Whooping cough, known to doctors as pertussis, is a highly contagious bacterial infection of the airways that has staged a striking comeback in recent years. It is caused by the bacterium Bordetella pertussis and is best known for the violent coughing fits that can end in a high-pitched “whoop” as a person struggles to draw breath. In older children and adults the illness is often exhausting but survivable; in young infants it can be life-threatening. This guide explains what whooping cough is, how to recognize its symptoms as they move through three distinct stages, how it spreads, how doctors use swab and blood tests to diagnose it, and what current treatment, prevention, and research have to offer.
What is whooping cough (pertussis)?
Whooping cough is a respiratory infection caused by Bordetella pertussis, a bacterium that fastens onto the tiny hair-like cilia lining the upper airways and releases toxins that inflame and paralyze them. Without those cilia to sweep mucus away, the airways become irritated and clogged, and the body answers with the relentless coughing that gives the disease its name. It is one of the most contagious infections known, and a single untreated person can pass it to many of the unprotected people around them.
The pertussis component of the vaccine is bundled with protection against tetanus and diphtheria in the same childhood and adult shots, so to learn more about one of those companion diseases, see the tetanus symptoms, causes, and treatments guide. After decades of tight control through routine childhood immunization, whooping cough has surged again. The United States reported more than six times as many cases in 2024 as in 2023, exceeding even pre-pandemic 2019 levels, before numbers began easing after a peak in late 2024. Experts link the rebound to normal social mixing resuming after the pandemic, to protection that fades over the years, and to gaps in vaccination.
Symptoms of whooping cough
Whooping cough unfolds slowly, and its symptoms change so much from week to week that the early illness looks nothing like the later one. Doctors describe three stages. The first, called the catarrhal stage, lasts one to two weeks and resembles an ordinary cold, with a runny nose, sneezing, watery eyes, a low-grade fever, and a mild, occasional cough. This is the period when a person is most contagious, and because it is so easily mistaken for a common cold, the diagnosis is often missed at this point; it helps to review the common cold symptoms, causes, and treatments guide.
The second, or paroxysmal, stage is when whooping cough becomes recognizable. Violent, uncontrollable coughing fits arrive in bursts, sometimes a dozen coughs in a single breath, often ending in the telltale whoop as air is dragged back into empty lungs. These fits can trigger vomiting and leave a person exhausted, and they tend to be worse at night. This stage commonly lasts one to six weeks but can stretch to ten. The final convalescent stage is a slow recovery over further weeks, though bouts of coughing may briefly return with the next cold, which is why pertussis is sometimes called the hundred-day cough.
Not everyone follows the classic pattern. Vaccinated teenagers and adults may simply have a nagging cough that outlasts an ordinary chest infection, and the whoop is often absent. Infants may not whoop, or even cough much at all; instead they may have dangerous pauses in breathing, called apnea, that are a medical emergency.
| Stage | What it usually looks like |
|---|---|
| Catarrhal stage (weeks 1 to 2) | Runny nose, sneezing, watery eyes, low-grade fever, and a mild cough; the most contagious period and easily mistaken for a cold |
| Paroxysmal stage (weeks 2 to 8) | Sudden fits of rapid coughing, a high-pitched whoop when breathing in, vomiting after coughing, and exhaustion, often worse at night |
| Convalescent stage (from about week 6) | A slowly improving cough that can flare again with later respiratory infections, the so-called hundred-day cough |
| In young infants | Little or no cough, pauses in breathing (apnea), poor feeding, and a blue or dusky color; always a medical emergency |
How whooping cough spreads: causes and risk factors
The single cause of whooping cough is infection with Bordetella pertussis, and it spreads with remarkable ease. The bacteria travel in the tiny droplets released when an infected person coughs, sneezes, or talks in close quarters, and someone nearby simply breathes them in. A person becomes contagious in the earliest, cold-like stage and can keep spreading the infection for weeks if untreated, which is why outbreaks move quickly through households, classrooms, and childcare settings. Symptoms usually begin about five to ten days after exposure but can take as long as three weeks to appear.
Because immunity from both vaccination and past infection fades over the years, older children and adults whose protection has waned often become the unrecognized source who carries the bacteria home to a newborn. The people at highest risk of severe disease are infants under one year old, especially those too young to have completed their vaccine series. Pregnant people, those with weakened immune systems, and anyone in close contact with a young baby also warrant particular attention. A cough that drags on well past what a routine chest infection would explain can occasionally turn out to be pertussis in an adult, particularly during an outbreak, so to see the difference, review the acute bronchitis symptoms, causes, and treatment guide.
