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Pertussis, or whooping cough, is a highly contagious bacterial infection of the airways that causes severe bouts of coughing, sometimes ending in a characteristic "whoop" as the person gasps for breath. It is most dangerous in young babies, who can develop serious breathing problems, but can also cause a prolonged, exhausting cough lasting weeks in older children and adults. Vaccination is highly effective at preventing severe disease and is recommended throughout life, including during each pregnancy to protect newborns.
Definition
Pertussis is an acute, highly contagious respiratory infection caused by the bacterium Bordetella pertussis, characterised by paroxysms — fits — of severe coughing. It is often called the “100-day cough” because of how long the cough persists, and it is a notifiable disease in Australia. Its central clinical paradox is worth stating early: by the time the cough is recognisable as pertussis, antibiotics no longer shorten it, but they still matter for preventing spread.
Pathophysiology
How the infection damages the airway
B. pertussis attaches specifically to the cilia lining the respiratory epithelium and releases a series of toxins — pertussis toxin, tracheal cytotoxin and adenylate cyclase toxin — that paralyse and destroy the cilia, destroy epithelial cells and impair local immune defence. Mucociliary clearance fails, thick secretions accumulate in airways that can no longer move them, and the only remaining clearance mechanism is coughing.1
Why the cough is paroxysmal
The characteristic pattern — a burst of coughs in a single expiration with no chance to breathe in between — reflects the attempt to shift tenacious secretions from a denuded, hypersensitive airway. The whoop is the forceful inspiratory gasp through a narrowed glottis at the end of the paroxysm. Because the airway epithelium takes weeks to regenerate, and cough-receptor sensitivity remains elevated long after the organism has gone, the cough outlasts the infection by a considerable margin.
Why infants are different
Infant airways are small enough that modest secretion and swelling cause significant obstruction, and infants lack the respiratory muscle strength for an effective paroxysm. They therefore frequently present with apnoea, bradycardia and cyanosis rather than a typical cough or whoop — an important trap, since the absence of a whoop is often taken to exclude the diagnosis in exactly the group most at risk.
Co-morbidities
Pertussis is most dangerous in unvaccinated or incompletely vaccinated infants under six months, who carry nearly all of the mortality and are at highest risk of apnoea, secondary pneumonia, pulmonary hypertension, seizures and encephalopathy. Waning immunity means adolescents and adults — even those previously vaccinated — develop milder, atypical disease and become the principal reservoir transmitting to infants. People with underlying COPD, asthma or bronchiectasis experience a more severe and prolonged cough illness, and pertussis is an under-recognised trigger of exacerbation in these groups.
Prevalence
Pertussis persists in cycles of roughly three to five years even in well-vaccinated populations, with periodic epidemics. Notifications in Australia run into the thousands in epidemic years, and rates in adolescents and adults have risen substantially as acellular-vaccine immunity wanes over time. Adult pertussis is significantly under-diagnosed: any adult with a cough persisting beyond two to three weeks, particularly with paroxysms or post-tussive vomiting, warrants consideration regardless of vaccination history.
Causes and risk factors
- Infection with Bordetella pertussis, spread by respiratory droplets. Transmission within a household is highly efficient, with secondary attack rates above 80% in susceptible contacts.
- Infectiousness precedes recognition. The person is most contagious during the early catarrhal phase, when the illness resembles an ordinary cold — so it spreads before anyone suspects it.
- Absent or waning immunity — the principal risk factor. Protection from acellular vaccine wanes over several years, and natural infection does not confer lifelong immunity either.
- Age under six months, especially before the primary course is complete.
- Absence of maternal vaccination in pregnancy, which otherwise transfers protective antibody to the newborn.
Symptoms
The three phases
The catarrhal phase (one to two weeks) resembles a mild cold with runny nose, mild cough and little or no fever — and is the most infectious period. The paroxysmal phase (two to eight weeks, sometimes longer) brings the severe coughing fits, whoop and post-tussive vomiting. The convalescent phase follows over weeks to months, with a gradually improving cough that can flare again with any subsequent respiratory infection.
Adults and older children
Presentation is frequently atypical: a persistent dry cough without a whoop, often worse at night, with sleep disruption and exhaustion, in someone who looks and feels well between bouts. That well-between-paroxysms picture is characteristic and is the reason the diagnosis is so often missed.
Complications of the cough itself
The mechanical force of paroxysms causes rib fractures, intercostal muscle strain, urinary incontinence, inguinal hernia, subconjunctival haemorrhage, cough syncope, and occasionally pneumothorax. These are genuinely disabling in adults and are frequently the reason a patient presents.
Warning signs in infants
Diagnosis
Why diagnosis matters
Diagnosis rarely changes the course of the individual's cough, but it changes everything around them: it triggers isolation, contact tracing, antibiotic prophylaxis for vulnerable household members, exclusion from childcare and school, and public health notification. In an infant it determines admission. Confirming it also ends the diagnostic churn of repeated chest X-rays and asthma trials that adults with unexplained chronic cough often undergo.2
How is it diagnosed?
Clinical suspicion comes from the pattern — paroxysmal cough, whoop, post-tussive vomiting, or apnoea in an infant — particularly with a known contact. PCR on a nasopharyngeal swab is the test of choice and is most sensitive in the first two to three weeks. Culture is more specific but less sensitive and slower. Serology is used later in the illness, beyond two to four weeks, when PCR sensitivity has fallen. A marked lymphocytosis on full blood count is a supporting clue in infants, and a very high white cell count in a young infant is a marker of severe disease.
