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July 19, 2002, 8:54PM

Whooping cough cases are on the rise

Vaccination for kids under 7 urged

By LEIGH HOPPER
Copyright 2002 Houston Chronicle Medical Writer

A surge in whooping cough cases, including four infant deaths, has Texas health officials urging parents to make sure babies and children younger than 7 are vaccinated against the disease.

So far this year, there have been 378 reported cases of whooping cough, or pertussis, in the state. Harris County has had 13 confirmed cases, and no deaths. Texas pertussis deaths this year include one in Madison County, two in Webb County and one in the Panhandle area.

"We're having problems in schools, summer camps. We're seeing little outbreaks of disease. Risk of transmission is high," said David Bastis of Texas Department of Health's Immunizations Division.

Whooping cough, marked by a rapid series of coughs followed by a "whoop" as the person gasps for air, is a highly contagious bacterial respiratory illness spread through coughing and sneezing. The illness is most likely to spread in household situations, summer camp cabins and classrooms.

Whooping cough can cause pneumonia, seizures, brain damage and death in infants. Older children, teenagers and adults usually have milder cases of whooping cough, but can transmit the illness to babies who aren't yet protected by the vaccine.

When an infant is hospitalized with pertussis, disease investigators often find the baby has contracted the disease from an older sibling or adult living in the home, said Bastis.

With cases recorded in 41 Texas counties -- many in Central Texas -- the state is part of an unexplained uptick in cases nationwide. About 30 percent of all cases have been in children younger than a year old, according to the Texas Department of Health.

The illnesses are occurring despite a record high in the number of children nationwide vaccinated against pertussis, according to the U.S. Centers for Disease Control and Prevention.

"We've always had outbreaks every three to five years. It's hard to explain how much of this (is due to) increased (reporting) and awareness and how much is a true increase. It's very hard to sort out," said Dr. Kris Bisgard with the CDC's immunization program.

Complete vaccination against pertussis includes four shots, plus a booster, using DTaP, a combination vaccine that also protects against diptheria and tetanus. The first dose is given at 6 weeks to 2 months of age, followed by doses at 4 months, 6 months, 15 to 18 months, and a booster at age 4. The vaccine is not authorized for people 7 and older because the risk of adverse reactions to the shot increases with age.

"We've never had a perfect vaccine. After three doses, it's about 85 percent effective against severe disease," Bisgard said. She said statistics show the initial shots help prevent hospitalization and death in babies.

Dr. Armando Correa, a pediatric infectious disease expert at Baylor College of Medicine, said several factors are contributing to the rise in cases: The vaccine is not available for children age 7 or older; the vaccine's effectiveness diminishes over 10 years after the last dose; a large number of older children and adults have never been vaccinated.

The mixture creates a pool of susceptible people who can then spread the illness to newborns who aren't yet fully protected, he said.

Because the vaccine's effectiveness may fade over time, TDH said doctors should not rule out whooping cough as a possible diagnosis simply because the patient has been vaccinated. TDH is advising physicians to consider giving antibiotics immediately to patients with whooping cough symptoms and to their family members instead of waiting for lab tests to confirm results.

Whooping cough has three stages. The first is marked by runny nose, sneezing, low-grade fever and a mild cough and usually lasts for one to two weeks.

Stage two lasts one to six weeks, and is characterized by prolonged spasms of coughing followed by a high-pitched gasp for air. Vomiting often follows the coughing fits. People usually feel fine between coughing bouts.

In the third stage the coughing spells occur less frequently, but coughing spasms can recur for several months. Someone with whooping cough can infect others throughout their illness.

Last year, 615 cases of whooping cough, including five deaths (none in Harris County), were reported in 70 Texas counties, the highest number of cases since 1968 when 802 cases were reported. The illness has been on an upward trend in the United States for several years.

Between 1990 and 1999, a disproportionate number of pertussis deaths occurred in Hispanic children, the CDC reports. Of 89 infants for whom ethnicity was known, 35 percent were Hispanic.

Disease investigators and public health agencies are conducting studies to identify risk factors for severe and fatal pertussis. A new vaccine for older children and adults should become available in three to five years, Correa said.