Why whooping cough is dangerous for babies
Whooping cough is most dangerous in the first year of life, and the youngest infants bear the greatest risk. Babies under six months often cannot manage the forceful coughing that clears the airways in older children, so instead of whooping they may stop breathing altogether for short, frightening spells. About one in three infants who catch whooping cough end up in the hospital, and the disease can be fatal in this age group. The most common serious complication is pneumonia, but seizures, brain injury from lack of oxygen, and dehydration from feeding difficulties also occur.
This vulnerability is the reason so much of prevention centers on the people around a newborn. A baby does not begin its own vaccine series until two months of age and is not well protected until several doses are complete, leaving a window in early life when antibodies passed from the mother during pregnancy, and a ring of vaccinated family members, are the main line of defense.
How whooping cough is diagnosed
Because early whooping cough looks like so many other respiratory infections, laboratory testing is what confirms it, and the best test depends on how long the cough has been present. In the first three to four weeks, while bacteria are still present in the airways, clinicians collect a sample from the back of the nose and throat with a thin swab, called a nasopharyngeal specimen. The most sensitive early test is a PCR test, which detects the genetic material of Bordetella pertussis and returns results quickly. A bacterial culture grows the organism from the same kind of sample and is highly specific, but it is slower and less reliable once antibiotics or several weeks have intervened. Later in the illness, once the bacteria have cleared, a blood test for antibodies, known as serology, can support the diagnosis.
Blood work also offers a supporting clue, and it is one place a routine test can point toward whooping cough. In infants and young children the infection often drives up the white blood cell count with a striking excess of one particular type, the lymphocytes, a pattern called lymphocytosis. When a young child is seriously ill, clinicians frequently order and review a complete blood count that tallies the red cells, white cells, and platelets. A markedly high lymphocyte share can raise suspicion of pertussis and, in the sickest infants, signals a higher risk of severe disease, so it can help to understand what a high lymphocyte count means on a blood test. The same report shows the overall white cell tally, and it is worth reading what an elevated white blood cell count can signal on a lab report, because these numbers put the swab results in context rather than replacing them.
| Test | What it detects | Best timing |
|---|---|---|
| Nasopharyngeal PCR | Genetic material of Bordetella pertussis, confirming an active infection | Best in roughly the first three to four weeks of coughing |
| Bacterial culture | Live bacteria grown from a nose-and-throat swab | Early illness, ideally within the first two weeks and before antibiotics |
| Serology (antibody blood test) | The body’s immune response to the bacteria | Later illness, roughly two to eight weeks after the cough begins |
| Complete blood count | A high white cell count with marked lymphocytosis | A supporting clue, mainly in infants and young children |
Treatment and recovery
Treatment for whooping cough centers on antibiotics from the macrolide family, namely azithromycin, clarithromycin, or erythromycin, which clear the bacteria and, just as importantly, stop a person from spreading the infection to others. The catch is timing. Antibiotics work best when started early, in the first week or two before the coughing fits are in full swing. Given later, they do little to shorten the cough, because the damage to the airways has already been done, but they are still worth taking to cut contagiousness. Once someone has completed five days of the right antibiotic, they are generally no longer infectious.
For the cough itself, there is no medicine that reliably switches it off. Over-the-counter cough suppressants have not been shown to help, so care is largely supportive: rest, small and frequent fluids and feedings, a calm and smoke-free environment, and close attention to warning signs. Infants and anyone with severe symptoms may need hospital care to manage breathing, oxygen, and hydration. Because the same antibiotics can protect vulnerable contacts, doctors often prescribe them for close household members, a strategy called post-exposure prophylaxis, even before symptoms appear. Anyone caring for a baby who is coughing in fits, turning blue, or pausing in their breathing should seek emergency care immediately.
Prevention
Vaccination is by far the most effective way to prevent whooping cough, and it works in two directions: protecting the person vaccinated and, through them, the babies who are too young to be fully immunized. Children receive the pertussis vaccine as part of the combined DTaP shot, given in a series that begins at two months of age, while adolescents and adults get a booster called Tdap. Because protection wanes over time, these boosters matter throughout life, not only in childhood.
