LIKE every dog, every disease now seems to have its day. World Tuberculosis Day is on Saturday March 24th. On the same day in 1882 Robert Koch, a German bacteriologist, presented his discovery of Mycobacterium tuberculosis to a meeting in Berlin. That announcement helped to establish the germ theory of disease—the idea that contagious illnesses are caused by specific micro-organisms.
Tuberculosis was once terribly fashionable. Dying of “consumption” seems to have been a favourite activity of garrett-dwelling 19th-century artists. It has, however, been neglected of late. Researchers in the field never tire of pointing out that TB kills a lot of people. According to figures released earlier this week by the World Health Organisation, 1.6m died of the disease in 2005, compared with about 3m for AIDS and 1m for malaria. But it receives only a fraction of the research budget devoted to AIDS. America's National Institutes of Health, for example, spends 20 times as much on AIDS as on TB. Nevertheless, everyone seems to getting in on the TB-day act this year.
The Global Fund, an international organisation responsible for fighting all three diseases, but best known for its work on AIDS, has used the occasion to trumpet its tuberculosis projects. The fund claims that its anti-TB activities since it opened for business in 2002 have saved the lives of over 1m people. The World Health Organisation has issued a door-stop report that no-one will ever read from cover to cover. This, too, contains some good news. Although the number of TB cases is still rising (up by 70,000 between 2004 and 2005), the rate of illness (ie, the number of cases per head of population) seems to have stabilised; the caseload, in other words, is growing only because the population itself is going up.
Even drug companies are involved. In the run-up to the day itself, Eli Lilly announced a $50m boost to its MDR-TB Global Partnership. MDR stands for multi-drug resistance, and it is one of the reasons why TB is back in the limelight. Careless treatment has caused drug-resistant strains to evolve all over the world. The course of drugs needed to clear the disease completely takes six months, and persuading people to stay that course once their symptoms have gone is hard. Unfortunately, those infected with MDR have to be treated with less effective, more poisonous and more costly drugs. Naturally, these provoke still more non-compliance and thus still more evolution.
As a result, the world is seeing the rise of extremely drug resistant (XDR) strains that kill almost everyone in whom they take hold. A WHO survey conducted between 2000 and 2004 suggested that 20% of cases were MDR and 2% XDR. Lilly's contribution to the common weal is the transfer to manufacturers in badly affected countries of the technological tricks needed to make two antibiotics that do generally work against MDR-TB (though not against XDR-TB).
The lack of effective anti-TB drugs is also being addressed by trying to invent new ones. Until recently, this would have been anathema to drug companies. Creating treatments for infectious diseases of the poor is not an obvious way to riches and happy shareholders. Recently, however, firms have been able to offload some of the development costs on to philanthropic organisations such as the Gates Foundation. As a result, seven potential anti-TB drugs are now in clinical trials and around 20 more are under investigation.
The other reason TB is back is its relationship to AIDS. The Global Fund's joint responsibility for the diseases is no coincidence. AIDS does not kill directly. Rather, HIV, the virus that causes it, weakens the body's immune system and exposes the sufferer to secondary infections. Of these, TB is one of the most serious. It kills 200,000 AIDS patients a year. However, some anti-TB drugs interfere with the effect of some anti-HIV drugs. Conversely, in about 20% of cases where a patient has both diseases, anti-HIV drugs make the tuberculosis worse. The upshot is that 125 years after Koch worked out what caused TB, it is still a serious threat. It is good to be reminded of that occasionally.