Whooping cough afflicts folk of all ages.

If you thought only children got whooping cough, think again. Researchers report that one in five adults who sought relief for a nagging cough at a Nashville emergency room showed signs of pertussis, or whooping cough.

Indeed, this and other studies suggest that grown-ups could be the main carriers of the disease. That means physicians should be on the alert for children who may have contracted pertussis from an adult, says physician Seth W. Wright of Vanderbilt University Medical Center in Nashville. Wright and his colleagues report the work in the April 5 Journal of the American Medical Association.

For reasons not fully understood, pertussis cases reported to the Centers for Disease Control and Prevention jumped from a low of about 1,000 in 1976 to 6,000 in 1992-1993. Adults and adolescents form a growing proportion of cases -- about 27 percent in 1993. In fact, says Wright, "the number of cases in adults probably dwarfs the number of cases in children. It's just that no one ever knows they have it."

Physicians rarely check adults for whooping cough because "most aren't aware that it's a disease of adults," Wright says. As childhood vaccination fades, adults become susceptible to the disease but often don't show specific symptoms, making diagnosis difficult.

Wright and his colleagues examined 75 people over the age of 18 who went to the Vanderbilt emergency room complaining of a cough that had lasted at least 2 weeks. Blood tests showed that 16 of the 75 had signs of infection with the Bordetella pertussis bacterium.

The findings agree with those of two other recent studies, one of Australians with a chronic cough who visited specialists and another of cough-stricken students at the University of California, Los Angeles. Both studies found pertussis in 26 percent of these adults.

Often, the disease has nearly run its course by the time an adult visits a doctor. Wright recommends that children in the household of an adult with pertussis be treated with antibiotics at the first sign of a cough.

Wright's team also suggests that if further research confirms their results, physicians should consider vaccinating adults for pertussis. Since adults form the disease reservoir, "you might decrease it in adults and thereby decrease it in children," he says.