Sat Apr 27, 2002
By EMMA ROSS, AP Medical Writer
MILAN, Italy (AP) - Whooping cough, largely regarded as an infant disease, is making a global comeback in all age groups, experts said Saturday.
Scientists don't know why but suspect that protection from immunization wears off after a few years and that the bug has outsmarted vaccines used to control it for decades.
Infectious disease specialists meeting in Milan this week said growing numbers of teens, adults and elderly people are carrying the disease unknowingly and spreading it to babies who have not yet been vaccinated.
Whooping cough is caused by the bacteria Bordetella pertussis. It is usually mild in adults but has a high death rate in infants. Until immunization was introduced in the 1940s, whooping cough was one of the most frequent and severe illnesses for infants in many countries.
In nations where the vaccine is not used, whooping cough is still a major cause of death in children, with an estimated 51 million cases and 600,000 deaths annually.
The germ had been well controlled for decades in the industrialized world, but over the last few years the bacteria has begun to strike back in almost all developed countries.
In the United States, there were 7,796 cases in 1996, the highest annual number reported since 1967.
Scientists say that although vaccination works well for young children, the protection doesn't last for life, and no vaccine has been developed for older people.
"We found that after something like 15 years, you may be fully susceptible again, but it may be even shorter," said Dr. Carl Heinz Wirsing von Konig, director of the Institute for Hygeine and Medical Laboratories at the University of Dusseldorf in Germany.
In France, no cases are seen in children between 2 and 8 years old, which indicates that immunity wears off by the time a child is eight. After discovering that, France introduced booster shots at age 11, said Nicole Guiso, director of the National Reference Center for Bordatella at the Pasteur Institute in Paris.
Part of the problem is that much of the rise is being seen among teens and adults.
"The disease is around and it is vastly underreported," von Konig said at the European Congress of Clinical Microbiology and Infectious Diseases.
"What proportion of coughing is pertussis? Irrespective of the country, mostly between 20 and 30 percent of all coughing adults actually have pertussis," he said.
Dr. Joop Schellekens, of the Netherlands National Institute of Public Health, proposed that expectant parents get booster shots in the third trimester of pregnancy to protect babies until they are vaccinated.
In most countries, infants get their first pertussis shot at one month old. They are immunized again at two months, then three months, and given a booster at 15 months.
Whooping cough is more difficult to detect in adults than in children, but von Konig estimated that 80 to 90 percent of people with the disease have a cough that lasts more than three weeks.
It is also characterized by night coughing that disturbs sleep, vomiting, 30-second sweating attacks and complications such as hernias or rib fractures, von Konig said.
In many countries, such as the Netherlands and Canada, outbreaks have occurred despite high vaccination rates.
Recent studies have suggested that the varieties of the pertussis bacteria in circulation today are different than they were in the past. In a Netherlands outbreak in 1996-1997, strains of the bug analyzed were different from the strains used to produce the vaccine in that country.
The same problem has been observed in Canada.
One theory for the resurgence of the disease is that new strains of Bordetella pertussis may have evolved that are resistant to the vaccines used in some countries.
SOURCE: European Congress of Clinical Microbiology and Infectious Diseases.