THURSDAY, Oct. 12, 2006 (HealthDay News) -- The incidence of whooping cough (pertussis) in the United States is increasing, and health officials need to intensify efforts to re-immunize adolescents and adults with booster vaccines, new research suggests.
The findings, expected to be presented on Oct. 12 at the Infectious Diseases Society of America annual meeting in Toronto, also concluded that too many doctors fail to make the correct diagnosis in people with pertussis.
In the mid-1970s, about 1,000 cases of pertussis were reported each year in the United States. By 2004, more than 25,000 cases were reported. Pertussis can be deadly.
Other studies expected to be presented at the meeting highlight the problem, including the fact the pertussis is more common among minorities, especially Hispanics.
One study showed that the number of pertussis cases in the Seattle area increased from 39 in 2001 to 280 in 2003. The highest incidence of the disease occurred among infants less than 1 year old, but the largest increases in pertussis were among people 20 years and older (an 11-fold increase), and among adolescents and teens 10 to 19 years old (a more than fivefold increase). In 62 percent of infant cases, a household member was the potential source of infection.
"In our study, a third of infants with pertussis were seen by a doctor three times or more before receiving the correct diagnosis. Doctors are just not thinking about whooping cough but they should be, in any person with prolonged cough," study author Dr. Christopher Czaja, an infectious disease fellow at the University of Washington, Seattle, said in a prepared statement.
Another study found there were 160 cases of infant pertussis in the three San Francisco-area counties from 2000 to 2004. Of those 160 cases, 76 (48 percent) occurred among Hispanics. One infant died. In 58 percent of the cases, a parent was the source of infection.
"Pertussis incidence has been increasing for the past decade, but it's really gone up in the last five years. Our research emphasizes that parents and any adult who has contact with an infant needs to have a booster," Kathryn Wymore, surveillance officer for the California Emerging Infections Program, said in a prepared statement.
A third study said there were 409 pertussis cases reported in Philadelphia over a six-year period. Of those cases, 176 (43 percent) were infants, 169 (41.3 percent) were black, and 45 (11 percent) were Hispanic.
"We need to protect the vulnerable infants. Especially in the difficult-to-reach populations, the implementation of adult vaccination has to be really high in order to have a chance of protecting infants," Dr. Irini Daskalaki, a pediatric infectious diseases fellow at St. Christopher's Hospital for Children in Philadelphia, said in a prepared statement.
As infants, most people are vaccinated against pertussis, but the immunity conferred by that vaccination diminishes in adolescence. Booster shots in teens and adults restore that immunity.
A study recently published in the Journal of the American Medical Association found that more and more parents in the United States are refusing to have their children immunized against common childhood diseases, as some states make it easier to evade mandatory requirements. This had led to a higher incidence of pertussis among children, researchers said.
The American Medical Association has more about pertussis.