The single most important step for protecting a newborn is maternal vaccination. Health authorities recommend a Tdap dose during every pregnancy, ideally between 27 and 36 weeks, so that the mother makes protective antibodies and passes them across the placenta to her baby. This maternal dose lowers the risk of whooping cough in babies under two months old, the most dangerous window, by roughly three-quarters. Surrounding a newborn with vaccinated parents, siblings, and caregivers, sometimes called cocooning, adds another layer of protection, as does prompt antibiotic prophylaxis after a known exposure. Whooping cough is one of several vaccine-preventable diseases that have re-emerged where immunization rates have slipped, and for another illness following the same worrying trend, you can see the measles symptoms, causes, and treatment guide.
Complications and long-term outlook
For most vaccinated older children and adults, whooping cough is a long, tiring illness rather than a dangerous one, and a full recovery is the rule even when the cough lingers for weeks. The picture is different for infants, in whom the infection can quickly become severe. The most frequent serious complication is pneumonia, and to understand a lung infection that often follows in the wake of pertussis, review the pneumonia symptoms, causes, and treatment guide. Other complications include prolonged pauses in breathing, seizures, and, rarely, brain damage from oxygen deprivation, along with the physical toll of relentless coughing, which can crack ribs and burst small blood vessels in the eyes.
The outlook depends heavily on age and vaccination status. Deaths are now uncommon and occur almost entirely in young, incompletely vaccinated infants, which is exactly why prevention focused on that group carries so much weight. For everyone else, the main challenge is patience: the cough of pertussis can outlast the infection itself, fading only gradually over the weeks that earned it the nickname of the hundred-day cough.
Latest scientific advances in whooping cough research
The most important recent development is not a new drug but a hard look at why whooping cough came roaring back. A 2025 review in Current Opinion in Pediatrics examined the global resurgence and found that even countries with very high childhood vaccination rates, including the United States, recorded large increases in cases across 2023 and 2024, along with a shift in the disease toward older children and adults whose immunity had waned (Christie, 2025). The review also flagged the spread of Bordetella pertussis strains resistant to the macrolide antibiotics normally used first. What this means for you: whooping cough is circulating more widely than it has in years, so staying current with boosters and taking a lingering cough seriously, especially around infants, matters more now than it did a decade ago.
A 2024 review in Nature Reviews Microbiology traced how the switch decades ago from older whole-cell vaccines to today’s acellular vaccines, which cause fewer side effects, appears to have come at the cost of shorter-lasting protection, letting the bacteria circulate more easily among people whose immunity has faded (Domenech de Cellès and Rohani, 2024). The authors describe how these dynamics, together with the gradual evolution of the bacterium itself, help explain the resurgence. What this means for you: today’s vaccines are safe and still prevent the most severe disease, particularly in babies, but their waning protection is the reason boosters and vaccination during each pregnancy remain essential rather than optional.
Researchers are also working on the next generation of vaccines, designed to last longer and to block transmission rather than only illness. A 2025 review in the Iranian Journal of Immunology summarized several candidates, including live, weakened vaccines given as a nasal spray that aim to build immunity right at the airway surface where the bacteria first take hold (Ehteshaminia et al., 2025). What this means for you: these vaccines are still being studied and are not yet available, so they are a promising glimpse of the future rather than an option today, but they suggest that more durable protection against whooping cough may eventually reach the clinic.
Glossary of key terms
| Term | Definition |
|---|---|
| Bordetella pertussis | The bacterium that causes whooping cough by infecting the lining of the airways. |
| Pertussis | The medical name for whooping cough. |
| Catarrhal stage | The first, cold-like phase of whooping cough, when a person is most contagious. |
| Paroxysmal stage | The phase of severe coughing fits, often ending in the characteristic whoop. |
| Convalescent stage | The gradual recovery phase, when the cough slowly fades over weeks. |
| Apnea | A pause in breathing, a dangerous sign of whooping cough in young infants. |
| Lymphocytosis | A higher-than-normal number of lymphocytes in the blood, a common clue to pertussis in children. |
| Nasopharyngeal swab | A sample taken from the back of the nose and throat to test for the bacteria. |
| DTaP and Tdap | The combination vaccines that protect against diphtheria, tetanus, and pertussis. |
| Post-exposure prophylaxis | Antibiotics given to close contacts of a case to keep them from getting sick. |
Frequently asked questions
What are the first symptoms of whooping cough?
