California has seen a sharp increase in cases of whooping cough, a highly contagious respiratory disease once thought to be nearly eradicated.
State data shows the number of reported cases of whooping cough, also known as pertussis, rose from 1,023 in 2012 to 1,669 last year. About 83 percent of the cases were in children ages 7 to 16, the Sacramento Bee reported Sunday. Ninety-nine patients went to the hospital, but no deaths were reported.
California health officials say one reason for the increase is declining immunity among children who were vaccinated years earlier but haven't gotten the booster shot recommended at ages 11 or 12. Other factors include the disease's cyclical nature and more parents opting out of immunizations for their children.
Caused by a bacterium, whooping cough causes violent coughing that makes it hard to catch one's breath. Coughing spells can last for 10 weeks. It typically affects babies and young children and can be fatal for infants younger than 1 year old.
"Babies who are really young do not have the protection they need against the disease," said Olivia Kasirye, Sacramento County's public health officer. "They depend on the community for the protection."
The Centers for Disease Control and Prevention last year received reports of 48,000 cases of pertussis nationwide last year, more than in any other year after immunizations became widely available.
Nevada County saw the sharpest increase in cases per 100,000 residents, jumping from five in 2012 to 70 cases last year. Marin County ranked second, with 173 cases in 2013.
"Evidence shows that pertussis outbreaks are more likely in communities with clusters of unvaccinated people," said Dr. Ken Cutler, Nevada County's health officer. "It is also clear that people who are unvaccinated are more likely than those who are vaccinated to get pertussis and to have more severe symptoms."
California is one of 20 states that allow parents to exempt their children from public school immunization requirements if they have personal objections.