Whooping Cough

Overview
Epidemiology
Pathophysiology
Etiology and Risk Factors
Clinical Presentation
Diagnosis
Treatment
Complications
Prognosis
Prevention
Recent Research and Advances
Research Papers
Connections
Featured Videos

1. Overview

Whooping cough — known medically as pertussis — is a highly contagious bacterial infection of the airways caused by a bacterium called Bordetella pertussis. It is famous for one feature: a cough so prolonged and severe that it has earned the nickname the “100-day cough.” The classic sound that gives the disease its name is the high-pitched “whoop” — a desperate, crowing gasp for air that some people make at the end of a long coughing fit, when their lungs are finally allowed to refill.

For most healthy older children and adults, pertussis is a miserable but survivable illness: weeks of exhausting coughing fits that disrupt sleep, work, and meals. But for one group — young infants, especially babies under three months old — whooping cough is genuinely dangerous and can be fatal. This page is written for ordinary people who want to understand the disease honestly: how to recognize it, why babies are the central concern, what antibiotics can and cannot do, and why a single vaccine given during pregnancy is one of the most powerful tools we have to keep newborns alive.

Two ideas run through everything below. First, pertussis is badly underrecognized in adults — in a vaccinated grown-up it often looks like nothing more than a lingering cough that won’t quit, with no dramatic whoop at all, so it gets dismissed as a bad cold and quietly spreads. Second, the people most likely to die are the people least able to fight it: newborns who are too young to be vaccinated and who catch the infection from an adult or older sibling who never realized they were contagious. Understanding both of these facts is the key to protecting the most vulnerable.

2. Epidemiology

Pertussis is found everywhere in the world and circulates continuously, with large outbreaks tending to appear in cycles every three to five years. Despite decades of effective vaccination, it has never been eliminated — and in many high-income countries cases have actually been rising over the past two decades. The cyclical pattern is natural: as a wave of infection passes through a population, it temporarily boosts immunity in the people it touches; a few years later, after enough new susceptible people have accumulated (newborns growing up, and adults whose vaccine protection has faded), conditions are ripe for the next outbreak.

The reasons for this resurgence are practical, not political. Two factors stand out. First, the acellular pertussis vaccines introduced in the 1990s — which replaced the older, more reactogenic whole-cell vaccines — are safe and effective but their protection fades faster than expected, leaving older children, teenagers, and adults vulnerable again within several years of their last dose. Second, in some communities vaccine coverage has fallen, which lowers the wall of immunity that normally keeps the bacterium from spreading. Together, waning immunity and gaps in coverage allow B. pertussis to keep finding new susceptible people, producing the cyclical outbreaks we see.

Because vaccinated adults so often have mild, whoop-free illness, the true number of cases is far higher than official counts suggest — many adults are never tested. These quietly infected adults and older siblings are frequently the source of infection for newborns. The hard epidemiological truth is that the great majority of pertussis deaths occur in infants under about three months of age, who are too young to have completed their own vaccine series and who depend entirely on the immunity of the people around them.

3. Pathophysiology

To understand why whooping cough behaves the way it does — especially why the cough drags on for months and why antibiotics often disappoint — it helps to understand what the bacterium actually does inside the airway.

Bordetella pertussis is inhaled in droplets from an infected person’s cough. It then attaches specifically to the cilia — the microscopic, hair-like structures that line the windpipe and bronchi and that normally sweep mucus and debris up and out of the lungs like an escalator. The bacterium releases several toxins; the most important is pertussis toxin. These toxins do two destructive things: they paralyze and damage the cilia, crippling the airway’s self-cleaning system, and they trigger intense local inflammation and a buildup of thick, sticky mucus.

