A Visitor From Taiwan

By Joe Levine

There had been early warnings, a few cases reported around the country. But then 44 U.S. Navymen in Key West, Fla., began complaining of sore throats, fever and chills. Last week, after taking throat cultures from the men, doctors confirmed the bad news: Taiwan flu has arrived and begun to take its toll.

Health officials have known of the new viral strain (actually a mutation of Type A influenza strains predominant in the U.S. in the 1950s) only since June, when the first cases were confirmed in Taiwan. Pharmaceutical companies, which had already manufactured a single-shot flu vaccine that is effective against three known and anticipated strains -- A/Chile, A/Mississippi and B/ Ann Arbor -- were forced to rush a separate A/Taiwan vaccine into production. Though no one knows how serious this season's attack will be, influenza generally kills 20,000 to 40,000 Americans in a single winter, more victims than AIDS has claimed since it first appeared.

Despite the quick notoriety that it has gained, Taiwan flu is not considered unusually dangerous. As a close cousin of long-dormant strains, however, it poses a particular threat to people under 35 with chronic health problems; they are not old enough to have developed a strong immunity from previous exposures.

Unfortunately, many of those in need of protection do not get vaccinated. Of the people who are vulnerable to complications from influenza because of other health problems, the U.S. Centers for Disease Control estimates, only one in five will actually bother to get shots. The fact that two kinds of vaccine are necessary for many people this year may be a further source of confusion about who should be inoculated. According to the CDC, the two-shot candidates include anyone under the age of 35 with chronic health problems such as diabetes, heart disease, renal disease, cancer or a suppressed immune response; parents or siblings of children who are at risk; anyone under age 18 who must take aspirin (the combination of aspirin and a viral infection has been linked to a sometimes fatal brain disorder called Reye's syndrome). People over 35 who are at risk and all those over 65 who are otherwise healthy need take only the standard flu shot.

Why is it that flu marches on, while other viral scourges such as polio and measles have been largely conquered in the developed world? The vanquished viruses, it seems, were relatively stable, seldom changing their structure. This enabled their victims, once infected, to develop permanent immunity and allowed scientists to develop vaccines that were effective year after year. The influenza virus, however, is constantly changing the configuration of its surface proteins. Because of these changes, immune-system antibodies, developed in response to either a vaccination or a previous case of flu, fail to recognize and attack the altered virus. As a result, flu -- in ever changing forms -- returns again and again.

To compound the problem, no one knows for sure how the virus circumnavigates the globe in just a few months, although travelers and migrating birds probably help it along. And perhaps because of commercial jets, flu has been spreading more rapidly in recent years, giving health officials even less time to prepare new vaccines. For all these reasons, says University of Pittsburgh Epidemiologist Frederick Ruben, "the only thing that's predictable about influenza is that it's unpredictable."

With reporting by Joyce Leviton/Atlanta