ontacts independent of symptoms," Dr. Van Rie said, "and therefore our conclusions do not have the bias of incomplete information. Our study confirms that parents are an important source for infant pertussis."

Children with pertussis almost always suffer its vivid symptoms --

The New York Times reported, in an April 2007 article, that the rates of pertussis, or whooping cough, have been steadily increasing since the 1980s, and a new study by the Centers for Disease Control and Prevention (CDC) reports that infants most often catch the disease from older household members, especially infected parents. Adults in Dallas, Houston and elsewhere in Texas, as well as throughout the rest of the country, can transmit the illness without having any symptoms themselves.

There were more than 25,000 cases reported in 2005, the latest year for which there are figures, up from an average of 2,900 a year in the 1990s. The panel that advises the CDC now recommends vaccination for all adolescents and adults up to 64, and for older people if they have close contact with babies. While the disease is usually mild in adults, it can be fatal in infants.

"The big problem in previous studies was that they looked at those who had symptoms, and then extrapolated from them to people for whom they had no information," said Dr. Annelies Van Rie, the senior author.

"We had information on all close contacts independent of symptoms," Dr. Van Rie said, "and therefore our conclusions do not have the bias of incomplete information. Our study confirms that parents are an important source for infant pertussis."

Children with pertussis almost always suffer its vivid symptoms --

household members, especially infected parents. Adults in Dallas, Houston and elsewhere in Texas, as well as throughout the rest of the country, can transmit the illness without having any symptoms themselves.

There were more than 25,000 cases reported in 2005, the latest year for which there are figures, up from an average of 2,900 a year in the 1990s. The panel that advises the CDC now recommends vaccination for all adolescents and adults up to 64, and for older people if they have close contact with babies. While the disease is usually mild in adults, it can be fatal in infants.

"The big problem in previous studies was that they looked at those who had symptoms, and then extrapolated from them to people for whom they had no information," said Dr. Annelies Van Rie, the senior author.

"We had information on all close contacts independent of symptoms," Dr. Van Rie said, "and therefore our conclusions do not have the bias of incomplete information. Our study confirms that parents are an important source for infant pertussis."

Children with pertussis almost always suffer its vivid symptoms --

for which there are figures, up from an average of 2,900 a year in the 1990s. The panel that advises the CDC now recommends vaccination for all adolescents and adults up to 64, and for older people if they have close contact with babies. While the disease is usually mild in adults, it can be fatal in infants.

"The big problem in previous studies was that they looked at those who had symptoms, and then extrapolated from them to people for whom they had no information," said Dr. Annelies Van Rie, the senior author.

"We had information on all close contacts independent of symptoms," Dr. Van Rie said, "and therefore our conclusions do not have the bias of incomplete information. Our study confirms that parents are an important source for infant pertussis."

Children with pertussis almost always suffer its vivid symptoms --

it can be fatal in infants.

"The big problem in previous studies was that they looked at those who had symptoms, and then extrapolated from them to people for whom they had no information," said Dr. Annelies Van Rie, the senior author.

"We had information on all close contacts independent of symptoms," Dr. Van Rie said, "and therefore our conclusions do not have the bias of incomplete information. Our study confirms that parents are an important source for infant pertussis."

Children with pertussis almost always suffer its vivid symptoms --

ontacts independent of symptoms," Dr. Van Rie said, "and therefore our conclusions do not have the bias of incomplete information. Our study confirms that parents are an important source for infant pertussis."

Children with pertussis almost always suffer its vivid symptoms -- bouts of violent coughing, followed by gasping for breath with a characteristic high-pitched whoop. Young infants appear especially ill and distressed, sometimes even turning blue as they gasp for air, and then vomiting after the coughing episode. The disease is spread by contact with airborne droplets from coughing or sneezing.

The researchers tracked 91 cases of pertussis in infants less than 6 months old in 12 hospitals in France, Germany, the United States and Canada. They also examined 347 of the infants' contacts, and found that 76 percent to 83 percent of the transmissions to infants could be attributed to a household member. Half the infections were from parent to child.

Dr. Margaret K. Hostetter, who leads the department of pediatrics at Yale University, was impressed with the study's methodology and said it reinforced the case for early vaccination.

"Sometimes we think waiting a month or two beyond the appropriate time for the immunization isn't a big deal," she said. "This study shows that those very early months are extremely important for a baby's protection." Dr. Hostetter was not in