With the cilia knocked out, mucus and dead cells accumulate but cannot be cleared normally. The body’s only remaining way to move the gunk is to cough — violently and repeatedly. This is the mechanical basis of the paroxysmal cough: long bursts of coughing as the body tries, and fails, to clear an airway whose cleaning machinery has been disabled. Crucially, much of the damage and the resulting cough are driven by the toxins, not by living bacteria. By the time the dramatic coughing begins, the bacterial load is often already falling. This is the central reason antibiotics — which kill bacteria — do little to shorten the cough once it is established: the toxin-driven injury is already done.

Pertussis toxin has effects beyond the airway as well. Once absorbed, it interferes with normal signaling in cells throughout the body, which helps explain some of the disease’s odd features — including the very high lymphocyte count seen on blood tests and some of the systemic effects in severely ill infants. In the youngest babies, the picture can be especially dangerous because their airways are tiny and easily plugged with thick mucus, and because the toxin and low oxygen during fits can disturb the immature brain’s control of breathing — one reason newborns may have apnea (breathing pauses) rather than a classic cough. A useful way to picture the whole process: imagine the airway’s cleaning escalator suddenly jamming while the factory keeps producing waste. Pressure builds, and coughing becomes the only release valve — one that has to keep firing until the escalator is slowly rebuilt over many weeks.

4. Etiology and Risk Factors

The cause is a single organism: Bordetella pertussis, a small bacterium that infects only humans. (A related, usually milder species, Bordetella parapertussis, causes a similar but less severe illness.) Pertussis is extraordinarily contagious — among the most transmissible respiratory infections known — spread through airborne droplets when an infected person coughs or sneezes. A single case in a household can infect the great majority of unprotected family members.

The people at highest risk of catching pertussis or of suffering serious harm from it include:

Infants under one year — and especially under three months. This is the central high-risk group. Newborns have not completed (or even started) their vaccine series and have small, fragile airways. They account for the overwhelming majority of hospitalizations and deaths.
Babies whose mothers were not vaccinated during pregnancy, who therefore enter the world without the borrowed maternal antibodies that protect a newborn in the first vulnerable weeks.
Adolescents and adults whose vaccine protection has waned — often a hidden reservoir of mild, unrecognized infection that seeds new cases.
Unvaccinated or under-vaccinated children of any age.
People in close contact with a newborn — parents, grandparents, older siblings, and caregivers — who can carry the infection to the baby.
People who are pregnant, both for their own sake and because their vaccination status directly determines their newborn’s early protection.

5. Clinical Presentation

Classic whooping cough unfolds in three stages. Recognizing them matters, because the disease is most contagious — and most treatable — before it looks like anything serious.

Stage 1 — Catarrhal stage (the “just a cold” phase, about 1–2 weeks)

The illness begins indistinguishably from a common cold: runny nose, sneezing, watery eyes, a mild occasional cough, and little or no fever. This is the cruel part — during this innocent-looking stage the person is at their most contagious, yet almost no one suspects pertussis, so it spreads freely. Antibiotics, if started here, do the most good (both for the patient and for stopping transmission), but the diagnosis is rarely made this early because nothing looks alarming yet.

Stage 2 — Paroxysmal stage (the violent-cough phase, weeks to months)

This is the stage everyone pictures. The cough transforms into sudden, uncontrollable bursts called paroxysms — runs of many rapid coughs, one on top of another, with no chance to breathe in between. At the end of a fit, the person finally drags air back into emptied lungs through a narrowed airway, producing the classic high-pitched inspiratory “whoop.” Coughing fits often end in vomiting (called post-tussive vomiting), leave the person red-faced, sweating, and utterly exhausted, and tend to be worse at night. Between fits, the person can look surprisingly well. These spells can continue for many weeks, even months — hence the “100-day cough.”

It helps to know what a fit is actually like, because it can be frightening to witness in a child. A paroxysm often comes without warning: the person produces a rapid string of coughs — sometimes a dozen or more in a row — bent forward, unable to draw breath, with the face flushing dark red or even bluish as the seconds tick by. Only when the run of coughs finally stops can air rush back in, sometimes with the crowing whoop. Many fits are triggered by ordinary things — laughing, crying, eating, a cold draft, or simply lying down at night. Between attacks the person frequently looks and feels normal, which is part of why the disease is so easy to underestimate until the next fit arrives.

