The cacophony of coughs you’ll hear in the coming months will be caused by a mix of respiratory bugs. Some are familiar culprits—the common cold, COVID, the flu—and more recently respiratory syncytial virus (RSV). But a growing number of coughs will be caused by the bacterial infection pertussis.
Called whooping cough for its most recognizable symptom, pertussis can be a wretched experience, particularly for babies who aren’t strong enough to withstand the wracking chest spasms. It can put infants in the hospital, although it is very rarely fatal. The pertussis vaccine has been part of the routine child immunization schedule for decades, and cases have dropped about 90 percent from their height during the prevaccine era. The infection’s incidence dropped dramatically with the COVID pandemic, but now cases are rising again, with more than 16,000 reported in the U.S. this year as of September 28. That’s more than four times the total number of cases reported at this time last year.
“The United States is beginning to return to prepandemic patterns, where we typically see more than 10,000 cases of whooping cough reported each year,” says a spokesperson from the Centers for Disease Control and Prevention.
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Here’s what to know about pertussis and how to keep yourself and your family safe from the infection.
What Is Pertussis?
Pertussis is caused by a bacterium called Bordetella pertussis, which easily spreads between people through direct contact or via droplets from someone’s mouth or nose. The bacterium settles into the lining of the respiratory tract, where it produces and emits toxins. These toxins seem to do the most damage in the infection, so receiving antibiotics early, before the bacteria have time to pump out a lot of the poison, is key to managing the disease.
But early treatment is challenging because the first stage of pertussis infection is easy to mistake for other respiratory diseases, says Flor Muñoz, a pediatric infectious diseases expert at Baylor College of Medicine. “You have initially something that looks like a cold, with some congestion, just not feeling well, maybe a sore throat,” she says. In many healthy adults, pertussis may be limited to a lingering cough, while older children may only show nonspecific symptoms, such as a runny nose and a cough, Muñoz adds. “Many times, it’s missed,” she says.
Because whooping cough is very contagious, even those with mild symptoms are able to spread it to particularly vulnerable groups such as young children and elderly people, who are likely to develop more severe cases.
When it progresses into severe disease, pertussis causes violent coughing fits punctuated by a distinct whooping sound caused by inhaling forcefully to try to catch a breath. The coughs between the whoops are brutal, Muñoz says. “They’re unstoppable,” she says. “It’s so forceful that you can actually vomit.”
Very young babies are particularly vulnerable because they can’t yet breathe through their mouth, so the mucus and intense coughing may prevent them from getting enough oxygen. In 2023 more than one in five children under six months old who had pertussis were hospitalized. Treatment often includes intravenous fluids to keep people hydrated, as well as breathing support, Muñoz says.
Even after the whooping cough phase is over, the infection isn’t done. During the recuperation period, people are left with a lingering cough that can last for months, which once gave the infection the nickname “100-day cough.” And starting antibiotics during this stage can’t speed recovery—the bacterial toxins have already run rampant.
Pertussis Case Rates
The total of more than 16,000 cases of pertussis reported to the CDC so far this year is probably lower than the number of infections that are really out there because minor ones are often undiagnosed. New York State, Pennsylvania, Illinois and California have had the highest numbers of reported cases, with more than 1,000 in each state.
Concerningly, the recent rise in pertussis cases isn’t limited to the U.S. England, for example, saw more than 10,000 cases in the first half of 2024 alone, topping more than a decade’s worth of annual totals. “These numbers are big, so it’s not just that we had a deficit [in cases], and now we’re paying for it,” says Pejman Rohani, an epidemiological modeler at the University of Georgia. “I think there’s something happening. I don’t know what that something is.”
In the U.S. during this century, tallies have generally hovered between 10,000 and 20,000, with occasional worse years—notably in 2012, which saw nearly 50,000 cases. A noticeable dip began in 2020, with incidence as low as just more than 2,000 cases in 2021. But with several months of 2024 remaining, rates already match those from a standard full year before the COVID pandemic.
Vaccination against Pertussis
The vaccine that initially made pertussis rates plummet is no longer used because it included the full bacterium and caused rare but serious side effects, such as limpness and convulsions. Since the 1990s the U.S. has instead used what’s called an acellular vaccine, which includes only a handful of the bacterium’s components, such as surface proteins or the pertussis toxin. These materials are combined with tetanus and diphtheria immunizations in two single vaccines: DTaP (which is used for infants older than two months and young children) and Tdap (which is used for older children and adults, and for people in the final trimester of pregnancy).
While safer than the whole-cell version, it’s possible that these newer vaccines don’t provide quite as strong or long-lasting protection, Rohani says, because they don’t include as many parts of the bacterium that could trigger an immune system response. It’s difficult to fully evaluate this concern, he says. But Muñoz says estimates suggest that immunity from either an infection or the vaccine can last about six years. That could open a window for new infections because the U.S. recommends tetanus boosters, either with or without pertussis, only every 10 years.
In the U.S., vaccine uptake is strongest in children, at 94 percent, and teenagers, at 89 percent, according to a CDC spokesperson. Coverage is lower in adults, however. One CDC survey in 2022 suggested that around 40 percent of U.S. adults had gotten a Tdap vaccine or booster in the past 10 years. And only about 55 percent of women who recently had a baby received the Tdap vaccine during their pregnancy, according to another survey conducted in early 2023. Doctors recommend that pregnant people receive a new dose for every pregnancy. Muñoz points to interrupted health care access during the early days of COVID and increased vaccine hesitancy as likely factors for the low vaccination rates in adults.
While these adults may not suffer serious pertussis infections themselves, they risk transmitting the bacterium to more vulnerable children. And the low vaccination rate in pregnant people is even more concerning, Muñoz says. Immunity picked up during gestation is the only protection that babies have until they reach two months of age and can start receiving their own vaccines. “It would not be fair for babies to die of pertussis right now, having the tools that we have,” she says, noting that vaccination works and that health experts have experience bringing it under control. “We have done it before; we have just become too lax.”