Less than six months into 2024, Washington has already seen 280 cases of pertussis, the respiratory disease better known as whooping cough. That's over ten times the number of cases, 24, that the state had recorded at this point in 2023, and the highest levels since a spike in late 2019 and early 2020, according to the Washington State Department of Health. It's likely an underestimate — it takes up to three weeks for each case to be recorded.
The numbers include a 62-case outbreak in Chelan County, as well as 73 cases in Clark County.
Is the spike cause for concern, reason to panic or just a fluke? Here's what you need to know.
Pertussis cases are on the rise nationwide
Washington's spike in pertussis cases is part of a nationwide trend. According to the Centers for Disease Control and Prevention, the U.S. has seen three times as many cases as it saw by early June of 2023.
Still, Washington's spike is particularly pronounced. Only six states have seen more cases than Washington, according to CDC data.
Post-pandemic whooping cough spike
According to Eric Chow, the chief of communicable disease epidemiology and immunizations for Seattle and King County, the dramatic rise in pertussis cases is best understood in the context of the COVID-19 pandemic.
"We've been seeing a national increase of pertussis, more commonly known as whooping cough, since the 1980s," Chow said in a video call with McClatchy. "That trend nationally peaked around 2012, and has been staying at a high level until COVID hit."
During the pandemic, Chow said, people were less likely to go to the doctor, meaning fewer cases were detected.
"Reporting probably decreased because of that," Chow said. "More people were masking, more people were social distancing. So cases dropped off quite a bit as a result."
But since pandemic safety measures faded, there have been more opportunities for pertussis to spread.
"As people return to normal activities, as people are traveling more, we're seeing an increase in these types of respiratory diseases," Chow said.
The pandemic also spurred the development of better testing for respiratory illnesses, which Chow said could be a factor in the increase of pertussis cases.
"We're having better PCR tests, or the molecular tests, that have been rolled into these other comprehensive respiratory panels that have come about more commonly as a result of the pandemic."
Is it an epidemic?
The rate of pertussis cases has surpassed the epidemic threshold set by WSDOH. According to Chow, who said he's unfamiliar with exactly how WSDOH came up with that threshold, that primarily means the case count is high enough that the state needs to take proactive steps to stop the disease's spread.
"So usually when we calculate these thresholds, it creates this baseline number, above which is more than what we typically have," Chow said. "It helps with messaging and highlighting the need to take proactive steps to prevent infection in the first place."
Vaccine is available
"Vaccination is our best defense against this pathogen," Chow said.
You could be vaccinated against pertussis without even realizing it — the Tdap vaccine, the common immunization against tetanus, protects against pertussis too.
"People may not realize that it's actually part of the tetanus vaccine, because frequently we think of the tetanus vaccine as tetanus. But Tdap, which has a small 'p' at the end for adults, is a pertussis component," Chow said.
In addition to vaccination, Chow recommends distancing, masking and getting tested at the onset of symptoms.
Children are most vulnerable to pertussis
96 of Washington's pertussis cases have been recorded in children four years old or younger, which is particularly concerning according to Chow.
"Young children, infants under one, are particularly vulnerable to severe disease."
However, there are still steps parents can take to protect young children from whooping cough.
"There is a vaccination schedule for young children," Chow said. "Part of the protection that [the CDC's Advisory Committee on Immunization Practices recommends]... is to make sure that pregnant people, in the third trimester, get a Tdap vaccine. How that plays into all of this is that those antibodies generated by the pregnant individual passes through to the young infant who otherwise would be too young for vaccination but also at the greatest risk for pertussis complications."
In addition to young children, Chow said people with weakened immune systems or respiratory health conditions are at an increased risk of developing complications.
Common pertussis symptoms
Pertussis has similar symptoms to a common cold, but is often marked by "spasms of severe coughing (paroxysms) ending in a gasp, whoop, or vomiting," according to WSDOH. It can be treated with antibiotics and some severe cases require hospitalization, according to the CDC.
Cases by county
Aside from Clark and Chelan, King County has the most cases with 57, followed by Douglas County at 21 and Pierce County at 20.
Thurston County and Whatcom County have each seen two cases, tied for the 14th most of any county, while Benton and Franklin counties have each seen a single case.
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