Pertussis is at epidemic levels in Washington state, and 19 cases have been reported on Vashon since Dec. 1, when public health officials first noticed an increase in the respiratory illness throughout the county.

No new cases have been reported in April on Vashon, according to Dr. Jeff Duchin, the chief of Communicable Disease Control at Public Health — Seattle & King County. While this is good news, he said, it does not mean that the illness has stopped spreading on the Island, as only a small number of cases are diagnosed and reported.

“It is too soon to tell if this will be a trend or not,” he said.

At the Vashon Island School District, nurse Sarah Day noted that many people have been treated preventatively with antibiotics for the illness, and some have reported they have had it, but follow-up conversations with the health department indicated some of those cases were never confirmed.

While such discrepancies have made the picture confusing at times, she noted, she is pleased that no new cases have been reported in the last two weeks.

“I’m encouraged,” she said.

In March, Dr. Tao Kwan-Gett of the health department noted that Vashon is reporting a higher rate of the disease than other parts of the county. According to Duchin, this finding still holds true, with Vashon reporting more than 10 percent of the cases, though it has less than 1 percent of the population. He believes that statistic represents an accurate reflection of the spread of the disease and is not simply a function of variations in health care on the Island or reporting practices.

“Pertussis is more common in communities with higher exemption rates,” he said.

Of the 19 cases reported on the Island, 17 of them involved people who were not up to date on their pertussis vaccines or were unvaccinated, he said.

With an epidemic of pertussis such as this one, Duchin noted that communities can follow two courses: people can get vaccinated, which will help the epidemic end more quickly and protect them in the future, or they can let the epidemic run its course.

“At some point, the epidemic will die out,” he said. “But pertussis is not going to go away.”

Over a period of time — weeks or months — pertussis will go back to circulating at baseline levels, he said.

Earlier this month, Washington’s Secretary of Health Mary Selecky held a press conference about the spread of the disease in Washington and called for all teens and adults who had not received the Tdap vaccine to obtain a whooping cough booster shot. State Health Officer Dr. Maxine Hayes noted that many adults do not realize they need to be vaccinated or believe they have been, and it is important to be certain.

“We are asking everyone to verify with their health care provider that they’re up to date on vaccines,” she said.

Across Washington, as of April 7, there were 776 reported cases compared to 101 reported cases during the same time period last year.