The earliest whooping cough symptoms are mild and easily mistaken for a cold: a runny nose, sneezing, watery eyes, a low-grade fever, and an occasional cough. This first stage lasts one to two weeks, and it is when the infection is most contagious. Only later does the cough build into the severe fits that make pertussis recognizable, which is why an unusual or worsening cough during an outbreak is worth mentioning to a clinician early.
What does whooping cough sound like?
The classic sound is a high-pitched whoop, a gasping intake of breath that follows a long burst of rapid coughing as the lungs refill. Not everyone makes this sound, though. Vaccinated adults often just have a dry, nagging cough, and very young infants may not whoop at all, instead pausing in their breathing. The coughing fits themselves are often severe enough to cause gagging, vomiting, or a red or blue face.
How long is whooping cough contagious?
A person with whooping cough is contagious from the earliest cold-like symptoms and can remain so for about three weeks after the coughing fits begin if they are not treated. Antibiotics shorten this considerably: after five days on the right antibiotic, a person is generally no longer able to spread the infection. This is one reason early treatment matters even when it does not shorten the cough much.
What antibiotics treat whooping cough?
Whooping cough is treated with macrolide antibiotics, usually azithromycin, clarithromycin, or erythromycin. They clear the bacteria and stop the infection from spreading, and they ease the illness most when started in the first week or two. Given later, they mainly reduce contagiousness rather than the cough. Close household contacts are often prescribed the same antibiotics as a preventive measure, even if they feel well.
Who should get the whooping cough vaccine?
Children should receive the DTaP series beginning at two months of age, and adolescents and adults should get a Tdap booster because protection fades over time. A Tdap dose is recommended during every pregnancy, ideally between 27 and 36 weeks, to protect the newborn through antibodies passed across the placenta. Anyone in close contact with a young baby is encouraged to be up to date as well.
How do doctors test for whooping cough?
Doctors confirm whooping cough with a laboratory test on a sample taken from the back of the nose and throat. In the first few weeks of coughing, a PCR test or a bacterial culture can detect the organism directly. Later on, a blood test for antibodies may be used instead. A complete blood count can add a clue, since a very high lymphocyte count is common in infected infants and young children.
Sources
- Centers for Disease Control and Prevention — Pertussis Surveillance and Trends — CDC Whooping Cough, 2025 — cdc.gov
- Centers for Disease Control and Prevention — Tdap Vaccination During Pregnancy — CDC Whooping Cough, 2024 — cdc.gov
- Cleveland Clinic — Whooping Cough (Pertussis): Symptoms and Treatment — Cleveland Clinic Health Library, 2024 — my.clevelandclinic.org
- Mayo Clinic — Whooping Cough: Symptoms and Causes — Mayo Clinic, 2024 — mayoclinic.org
- MedlinePlus, National Library of Medicine — Whooping Cough — MedlinePlus Health Topics, reviewed 2024 — medlineplus.gov
- Christie C — Resurgence of pertussis: whopping the ‘100-day cough’ — Current Opinion in Pediatrics, 2025 — doi.org/10.1097/MOP.0000000000001486
- Domenech de Cellès M, Rohani P — Pertussis vaccines, epidemiology and evolution — Nature Reviews Microbiology, 2024 — doi.org/10.1038/s41579-024-01064-8
- Ehteshaminia Y, Golsaz-Shirazi F, Amiri MM, Shokri F — Next-generation Pertussis Vaccines with Special Focus on Intranasal Vaccination — Iranian Journal of Immunology, 2025 — doi.org/10.22034/iji.2025.108179.3088
Further reading
- Compare whooping cough with another contagious respiratory illness by exploring the flu symptoms, causes, and treatment options.
- Understand a different cause of a long-lasting cough by reading this guide to chronic bronchitis symptoms, causes, and treatments.
- See how another type of white blood cell appears on a count by reviewing what neutrophils reveal on your blood results.
- Learn how antibody testing reflects past infection or vaccination by reading what IgG antibodies reveal on a blood test.
- Build a fuller picture of your own numbers with this guide to reading reference ranges, flags, and trends in a lab report.
Understand your lab results with BloodSense
Whooping cough is confirmed and tracked through laboratory testing, from the nasopharyngeal PCR and culture that catch the bacteria early to the antibody tests and blood counts that fill in the picture later. Those same results, whether a white cell count, a lymphocyte share, or an antibody level, can be hard to make sense of on your own, especially when a report is full of reference ranges and flags.
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