countries unable to afford anti-retroviral drugs.
Developed countries have a clear interest here. Western Europe thought it defeated TB in the late 1970s, and dismantled its network of dispensaries. In the early 1990s, following a TB resurgence in the US, most West European countries realized that the decline in diagnosed cases had stopped or even reversed, and that they faced new problems owing to increased immigration, HIV infection, and imported multidrug-resistance. Outbreaks of multidrug-resistant TB revived public concern. New control strategies were developed, and surveillance systems were implemented to measure their effectiveness.
But the quality of TB control is still low in much of the world, and TB is a global disease. We cannot control it in one country if there is an outbreak next door. More than 50% of TB cases in many developed countries - Denmark, Israel, Luxembourg, the Netherlands, Norway, Sweden, and Switzerland - are foreign-born. These patients often forgo treatment, and communication with them is difficult. There is thus an urgent need for accessible, culturally sensitive health services that are able to involve community leaders in case management from the first contact to the final cure.
International technical and financial cooperation will ensure that TB expertise is maintained even in countries facing a decline in the number of cases. But donor countries and beneficiaries must first define targets, financial shortfalls, and technical requirements to improve TB control on a global scale. That must mean sharing HIV's more notorious spotlight.