Stage 3 — Convalescent stage (the slow-recovery phase)

Over weeks, the fits gradually become less frequent and less severe. Recovery is slow, and a residual cough can flare up again with later respiratory infections for months afterward. It is normal for the cough to outlast the contagious period by a long margin; a person can be completely non-infectious yet still coughing, because what remains is the slow healing of damaged airways rather than active infection.

Important: it often does NOT look like this

Two groups frequently break the classic pattern, and both are dangerous precisely because the disease is missed:

Adults and previously vaccinated people often have atypical, milder disease — frequently just a prolonged, nagging cough that won’t go away, with no whoop at all. Pertussis is, in fact, an underrecognized cause of chronic cough in adults. Because it’s mistaken for bronchitis or a cold that’s “just hanging on,” these adults keep going to work and visiting family — and unknowingly infect newborns.
Young infants may not cough or whoop at all. This is the single most important warning in this entire article. Instead of the dramatic whoop, a baby with pertussis may have apnea — frightening pauses in breathing — or may turn blue (cyanosis), gag, choke, or simply stop feeding and become limp. A newborn with episodes of stopping breathing, color change, or refusal to feed is a medical emergency — call emergency services and have the baby evaluated immediately. Do not wait for a “whoop” that may never come.

6. Diagnosis

Diagnosis is part clinical suspicion and part laboratory testing. A prolonged cough with paroxysms, whooping, or post-tussive vomiting — or any cough illness in someone exposed to a known case — should raise the possibility of pertussis. Confirmatory tests are chosen based on how long the cough has been present:

PCR (polymerase chain reaction) on a swab from the back of the nose is the main test in the first few weeks of illness. It is fast and sensitive while bacteria are still present in the airway.
Culture (growing the bacterium from a nasal swab) is highly specific and useful early, but it is slow and the bacterium is fastidious and hard to grow.
Serology (blood tests for pertussis antibodies) becomes useful later, several weeks into the illness, once PCR and culture have lost sensitivity — which is often when the patient finally seeks care.

A vital, practical rule: in young infants and other high-risk people, do not wait for test results to act. If pertussis is reasonably suspected, clinicians should begin treatment and protective measures on suspicion, because delays cost lives in babies. Treatment can always be stopped if testing rules it out.

Two other diagnostic realities are worth understanding. First, timing is everything for getting an accurate result: people often don’t suspect pertussis — and don’t seek testing — until the dramatic cough has been going on for weeks, by which point the bacterium may have largely cleared and PCR and culture have lost their punch. That is precisely when serology becomes the more useful tool. Second, a routine blood count in pertussis classically shows a strikingly high number of a particular type of white cell (lymphocytes); in a sick young infant, a very high lymphocyte count is an ominous sign associated with severe disease, and it can be one of the clues that points toward the diagnosis when the cough alone is ambiguous. None of these tests is perfect, which is why clinical judgment — especially around an exposed or vulnerable patient — carries so much weight.

7. Treatment

Treatment of whooping cough has two honest realities that patients deserve to hear up front.

First, the antibiotics. The standard drugs are the macrolide antibiotics — usually azithromycin, sometimes clarithromycin or erythromycin (with azithromycin preferred in young infants for safety reasons). These antibiotics have a clear and important job: they kill the bacteria and quickly make the person non-contagious, which protects everyone around them — above all, any nearby newborns. If antibiotics are started early, during the catarrhal (cold-like) stage, they can also genuinely blunt the illness and shorten its course.

