California health authorities say that cases of whooping cough reported to the state have more than doubled so far this year — 346 cases from Jan. 1 to April 30, up from 129 cases during the same period last year.
Four newborns have died from the disease — two in Los Angeles County and two in the Central Valley. Amid concern that this may be the worst year for whooping cough since a 2005 outbreak killed eight infants in California, health officials are recommending a new strategy to protect babies too young for vaccination.
The strategy is called "cocooning" — vaccinating mothers, fathers, grandparents, siblings and anyone else who will be in contact with newborns. It's a relatively new concept because a vaccine for whooping cough, also known as pertussis, first became available for adults and adolescents in 2005.
"If you can't vaccinate the baby, you vaccinate everyone who comes into contact with them," said John Talarico, chief of the immunization branch at the California Department of Public Health.
Babies are vulnerable in their first year of life because they cannot get their first pertussis vaccination until they are at least 6 weeks old. Even then, infants are still at risk because they need several more boosters, said Dr. C. Mary Healy, an expert on pediatric infectious diseases at Texas Children's Hospital in Houston.
Studies show it is family members, particularly mothers, who infect infants with whooping cough, which was a significant killer of infants in the United States until widespread inoculations began in the 1940s.
Though many people were inoculated as children, immunity begins to fade after five years.
One problem in managing this extremely infectious disease is that the telltale "whooping" sound made after a coughing fit does not occur initially. Sometimes, infants with pertussis never make the "whooping" sound.
In infants, "diagnosis of pertussis is often delayed or missed because of a deceivingly mild onset of runny nose," with an undetectable or mild cough, the state said in a recent bulletin to physicians.
Even worse, infants infected with pertussis usually do not have fever, which could leave parents and doctors with a false sense of security that the illness is not severe, said Dr. James D. Cherry, a UCLA pediatrics professor and an expert on pertussis.
The illness in newborns younger than 3 months old can quickly escalate.
"The babies will cough all their air out, the oxygen in the blood will decrease, then they may pass out and they may have seizures, convulsions," Cherry said.
The bacteria can also cause pneumonia and death.
Doctors often don't catch pertussis cases in adolescents and adults, officials said, mistaking the cough for bronchitis or asthma. That's a problem because it increases the chance that an adult can infect a baby.
"It's very subtle early, and people miss it," Cherry said.
State epidemiologist Kathleen Harriman advised new parents to seek medical assistance if an infant has any difficulty breathing.
Health officials urged doctors to order close watch over infants suspected of having pertussis, treat them with the antibiotic azithromycin and consider hospitalization in a facility with access to an intensive care unit.
Cherry said pregnant women in their second and third trimesters can be vaccinated, which extends the protective effect of the vaccine to the fetus.
State officials recently said they would fund hospital vaccinations for mothers immediately after they gave birth and for those who have household contact with newborns.
Officials also urged doctors to report cases to local health departments. In Los Angeles County, there have been 99 possible cases of pertussis so far this year, compared with 155 cases in all of 2009, county health officer Jonathan Fielding said.