The pharmaceutical arms race with microbes is unwinnable. We have to learn that successful diseases need us to surviveby Jerome Burne / July 20, 2001 / Leave a comment
imagine what life is like for a virus or bacteria infecting the human body. You have a series of problems. You must get in, evade the sentinels of the immune system, make as many copies of yourself as possible and then, most importantly, get passed on to a new host. Failure at any stage will mean a decline in the numbers of your particular gene combination in the gene pool. Success means that your numbers will grow.
It is not a difficult exercise, yet thinking about microbes in this way has the potential to transform our ideas about diseases and how best to treat them. Paul Ewald, a professor of biology at Amherst College, is one of the few researchers in the world looking at infection from an evolutionary point of view. In his book just published in the US-Plague Time-he claims that the failure of the medical profession to understand the forces involved in pathogen evolution has meant a short-sighted concentration on genetic causes of disease and on ever more powerful drugs. Evolutionary medicine, on the other hand, explains why the influenza pandemic of 1918 is unlikely to happen again and suggests it is possible to domesticate certain microbes so they become less harmful, rather than engaging in an unwinnable pharmaceutical arms race.
“Microbiologists don’t normally think about viruses and bacteria in evolutionary terms,” says Ewald, “which is why they miss something important.” Go back, for a moment, to being a microbe. Let’s suppose you’ve successfully entered your human host and you are reproducing furiously, numbers doubling by the minute. Trouble is, this has a very damaging effect on the body you are in. Your host takes to his bed and within a day or so is dead. This is a disaster for you because you’ve failed the final stage-none of your offspring have gone on to infect anyone else. Now imagine there is a rival strain of your type of infection that doesn’t reproduce so aggressively. Its host doesn’t feel so bad and so dutifully goes in to work where-let’s assume you are an airborne infection, such as flu-he sneezes over dozens of people and infects them.
This trade-off between how aggressive an infection is and how effectively it is passed on, is crucial to Ewald’s ideas about taming pathogens. The simple rule is that when transmission is easy, it pays microbes to reproduce as fast as…