But here is the honest part: once the violent paroxysmal cough is already established, antibiotics do little to relieve the cough itself. As explained above, by that point the misery is driven by toxin damage to the airway, not by living bacteria, and killing the bacteria can’t undo that injury. So patients and families should expect that the cough may persist for weeks even with appropriate antibiotics. The medication is still worth taking — primarily to stop transmission — but it is not a cough cure at that stage. Setting this expectation honestly prevents a great deal of frustration and false hope.

Second, supportive care carries most of the recovery, especially for those well enough to stay home: rest, plenty of fluids, small frequent meals to offset vomiting, humidified air, avoiding cough triggers like smoke, and protecting the household from spread. Cough medicines and over-the-counter remedies are generally not effective for pertussis and are not recommended, particularly in children.

Hospitalization is often necessary for young infants, who can be admitted to monitor for apnea, give oxygen, provide feeding support, and manage complications. Many of the most vulnerable babies are hospitalized purely so that breathing pauses and color changes can be caught and treated instantly. In the sickest infants, intensive-care support — including help with breathing — may be needed during the worst of the paroxysmal stage. For caregivers at home with an older child or adult, the practical goals are simpler: keep the airway calm by minimizing triggers, keep the person hydrated and fed in small amounts, ensure someone is nearby during the worst night-time fits, and know the warning signs that mean it is time to seek urgent care — difficulty breathing between coughs, bluish color, dehydration, or any decline in a young child.

Protecting close contacts (post-exposure prophylaxis). When someone is diagnosed with pertussis, a course of the same macrolide antibiotics is recommended for people in close contact — especially household members, and most urgently anyone living with or caring for a newborn, anyone pregnant, and other high-risk contacts — to stop a chain of transmission before it reaches a baby.

8. Complications

Complications are uncommon in healthy older children and adults but can be serious, and they cluster heavily in young infants. They include:

Pneumonia — the most common serious complication and the leading cause of pertussis-related death, often from a secondary bacterial infection of the damaged lungs.
Apnea — pauses in breathing, especially in young infants; a major reason babies are hospitalized and a direct threat to life.
Seizures and, rarely, encephalopathy (brain dysfunction) in infants, thought to result from a combination of low oxygen during coughing fits and toxin effects; these can cause lasting harm.
Physical injuries from the sheer force of coughing, more common in adults: rib fractures, hernias, urinary incontinence, burst small blood vessels in the eyes, and even fainting from prolonged fits.
Dehydration and weight loss from repeated post-tussive vomiting and difficulty feeding, particularly worrisome in babies.
Exhaustion and sleep deprivation from relentless night-time coughing, which wears down patients and caregivers alike over the long course of illness.

9. Prognosis

For healthy older children, teenagers, and adults, the outlook is good: pertussis is exhausting and prolonged, but full recovery is the rule, even if the cough lingers for weeks or returns briefly with later colds. Serious complications in this group are uncommon.

For young infants, the prognosis is far more serious, and this is where the disease earns its respect. Babies under three months are the group most likely to be hospitalized, to suffer apnea, pneumonia, seizures, or brain injury, and to die. This stark difference in outcome by age is exactly why prevention is aimed so squarely at protecting newborns — through maternal vaccination during pregnancy and through vaccinating the people around the baby. The good news is that these prevention tools are highly effective when used, which is the subject of the next section.

10. Prevention

Prevention is the heart of the pertussis story, and the single most useful thing on this entire page. Because antibiotics do so little once the cough is entrenched, and because the smallest babies are the ones who die, stopping the infection before it reaches a newborn is everything. There are three layered strategies, and they work together.

Childhood vaccination: DTaP

Children are protected with DTaP, a combination vaccine against diphtheria, tetanus, and pertussis, given as a series of doses in infancy and early childhood. This builds a child’s own immunity — but note that the earliest doses don’t start until a baby is a couple of months old, which leaves a vulnerable window in the first weeks of life that childhood vaccination alone cannot close.

