WHOOPING COUGH New cases puzzle experts

The disease can be deadly, especially in babies.
By JANE E. ALLEN
LOS ANGELES TIMES
Doctors and public health officials are stumped. Even though vaccination rates are at record highs for whooping cough, cases of the highly contagious respiratory illness have been on the rise nationwide for more than two decades.
In recent weeks, outbreaks have taken hold in parts of New York, Pennsylvania, Texas and Illinois. Nationally, cases reached 9,771 last year (the most since 1964).
The disease can be deadly, especially in babies, with 22 deaths nationwide last year.
"It's all in infants, which is really tragic," said Dr. Howard Backer, California's top immunization official.
Whooping cough, or pertussis, takes its name from the sound that infected infants make as they struggle to inhale. It's caused by a rugged and wily bacterium, "Bordetella pertussis," that evades much of the body's disease-fighting system while wreaking havoc in the lungs, creating paroxysms of coughing powerful enough to break ribs.
Can be deadly
In infants especially, coughing fits can lead to vomiting, which can cause malnutrition; complications include pneumonia and death. In adults, the illness typically is less severe, producing a cough that lasts weeks to months.
Vaccinations begun in the 1940s was considered to have vanquished the bacterium. It slashed rates from 150 reported cases per 100,000 Americans to less than 1 case per 100,000. But that rate has bounced back to 2.7 reported cases for every 100,000 Americans, although "there may be as many as 10 times as many cases," said Kris Bisgard, a medical epidemiologist with the federal Centers for Disease Control and Prevention in Atlanta.
The illness is likely to be missed in teenagers and adults, who account for 50 percent of reported cases, because few doctors are trained to think about pertussis in anyone but babies. Although a simple blood test could help ensure that cases are properly treated, such a test remains elusive. Nor is there a vaccine for people older than 7.
Health officials understand why some people may be susceptible, but they're at a loss to explain the steady rise in cases. "We're not 100 percent sure what the factors are," Backer said.
Some regional health officials have blamed parents who choose not to vaccinate their children. That has left some children vulnerable to infection and to becoming potent disease-spreaders. Another problem is that the childhood vaccine is imperfect, just 85 percent effective against serious forms of the illness. "That means you can get a mild illness if you're vaccinated and transmit it," said Bisgard.
Another contributor, she said, is waning immunity: The vaccine probably protects for about 10 years, which means kids become susceptible again by adolescence.