The California Department of Public Health (CDPH) is on high alert as it tries to control a whooping cough epidemic that state officials say has already produced 3,834 “confirmed, probable, and suspect cases” of the disease since the the start of 2010.

By this time in 2009, only 530 cases of whooping cough, or pertussis, had been reported for the year in California. But as of Tuesday, the state has recorded seven times as many cases for this year. With three months left in 2010, California is on track to exceed the single-year record number of whooping cough cases recorded in 1958.

There have been eight whooping cough deaths in California this year, all of them of infants under 3 months old. Alameda County has not reported any deaths, and to date has only reported eight hospitalizations, but the threat is still very real to those in the Bay Area. Due to the highly contagious nature of whooping cough and its strikingly similar symptoms to those of the common cold, the Centers for Disease Control (CDC) and the CDPH have issued new vaccination recommendations. Both health agencies are recommending that every California citizen over age 10 receive the whooping cough booster shot, or Tdap, to help increase immunity in the adult population and stop the spread of the disease.

Although infants comprise the largest at-risk group in California, in Alameda County they represent only 7.5 percent of whooping cough cases reported. Locally, the highest case rate has been seen in youths ages 10 to 14 — nearly one quarter of the county’s cases.

With most K-12 schools in Oakland recently starting a new term, “people are worried that when all these kids go back to school they will start coughing, and passing it around,” said Catharine Ratto, an Alameda County Public Health Department nurse who also works with the Immunization Assistance Project, Alameda’s chapter of the California Automated Immunization Registry (CAIR).

Unlike last year, when kids returned to school in the midst of the H1N1, or Swine Flu, outbreak, county schools have reported no increase in absences due to disease. “It is kind of early yet,” said county public health department spokesperson Sherri Willis. Even if there continutes to be no spike in cases now, Willis said, she thinks the start of flu season in December may bring more whooping cough cases.

The start of school is always a dangerous time for the spread of disease, especially among younger children for whom “everything is social and everything is communal,” Willis said. The county health department has prepared letters for school superintendants. The letters are meant to explain, “from a public health standpoint, what we are looking at in terms of flu season 2010,” Willis said. The letter provides parents with information about whooping cough, but leaves the decision about preventative care in the hands of the parents.

Whooping cough symptoms, transmitted through the air, are very similar to those of the common cold or seasonal flu: cough, runny nose, and sneezing, with occasional low fever. Very young infants are the most susceptible to the disease, because they are too young for vaccines and have underdeveloped immune systems. The CDC recommends that children between 2 months and 6 years old receive five doses of DTaP, a vaccine that includes pertussis, diphtheria and tetanus. In California the DTaP vaccine is required for any child enrolling in public school. Children whose parents have filed a personal belief exemption form are exempted.

Though the figures vary by study, research has shown the DTaP vaccine to have a lower efficacy rate than most other common children’s inoculations. The vaccine’s efficacy also lessens over time, so public health departments must now explain to adults, who received the DTaP vaccine as children, that their protection has since decreased and a booster shot may be required.

Although only infants have died since the January onset of the whooping cough surge in California, others have fallen seriously ill. Roughly 12 percent of cases in California—and 4.6 percent of cases in Alameda County—have led to hospitalization. Adults are the primary carriers of the disease, and approximately half of all infants who contract whooping cough catch it from a parent.

Since many infants become infected at home, anyone in daily contact with infants is a prime target for the Tdap booster. This strategy has been named “cocooning”—the idea is to keep infants safe by vaccinating all the adults in their lives.

Health officials are encouraging everyone, not just those in close contact with infants, to get the booster shot, because the disease is so contagious and easily spread. This year, the Tdap booster has been added to the roster of vaccines offered at free back-to-school vaccination clinics throughout the county.

Yet public health officials and nurses like Willis and Ratto agree it’s been difficult to convey the importance of the booster shot for older people. Many parents of young children have heard little about the epidemic or the booster shot. Unlike H1N1, a communicable disease that affected the entire country, whooping cough is a state problem, and there isn’t much money for outreach.

Getting the word out about optional preventative health care is harder than people realize, Willis said. The jumbled shorthand names for the shots don’t help the confusion, she said, any many people don’t even realize that pertussis is another name for whooping cough. “For a while we were using the words Tdap, which is the booster, and DTaP, which is the vaccination series,” she said. “People don’t understand any of that.”

Frances Kaplan, an Oakland resident and mother to two boys, ages 6 and 9, said this week that she hadn’t received a whooping cough booster herself, and that neither her doctor nor her children’s school had provided any information about doing so. Standing outside Dreyer’s ice cream shop in Rockridge, amid a sea of children on a group sugar high, all Kaplan could recall about the disease was an article she read a while back.

“I actually wasn’t sure it was such a big thing,” Kaplan said, and pointed to her children playing with their ice cream-eating friends. “Because I know that they are vaccinated, I haven’t been worrying about it very much.”

Jean Johnstone, an Oakland resident out pushing her 14 month old son in his stroller, said she couldn’t remember his physician giving her any information about whooping cough at her son’s recent one-year check-up. “I vaguely remember hearing about it on the radio,” Johnstone recalled. “There’ve been some outbreaks in California, particularly [in] Hispanic families, but it was in infants that were too young to receive the vaccine.” Johnstone smiled, “I’m impressed I remember that much.” She said her son has already received all five required doses of DTaP.

Even after sending out the “Dear Parent” letter, county health department officials could only hope their warning message “gets trickled down” to the parents it is intended for, Ratto said. The letter is sent only to school superintendents, who must then distribute them out to the principals, who then distribute to the teachers, who then distribute to the parents.

County officials say they are working hard to promote immunization programs. The Alameda Public Health Department, through its Immunization Assistance Project chapter, has developed “a close relationship with all the school districts” in the area, Ratto said. If local schools start to develop whooping cough problems, she said, “the school nurses know to call us.”

For more information on whooping cough in Alameda County, visit the Alameda Public Health Department website.

For complete information on what is happening with the epidemic in the state of California, visit the California Department of Public Health website.

Image: Catharine Ratto (left), a public health nurse, ran a whooping cough vaccination clinic at the North Oakland farmer’s market on Saturday.

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