Human illnesses develop resistance to medicine

By Gwynne Dyer

LONDON (JP): Human diseases have evolved in the past, and we are helping them evolve in the present. Which is why our grandchildren may face the same risks from infectious diseases as our grandparents.

A year ago, we got good news about AIDS. A cocktail of three drugs, including new 'protease inhibitors', was restoring even people with full-blown AIDS to normal health -- provided that they could come up with US$25,000 per year, and follow the complicated regime of pill-taking and dietary restrictions that was involved.

There was more rejoicing in San Francisco and London than in Kampala and Bombay, but soon two things started to go wrong even in the richest places.

"The hype about protease drugs has given many people false hope," explained Janet Darbyshire of the British Medical Research Council's HIV Clinical Trials Center at the end of last year. "As a result, there is a serious risk that some may give up safe sex because they think there is nothing left to worry about...."

Worse yet, the HIV virus that causes AIDS was mutating into new strains. "It is very worrying," said Dr. Robert Gallo of the Institute of Human Virology in Baltimore last December. "The most recent information...suggests that between 20 and 30 percent of patients are now infected with viruses resistant to protease inhibitors." Now the evidence is in, and the news is bad.

In early August, the New England Journal of Medicine reported on a small-scale survey of gay men in San Francisco. "Recent advances in treatment are affecting the sexual decision- making" of uninfected gays, it concluded: a quarter of those polled said that they were "less concerned about becoming HIV- positive" because of the new drugs, and a further 13 percent affirmed that "I am more willing to take a chance of getting infected when having sex."

Bad news doesn't travel fast enough -- because August also brought solid evidence that the HIV virus was outwitting the researchers. "There is an increasing percentage of people in whom, after a period of time, the virus breaks through," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland. "People are quite well for six months, eight months, or a year, and after a while, in a significant proportion, the virus starts to come back."

Fauci put the cumulative failure rate of protease inhibitor treatments at up to 50 percent. Since strains of HIV that develop resistance to the new drugs will thrive at the expense of non- resistant strains, the eventual failure rate could be even worse.

This high-speed evolution is very bad news for the more than one million people who will die of AIDS this year. But slower evolutionary processes in other germs and viruses are equally bad news for the three million who will die of tuberculosis (TB) around the world this year, or the two million who die of malaria, or the million who die of hepatitis B. The bugs are adapting to our drugs, and the way we use our drugs isn't helping a bit.

It's new diseases that grab the public's attention, especially the viral hemorrhagic fevers (VHFs) with names straight out of horror movies: Ebola Fever, Rift Valley Fever, Machupo Virus, Sin Nombre Fever, and half a dozen more. They are acutely infectious, cause profuse bleeding from the gums, nose, lungs and intestines, and kill from 25 to 80 percent of those infected.

The real public-health problem of our time is that some of the old mass killers are making a come-back. Not all of them, mercifully, but the slower-moving diseases are doing very well.

The fast killers, paradoxically, are more vulnerable. The last existing samples of the smallpox virus, now confined to test-tubes, are scheduled for destruction in 1999. A mass immunization program in India last year may finally have eradicated polio from the planet (though the World Health Organization will go on vaccinating in suspect areas for another five years to make sure).

Measles, which only 15 years ago was still killing three million children a year, is the next target for global eradication. There are even hopes of ridding the planet of whooping cough, hepatitis and meningitis. But diseases that act slowly, or lie dormant in human hosts for long periods, also have time to develop resistance to our medicines.

A classic example is malaria, where a century of using quinine-based drugs as a prophylactic, in people who did not even have malaria, has fostered the evolution of new strains of quinine-resistant malaria that defy conventional treatment.

Doctors in regions still mostly free of the new strains, like the Amazon, are now giving anti-malaria drugs only to people who actually have malaria, but it's probably too late. In retrospect, it was as stupid as routinely putting low doses of antibiotics into cattle feed (though of course no civilized country would let people act with such criminal irresponsibility for mere profit).

The golden rule is: don't give valuable drugs to people (or cattle) who aren't ill. If they are ill, use enough drugs to kill all the bugs. Don't leave any alive to learn by their experiences.

Not observing that rule is how we got TB back. Seventy-five years ago TB was the greatest killer in urban societies, and then simple antibiotics reduced it to a marginal nuisance. But you must go on taking the drugs for six months to make sure all the TB germs are dead, even though you stop feeling ill long before that.

In millions of cases, people stopped taking antibiotics as soon as they felt better. As a result, we now have strains of TB so drug-resistant that in 1993 the WHO declared a global health emergency, and TB is once again the world's greatest killer.

In half the world's countries you can still buy antibiotics and other life-saving drugs across the counter without a prescription. In the rest, few doctors try to ensure that their prescriptions are used to the last pill. So the global death rate from infectious diseases in 2030 may be closer to that of 1930 than to the present. Pity about the grandchildren.