Cases of pertussis, also called whooping cough, have surged in California this year, according to the state Department of Health Services.
The state has logged 1,276 cases and four infant deaths through August -- compared with 450 cases and two deaths for the same period in 2004.
The reason for the increase is unclear. Officials say improved testing and diagnosis, rather than an uptick in actual cases, may be behind the change.
“The general consensus is that the increased number of cases is due to better awareness and increased testing,” said Celia Woodfill, an epidemiologist with the state health department. “When the health department finds one case, it keeps investigating. And once you find one case of pertussis, you find more.”
The disease is known for causing severe coughing spells that can last for months. The coughing is accompanied by “whooping” gasps for air. It is spread by coughs and sneezes.
Whooping cough is often misdiagnosed because in its early stages it can resemble a bad cold. Infants, who are most at risk from pertussis, as well as older children and adults, may not make the characteristic whooping sound.
Nationally, the number of pertussis cases rose sharply starting in the 1990s. California’s figures show the state catching up with a national trend.
Health officials nationally have attributed the increase primarily to adults and teenagers who were vaccinated as children and got sick after their immunity wore off. In some cases, they transmitted the disease to young children.
Booster shots for adolescents and adults were recently approved. Health officials recommend that babies be vaccinated five times: at 2, 4 and 6 months, 1 year and 15 months.
The 25,827 cases reported nationwide last year were the highest total since 1959.
Pertussis cases are still dramatically lower than before routine vaccination. In 1934, the nation saw 265,000 cases, the pre-vaccine peak.