Booster doses: Tdap

Because protection from the acellular vaccines wanes over time, immunity must be topped up. A booster called Tdap is given to adolescents and adults. This is not bureaucratic box-ticking — it directly addresses the waning-immunity problem that drives outbreaks. An adult whose protection has faded can both catch pertussis and unknowingly pass it to a baby; a booster narrows that risk.

The most important measure: maternal Tdap in every pregnancy (27–36 weeks)

If you remember only one thing from this page, remember this. Giving the Tdap vaccine to the mother during every pregnancy — ideally between 27 and 36 weeks — is one of the most powerful, best-proven tools we have for keeping newborns alive. When a pregnant person is vaccinated, her body makes pertussis antibodies and passes them across the placenta to her baby. The newborn is then born already carrying protective antibodies, shielding it during exactly the first weeks of life — before it is old enough to be vaccinated itself, and during the period when pertussis is most lethal.

The evidence for this is strong and consistent: large real-world studies have shown that maternal vaccination during pregnancy dramatically reduces pertussis and pertussis deaths in young infants, and the approach has been found safe for both mother and baby. It is recommended in every pregnancy, even pregnancies close together, because antibody levels fade and each baby needs its own fresh supply. This is a rare instance of a simple, safe, one-shot intervention that demonstrably saves the lives of the most vulnerable people there are.

Cocooning: protecting the circle around the baby

The third layer is “cocooning” — making sure everyone who will be close to a newborn is up to date on their pertussis vaccination: the other parent, grandparents, older siblings, babysitters, and caregivers. The idea is to surround the baby with a protective “cocoon” of immune people so that no one in the household is the one who brings the infection home. Cocooning complements maternal vaccination; it does not replace it.

Honest note on waning immunity

It is worth being candid: no pertussis vaccine gives lifelong, perfect protection, and the current acellular vaccines wane faster than older formulations did. This is exactly why boosters and maternal vaccination in every pregnancy matter so much — they compensate for fading immunity and concentrate protection where it counts most. Imperfect protection that fades is still vastly better than no protection at all, and the layered strategy above is what turns an imperfect vaccine into real, life-saving defense for newborns.

Prevention summary

Vaccinate children on schedule with DTaP.
Keep adolescents and adults boosted with Tdap, because protection wanes.
Vaccinate during every pregnancy (Tdap at 27–36 weeks) — the highest-impact single measure for protecting newborns.
Cocoon the newborn by vaccinating everyone in close contact.
Act early on suspicion — seek care, and protect any nearby baby, before the diagnosis is even confirmed.
Treat a newborn’s apnea, color change, or feeding refusal as an emergency.

11. Recent Research and Advances

Pertussis research over the past decade has focused on two practical questions: why is it coming back? and how do we protect newborns better?

On the resurgence, a landmark line of work used a non-human primate (baboon) model to show that the acellular vaccines protect the vaccinated individual from getting sick but do not fully prevent them from being infected and silently transmitting the bacterium to others. That helped explain how outbreaks can persist even in highly vaccinated populations: vaccinated people can become quiet carriers. Parallel epidemiological studies confirmed that protection from the acellular vaccines wanes year by year after the final childhood dose, and that people who received the older whole-cell vaccines in childhood retained stronger, longer-lasting protection — a finding that has reshaped how scientists think about the trade-offs made when whole-cell vaccines were retired.

On protecting newborns, a large body of high-quality real-world evidence has firmly established that maternal vaccination during pregnancy is highly effective and safe — preventing the majority of pertussis cases and deaths in the youngest infants, with reassuring safety data for both mother and baby and no credible link to adverse outcomes such as autism. Refinements continue, including studies on the optimal timing of the maternal dose to maximize the antibodies transferred to the baby (favoring the earlier part of the 27–36 week window). Looking ahead, researchers are working on next-generation pertussis vaccines — including approaches designed to better block transmission and provide longer-lasting immunity — with the explicit goal of closing the gaps that the current acellular vaccines leave open. The thread connecting all of this work is the same priority that runs through this page: keeping B. pertussis away from newborns.

