Whooping cough outbreaks: Why is pertussis on the rise in several countries?

Cases of whooping cough, or pertussis, have been on the rise in various countries, including the U.K., Australia and China. The U.S. has not seen similar upticks yet, although a few isolated outbreaks have been reported in 2024, as can be expected each year.

Here's what you should know about whooping cough and how to prevent the disease.

Related: Why do coughs linger after a cold?

What is whooping cough?

Whooping cough, also called pertussis, is an infection caused by the bacterium Bordetella pertussis , according to the Centers for Disease Control and Prevention (CDC). The disease gets its name from the characteristic, high-pitched "whoop" sound people with the illness often make when they inhale in the midst of a coughing fit.

B. pertussis invades the airways, latching onto small, hairlike extensions on the surfaces of cells and releasing toxins. According to the medical resource StatPearls , the word "pertussis" derives from the Latin words for "intense cough," and it's also known as the "the cough of 100 days."

Pertussis spreads very easily between people. A measure of the disease's contagiousness, called its basic reproduction number (R0) , is comparable to that of measles — the R0 of pertussis is estimated to be 12 to 17, while the R0 of measles is 12 to 18. The R0 reflects the number of susceptible people that one person infected with a disease would be expected to spread the illness to.

The infection can spread when ann infected person's coughs or sneezes, spewing bacteria into the air. It's thought that people are contagious from the start of their symptoms and for at least two weeks after they begin to cough. However, people with mild symptoms may not realize they have whooping cough and thus may unwittingly spread it to others.

Can adults get whooping cough?

Yes, adults can get whooping cough, and they can spread it to other people; that's why, in countries like the U.S., they're advised to get periodic boosters with a pertussis vaccine. (More information on vaccines can be found in a later section.)

However, adults and teens have a lower risk of serious and deadly complications from pertussis than young children do. About one-third of infants who catch whooping cough need to be hospitalized, and about 1 in 100 of those hospitalized with pertussis die, according to the CDC.

What are the symptoms of whooping cough?

The symptoms of whooping cough typically appear within five to 10 days of a person being exposed to B. pertussis , although they can sometimes take weeks to develop. Early symptoms of the infection can last a week or two and include a runny, stuffy nose; low-grade fever; and mild cough. Then, people can develop "paroxysms of coughing," violent coughing fits that can keep happening for about one to six weeks, and up to 10 weeks in some cases. People often make the characteristic "whooping" sound during these fits.

The coughing may cause people to vomit, fracture a rib, have trouble sleeping and struggle to breathe. Notably, some babies with pertussis don't develop a cough but instead develop apnea, or life-threatening pauses in their breathing. This can cause them to turn blue. Babies with apnea need treatment in a hospital.

Other common complications seen in babies include convulsions and seizures, pneumonia and encephalopathy, broadly meaning brain disease. According to StatPearls, bacterial toxins, a lack of oxygen or blood sugar or bleeding in the brain tied to the increased pressure from coughing may be responsible for these brain-related symptoms.

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Is there a whooping cough vaccine?

Yes, there are several vaccines for whooping cough. One type is known as DTaP vaccines, which protect against diphtheria, tetanus and whooping cough. In the U.S., this type of vaccine is given to children ages 6 and younger. Kids should get five doses of DTaP before their seventh birthday, spaced out according to the CDC's recommended schedule . Children should then get a single dose of a whooping-cough booster, called Tdap, at 11 to 12 years of age.

Adults are recommended to get either a Tdap booster or Td booster (the latter of which protects only against tetanus and diphtheria) every 10 years. Generally, the Tdap booster is specifically recommended for adults who have contact with infants and for health care workers, Mayo Clinic notes . Pregnant people are also recommended to get a Tdap booster during pregnancy , usually early in the third trimester. This provides newborns protection against whooping cough in their first few months of life.

Notably, countries currently experiencing whooping cough outbreaks have different vaccine schedules than the U.S. The U.K. gives kids only four vaccine doses — three when they're infants and one when they're toddlers. The country also recommends the vaccine to pregnant people. In China, children are given three doses before they're 6 months old and then a booster at 18 months; no further boosters are recommended for older age groups. Studies suggest that pertussis vaccines' protection wanes fairly dramatically over time , so a lack of boosters might open the door to outbreaks.

That said, in Australia, the vaccine schedule is somewhat similar to that in the U.S. Children get three doses when they're babies and then boosters at 18 months old, 4 years old and 12 years old. Another booster is given at age 50, and it's also recommended for pregnant people.

Pertussis infections can still happen in people who have been vaccinated, but when they do, the symptoms tend to be milder.

Why are whooping cough cases on the rise in different countries?

Various countries have reported upticks in diagnosed whooping cough cases. For example, between January and early May of this year, the U.K. Health Security Agency has reported more than 2,790 cases, including five that resulted in infant deaths. Major whooping cough outbreaks tend to occur cyclically , every few years, as the pool of newborns with no immunity and people with waning immunity from vaccines or infection grows and shrinks over time; the U.K.'s last peak year was in 2016, when just under 6,000 pertussis cases were reported .

Similar trends have been seen across Europe . China also reported more than 32,380 cases in just January and February — more than the total it saw in all of 2019, Bloomberg reported . As of late May, Australia had seen nearly 7,000 cases , with Queensland and New South Wales hit particularly hard compared with recent years.

There are likely multiple reasons for the rise in cases. One is that, during the peak of the COVID-19 pandemic, precautions taken to slow the spread of the coronavirus also slowed the spread of whooping cough. This lowered the number of cases and thus reduced the number of people who may have gained some natural immunity to the disease through infection.

Childhood vaccination rates fell during the pandemic and are still recovering . Notably, the U.K. reported that whooping cough vaccinations have fallen both in children and among pregnant people in recent years.

Could whooping cough cases rise in the U.S.?

The U.S. hasn't seen an unusual rise in whooping cough cases yet this year. Just prior to the COVID-19 pandemic, the U.S. typically reported between 15,000 and 25,000 pertussis cases a year; 2012 stood out as a bad year, with nearly 48,280 cases. Numbers fell dramatically between 2020 and 2023, with 6,000 or fewer cases each year.

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In 2024, "some U.S. health departments have informed us of local outbreaks, which we expect to see every year," Jasmine Reed, a CDC spokesperson, told NBC News . "So we are not seeing anything unusual." Outbreaks have affected New York City and Hawaii , for example.

As of May 18, the U.S. had reported about 4,500 pertussis cases, according to the CDC's National Notifiable Diseases Surveillance System . By that time last year, only 1,615 cases had been reported. But again, given pre-pandemic rates of the disease, this year's whooping cough rates don't stand out as unusual. The U.S. did see slight dips in pertussis vaccinations among children during the pandemic, but it's not clear whether those could drive a major pertussis spike like those being seen in some other countries.

This article is for informational purposes only and is not meant to offer medical advice.

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