Whooping cough cases reach highest level in a decade

Whooping cough cases in the U.S. have reached the highest annual total in a decade, with as many cases tallied in the last 12 weeks as in the entire rest of the year.

As of mid-September, about 14,500 cases had been recorded nationwide since the beginning of the year. That number climbed to more than 32,000 as of Dec. 14, according to data from the Centers for Disease Control and Prevention.

That's a six-fold increase from the same time in 2023, when more than 5,100 cases had been recorded. The total for 2022 was even lower, at roughly 3,000 cases.

Experts attribute the high case tally to a combination of factors. For one, whooping cough cases dropped to levels far lower than average during the Covid pandemic, so a jump back to pre-pandemic patterns was expected. However, this year’s total is significantly higher than 2019’s, likely due to waning vaccine protection, lower vaccination rates and improved testing, they said.

Also known as pertussis, whooping cough is a bacterial infection that affects the upper respiratory system. Its spread typically follows a seasonal pattern, with a peak in the fall or winter. 

Early symptoms can resemble a common cold — cough, fever and a runny nose — but after a week or two, patients often develop aggressive cough attacks during which it's difficult to breathe. The term whooping cough is a reference to the high-pitched “whoop” sound that some infected people make as they inhale after a coughing fit.

"They don’t have time in between those coughs to take a breath," said Dean Blumberg, chief of pediatric infectious diseases at University of California, Davis, Children’s Hospital. "Sometimes, if it’s so severe, the kids end up being intubated or on a ventilator so that they can get oxygen."

Infants are the most vulnerable to whooping cough, with the highest risk of getting infected and of serious complications.

“It’s most severe in the youngest kids, so certainly those less than a year, and especially those less than 6 months of age,” Blumberg said. “I personally have seen a patient who’s died from pertussis this year, and I’ve seen several that have been in the ICU.” 

He added that most of the whooping cough patients he's seen have been unvaccinated and that he’s noticed a decline in vaccine coverage.

“We’ve seen more vaccine hesitancy and, unfortunately, we’ve seen more kids who are unimmunized getting pertussis,” Blumberg said.

The CDC recommends whooping cough vaccines, which help protect against pertussis, diphtheria and tetanus, for everyone in the U.S., starting at 2 months old. Infants should get doses of the DTaP shot, as it's known, at 2, 4 and 6 months, followed by booster shots when they are between 12 and 15 months old and again at 4 to 6 years old.

One dose of a different formulation of the shot, the Tdap vaccine, is also recommended for preteens between 11 and 12 and for adults every 10 years.

Whooping cough vaccination rates in the U.S. remain high, but they have declined over the last five years or so. Whereas more than 94% of children born between 2018 and 2019 had received at least three doses of the DTap vaccine by their second birthdays, the rate fell to around 92.5% for those born between 2020 and 2021, according to a CDC report published in September.

Among kindergarteners, the share who had gotten state-required vaccinations — including DTap — fell from 95% in the 2019–20 school year to below 93% for the 2023–24 school year, the CDC found in October.

Of children under 1 who were hospitalized with whooping cough last year, only around 29% had gotten at least three vaccine doses, according to the CDC.

The vaccine's protection fades over time. 

Santina Wheat, a professor at Northwestern University’s Feinberg School of Medicine, said most of the whooping cough patients she’s seen have been vaccinated tweens and adults.

"I think we’re probably seeing some of the impacts of the waning immunity," she said.

Wheat added that an improved ability to diagnose whooping cough is probably also contributing to the United States' higher case total. 

"We now have better testing options, so I'm able to run a panel that looks for a variety of different things, and pertussis is one of those," she said. "Numbers are up, but I also think some of it is just us recognizing it more frequently."

Nonetheless, Blumberg urged parents to take whooping cough's threat seriously and get children vaccinated or boosted. 

“They’ll say, ‘Pertussis is just a cough and kids get over it,” he said, adding: “We need clear and consistent messaging about vaccines. Many people have forgotten about them.”

This article originally appeared on NBCNews.com. Read more from NBC News:

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