12. References & Research

Historical Background

For centuries, whooping cough was a feared and familiar killer of children, capable of sweeping through communities and claiming infants in large numbers before any treatment existed. The turning point came in the 1940s with the introduction of the first effective whole-cell pertussis vaccine, which produced dramatic and lasting drops in disease and death across the industrialized world. Because the whole-cell vaccine could cause uncomfortable side effects and fueled public concern, it was largely replaced in the 1990s by the gentler acellular pertussis vaccines used today — a change that improved tolerability and acceptance but, as later research revealed, came at the cost of faster-waning protection, a trade-off now understood to contribute to the disease’s modern resurgence. The most recent chapter is the maternal Tdap era: the recognition, backed by strong evidence, that vaccinating during pregnancy passes life-saving antibodies to newborns has become a cornerstone of infant protection worldwide.

Key Research Papers

Amirthalingam G, Andrews N, Campbell H, et al. Effectiveness of maternal pertussis vaccination in England: an observational study. The Lancet. 2014;384(9953):1521–1528.
Klein NP, Bartlett J, Rowhani-Rahbar A, Fireman B, Baxter R. Waning protection after fifth dose of acellular pertussis vaccine in children. New England Journal of Medicine. 2012;367(11):1012–1019.
Tartof SY, Lewis M, Kenyon C, et al. Waning immunity to pertussis following 5 doses of DTaP. Pediatrics. 2013;131(4):e1047–e1052.
Baxter R, Bartlett J, Fireman B, Lewis E, Klein NP. Effectiveness of vaccination during pregnancy to prevent infant pertussis. Pediatrics. 2017;139(5):e20164091.
Donegan K, King B, Bryan P. Safety of pertussis vaccination in pregnant women in UK: observational study. BMJ. 2014;349:g4219.
Becerra-Culqui TA, Getahun D, Chiu V, Sy LS, Tseng HF. Prenatal tetanus, diphtheria, acellular pertussis vaccination and autism spectrum disorder. Pediatrics. 2018;142(3):e20180120.
Witt MA, Arias L, Katz PH, Truong ET, Witt DJ. Reduced risk of pertussis among persons ever vaccinated with whole cell pertussis vaccine compared to recipients of acellular pertussis vaccines in a large US cohort. Clinical Infectious Diseases. 2013;56(9):1248–1254.
Hardy-Fairbanks AJ, Pan SJ, Decker MD, et al. Immune responses in infants whose mothers received Tdap vaccine during pregnancy. The Pediatric Infectious Disease Journal. 2013;32(11):1257–1260.
Altunaiji SM, Kukuruzovic RH, Curtis NC, Massie J. Antibiotics for whooping cough (pertussis). Cochrane Database of Systematic Reviews. 2007;(3):CD004404.
Warfel JM, Zimmerman LI, Merkel TJ. Acellular pertussis vaccines protect against disease but fail to prevent infection and transmission in a nonhuman primate model. Proceedings of the National Academy of Sciences. 2013;111(2):787–792.
Acosta AM, DeBolt C, Tasslimi A, et al. Tdap vaccine effectiveness in adolescents during the 2012 Washington State pertussis epidemic. Pediatrics. 2015;135(6):981–989.
Eberhardt CS, Blanchard-Rohner G, Lemaître B, et al. Maternal immunization earlier in pregnancy maximizes antibody transfer and expected infant seropositivity against pertussis. Clinical Infectious Diseases. 2016;62(7):829–836.
Chiappini E, Stival A, Galli L, de Martino M. Pertussis re-emergence in the post-vaccination era. BMC Infectious Diseases. 2013;13:151.

Research Papers

The following PubMed searches link directly to current, peer-reviewed literature on whooping cough (pertussis). Each opens a live PubMed query in a new tab so you can explore the most recent studies on a given aspect of the disease.

Connections

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