Prognosis: Some winter day, a farm worker somewhere who is suffering from ordinary human flu will come in close contact with infected birds and catch avian flu virus from them. Both strains of flu virus will multiply in his cells. Inevitably, in one or more of those cells, the eight segments of the bird virus will get mixed up with the eight strands of the human virus and a new virus with some avian and some human gene segments packaged together will be produced. Most of the flu viruses that will result from random intermingling of avian and human flu genes won't pose a problem because the accidental combinations most often will fail. But sooner or later a new flu virus that incorporates both human infectivity genes and avian virulence genes will emerge as a result of this process of genetic reassortment. And that is the scenario to be anticipated with dread.
What to do: Public health officials already are wisely trying to isolate domestic birds so they are not exposed to the infected wild birds carrying the avian flu virus in ever-widening circles. European countries have started to require that their domestic birds be kept indoors at all times. Additionally, many of those countries have also wisely closed their borders to all bird importation.
Public health officials also should concentrate on immunizing farm workers against conventional human flu, so as to decrease the chance that they will be infected with both avian and human strains of this virus. Realistically, this will be difficult to accomplish. Many farm workers in Asia, Africa, and South America are isolated and hard to reach. And so far, the international funds and the will required for this kind of immunization program have been lacking. But if we can stave off the dangerous genetic reassortment I've described, we might have enough time to develop new vaccines and antivirals in time to stop the global pandemic that a human-to-human strain of avian flu could cause.
Antibacterial soap: Why not to use it
State of the Science: Antibacterial soaps have been very popular with germophobic consumers despite evidence that these antibacterial chemicals don't do anything useful. Readers of this column will remember that giving bars of soap to desperately poor squatters in Karachi made an enormous difference in preventing infectious disease, but it mattered not whether the soap bar was plain or contained an added antibacterial ingredient. Other studies have come to the same conclusion.
The real question isn't whether antibacterial soaps do any good. My guess is that probably about 80 percent (to take a guess) of all nonprescription products don't either. Antibacterial soaps, though, might actively cause harm, as the FDA's Nonprescription Drug Advisory Panel considered last month. Stuart Levy of Tufts University has shown that the use of these products can lead to the development of bacteria that resist their antibacterial effects. And research by others suggests that antibacterial additives to household cleaners can cause germs to become resistant to antibiotics.
Theory: Antibiotics are different in every way—origin, composition, mode of action—from the chemicals we might add to soap to inhibit bacteria. So how could exposure to them suddenly promote resistance to antibiotics? Research by John Beaber, Bianca Hochut, and Matthew Waldor, working together at Tufts, provides an elegant and frightening answer. They found that if even a few bacteria are carrying genes that protect them from antibiotics, physical or chemical damage can trigger them to share that resistance with nearby germs. The bacteria respond to the damage by sending an internal SOS, which activates the bacteria to pass on its antibiotic resistance to other germs it comes in contact with.
Caveat: I began by saying that antibacterial additives sometimes unexpectedly confer protection for bacteria against unrelated antibiotics. And then I talked about how an SOS mechanism can stimulate damaged bacterial cells to pass on bacterial resistance. By putting these two ideas next to each other, I hinted that one thing might explain the other. It might. But honesty compels me to reveal that this is only speculation. We really won't know if antibacterial soap additives set off the chain of events I've described until that experiment is done. Still, I'd avoid antibacterial soaps—at best, they are useless, and at worse they may actually increase the risk of infections that don't respond to treatment with antibiotics.
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