Whooping cough is a highly contagious bacterial infection of the airways caused by the bacterium Bordetella pertussis. It gets its name from the distinctive high-pitched “whoop” sound some people make when gasping for air after a violent coughing fit. The illness can last for weeks or even months, and it poses the greatest danger to infants under one year old. After years of relatively low numbers, whooping cough surged dramatically in 2024, with over 35,000 reported cases in the United States compared to roughly 7,000 in 2023.
How the Infection Works
Bordetella pertussis spreads through respiratory droplets when an infected person coughs, sneezes, or shares breathing space with others. Once inhaled, the bacteria latch onto the tiny hair-like structures (cilia) lining the airways. These cilia normally wave in coordinated patterns to sweep mucus and debris out of the lungs. The bacteria release toxins that paralyze the cilia and trigger inflammation, which means your airways can no longer clear mucus effectively. This buildup of thick mucus is what drives the intense, prolonged coughing fits.
A person is contagious from the moment symptoms first appear and for at least two weeks after coughing starts. Because the earliest symptoms look exactly like a common cold, most people unknowingly spread the infection before anyone suspects whooping cough.
The Three Stages of Symptoms
Whooping cough unfolds in three distinct phases, and the whole illness can stretch across two to three months or longer.
Stage 1: The Cold-Like Phase
The first one to two weeks feel like an ordinary cold: runny nose, mild cough, maybe a low-grade fever. The cough gradually worsens over days. In young infants, this stage may include episodes of apnea, where the baby briefly stops breathing, sometimes before any coughing develops at all. This early phase is the most contagious period and the point when antibiotics are most effective, yet it’s also the hardest stage to distinguish from a regular upper respiratory infection.
Stage 2: The Coughing Fits
After one to two weeks, the mild cough transforms into violent, uncontrollable coughing fits. These paroxysms involve rapid, back-to-back coughs that can leave you unable to breathe until the fit ends with a forceful gasp, producing the characteristic “whoop.” Coughing fits often trigger vomiting, turn the face red or blue from lack of oxygen, and leave the person completely exhausted. On average, these episodes strike about 15 times in a 24-hour period and are typically worse at night.
The fits increase in frequency during the first one to two weeks of this stage, plateau for another two to three weeks, then slowly taper off. Between coughing episodes, a person may feel and appear perfectly fine, which can make the severity of the illness surprising to those who haven’t witnessed a fit.
Stage 3: Recovery
The coughing fits gradually become less frequent and less severe over two to three weeks. Full recovery is slow, though. Paroxysmal coughing can return whenever you catch a subsequent respiratory infection, sometimes for months after the original illness has resolved.
How It Looks Different in Adults
The classic “whoop” is most common in unvaccinated children. Adults and vaccinated individuals often have a very different experience, which is one reason the disease goes unrecognized so frequently in older age groups. A study of adult pertussis patients found that only 8% produced the telltale whooping sound. Instead, the hallmark symptom was a prolonged cough lasting an average of 54 days.
More than half of adults experienced coughing followed by vomiting or choking, and about the same proportion had coughing severe enough to disrupt sleep. Other reported symptoms included sore throat (37%), flu-like body aches (30%), sneezing attacks (22%), hoarseness (18%), and sinus pain (16%). About one in four adults developed complications. Because the presentation so closely mimics a stubborn cold or bronchitis, many adult cases are never diagnosed, allowing the bacteria to silently circulate to more vulnerable people.
Why Infants Are Most at Risk
Whooping cough is most dangerous for babies under 12 months old, particularly those too young to have completed their initial vaccine doses. Among infants hospitalized with pertussis, the complication rates are striking. About two out of three (68%) experience apnea. One in five (22%) develop pneumonia. Seizures occur in roughly 1 in 50 cases, and brain disease from the infection affects about 1 in 150. These complications can be life-threatening, which is why preventive measures focus so heavily on protecting this age group.
In 2024, infants under six months had an incidence rate of 33.4 cases per 100,000, while infants aged 6 to 11 months had the highest rate of any age group at 62.4 per 100,000. By comparison, adults over 20 had a rate of just 2.4 per 100,000.
How Whooping Cough Is Diagnosed
Bacterial culture remains the gold standard for confirming pertussis, but it only works during the first two weeks of coughing, while live bacteria are still present in the airways. A PCR test, which detects the bacteria’s genetic material, has a slightly wider window and can be performed up to three to four weeks after cough onset. Both tests use a swab inserted deep into the back of the nose.
Because testing has time limitations, doctors sometimes diagnose whooping cough based on symptoms alone, especially if a patient has the classic coughing pattern and a known exposure to a confirmed case.
Treatment and Antibiotics
Whooping cough is treated with a class of antibiotics called macrolides. When started early in the illness, ideally during the first cold-like stage, these antibiotics can reduce both the severity of symptoms and the length of time you’re contagious. Once the violent coughing fits are well established, antibiotics do less to shorten the illness but still help prevent spread to others.
Treatment courses are relatively short, typically lasting five to seven days depending on the specific antibiotic prescribed. For infants under one month old, the medication options are more limited because some antibiotics aren’t safe at that age. An alternative antibiotic is available for anyone who can’t tolerate the first-line options.
Beyond antibiotics, there’s no medication that reliably suppresses the coughing fits. Over-the-counter cough medicines are generally ineffective against pertussis. Supportive care, including staying hydrated, eating small meals to reduce post-cough vomiting, and resting in a humidified environment, is the main approach while the illness runs its course.
Protecting Household Contacts
When someone in a household is diagnosed with whooping cough, preventive antibiotics are recommended for everyone living in the home, regardless of vaccination status, as long as it’s been fewer than 21 days since the sick person started coughing. The same preventive treatment is prioritized for anyone at high risk of severe infection, including infants under 12 months and people with conditions that a pertussis infection could worsen.
Pregnant women in their third trimester and people who work in settings with vulnerable populations (like neonatal units or childcare centers) are also candidates for preventive antibiotics after exposure, because they could pass the infection to high-risk individuals.
Vaccination Schedule
The pertussis vaccine is the primary tool for prevention and is given in combination with vaccines for diphtheria and tetanus. Children receive five doses of DTaP at ages 2 months, 4 months, 6 months, 15 to 18 months, and 4 to 6 years. A booster called Tdap, which contains a lower dose of the pertussis component, is recommended at age 11 to 12.
Pregnant women are advised to get a Tdap booster during each pregnancy, typically between weeks 27 and 36 of gestation. This allows the mother to produce antibodies that cross the placenta and give the newborn some protection during the first weeks of life, before the baby is old enough for their own first dose at two months.
Pertussis vaccine protection fades over time. Immunity from the childhood series begins to wane within a few years after the last dose, which helps explain why the largest share of 2024 cases (nearly 43%) occurred in adolescents aged 11 to 19. This age group sits right in the window where childhood vaccine protection is declining and many haven’t yet received their booster.
The 2024 Surge
The jump from about 7,000 cases in 2023 to over 35,000 in 2024 caught public health officials’ attention. Several states were hit particularly hard. Wisconsin reported the highest incidence rate among major states at nearly 45 cases per 100,000 residents, followed by Minnesota at 33 per 100,000. Pennsylvania, Illinois, and Washington each reported more than 2,000 cases.
Pertussis tends to cycle naturally, with peaks every three to five years, partly due to waning immunity in the population. The pandemic years of 2020 through 2022 disrupted normal transmission patterns (fewer people were mixing in schools and workplaces) and reduced routine vaccination rates in some communities. The 2024 spike likely reflects a combination of these cyclical patterns, accumulated susceptibility during the pandemic lull, and fading vaccine protection across age groups.