Investigations for related conditions
Chest X-ray is reserved for suspected pneumonia or pneumothorax rather than performed routinely. In adults with a prolonged cough, the differential includes asthma, upper airway cough syndrome, reflux, ACE-inhibitor cough and tuberculosis, and where cough persists for months after confirmed pertussis, bronchiectasis is considered.
Management
Management and goals
The goals are to limit transmission, protect vulnerable contacts, support the patient through a long and exhausting illness, and recognise deterioration in infants early. Curing the cough is not among them, and saying so honestly at the outset prevents repeated presentations in search of a treatment that does not exist.
Antibiotics
A macrolide — azithromycin, clarithromycin or erythromycin — is given, with trimethoprim-sulfamethoxazole as an alternative. Started in the catarrhal phase, antibiotics reduce severity; started once paroxysms are established, they have little effect on the illness but still render the person non-infectious after five days, which is the reason to give them. Treatment is generally offered within three weeks of cough onset, and within six weeks in infants and pregnancy.
Symptomatic treatment
There is no effective symptomatic treatment for the cough. A systematic review found no evidence of benefit for antihistamines, salbutamol, corticosteroids or pertussis immunoglobulin in reducing paroxysms.3 This matters practically: it prevents repeated ineffective prescribing and redirects the consultation to explanation, sleep, hydration and rib pain.
Hospital care
Infants under six months, and anyone with apnoea, cyanosis, feeding failure or pneumonia, are admitted for monitoring, oxygen, feeding support and nursing through paroxysms. A small number require intensive care, and exchange transfusion is considered in severe infant disease with extreme leucocytosis and pulmonary hypertension.
Prophylaxis and public health
Close contacts — particularly households containing infants, pregnant women in the third trimester, or childcare and healthcare workers with infant contact — are offered antibiotic prophylaxis. Exclusion from school, childcare and work applies until five days of antibiotics are completed or 21 days from cough onset.
Vaccination
Vaccination is the cornerstone of prevention: the routine childhood schedule, adolescent and adult boosters, and — most importantly — a dose in every pregnancy, ideally between 20 and 32 weeks, to transfer antibody before the infant is old enough to be immunised.4 Maternal vaccination is highly effective, reducing confirmed pertussis in infants under three months by around 90% in a large national programme evaluation.5 Boosting household members before a baby arrives — cocooning — supplements but does not replace it.
Medications
Medications for pertussis
Macrolide antibiotics are the only specific treatment, and their purpose is transmission control rather than symptom relief. Analgesia for rib and intercostal pain is genuinely useful and frequently overlooked. Antitussives, bronchodilators and corticosteroids are not recommended in typical pertussis.
Correct use of medications
The antibiotic course is completed even though the cough will not improve, because the five-day threshold governs return to work, school and contact with infants. Macrolides interact with a number of common drugs and prolong the QT interval, which warrants a medication review in older adults. Patients with asthma or COPD continue their usual inhalers and follow their action plan, as pertussis frequently triggers an exacerbation requiring its own treatment.
Living with pertussis
A long and exhausting illness
Weeks of broken sleep, paroxysms that end in vomiting, and exhaustion out of proportion to how well the person appears between bouts. Patients are frequently disbelieved — by employers, by family, sometimes by clinicians — because they look well. Naming the expected duration at diagnosis is one of the more useful steps a clinician can take.
Managing paroxysms
Sitting upright and leaning forward during a bout, small sips of water afterwards, small frequent meals to reduce post-tussive vomiting, and avoiding known triggers such as cold air, smoke, exertion and laughing. Supporting the chest wall with a pillow or the hands reduces rib pain during a paroxysm.
Sleep and rib pain
Night-time paroxysms dominate the illness. Sleeping propped up, adequate analgesia timed for the evening, and a humidified, smoke-free bedroom all help modestly. Rib fracture should be considered where pain is sharply localised and persistent.
Protecting infants
Avoiding contact with babies, pregnant women and immunosuppressed people until non-infectious is the single most important instruction, because infant deaths are concentrated in those infected by a household member — most often a parent or sibling with an unremarkable cough.6 Household vaccination status is checked and updated as part of managing the case.
Work, school and return to activity
Exclusion applies until five days of antibiotics are complete or 21 days from cough onset. Fatigue and exertional coughing often limit work and exercise for longer, and a graded return is more realistic than a fixed date.
Prognosis
Older children and adults recover fully, though the cough commonly persists for two to three months and may recur transiently with subsequent respiratory infections for up to a year. Complications in adults — rib fracture, incontinence, syncope, hernia — are common but resolve. The prognosis in young unvaccinated infants is materially different: they account for almost all hospitalisations and deaths, through apnoea, pneumonia, pulmonary hypertension and encephalopathy. That gradient between adult inconvenience and infant mortality is the entire rationale for maternal vaccination and cocooning.
Role of the physiotherapist
During the acute paroxysmal phase the correct physiotherapy decision is usually not to treat the chest. Percussion, vibration and vigorous clearance provoke further paroxysms, distress the patient and achieve nothing, since the problem is a denuded epithelium rather than retained clearable secretions. Recognising this — and saying so to a referring team — is itself the clinical contribution.
Where the physiotherapist adds value is in the surrounding problems. Rib and intercostal pain limiting breathing depth responds to positioning, supported-cough technique, gentle thoracic mobility and analgesia advice. Secondary complications — pneumonia, atelectasis, exacerbation of an underlying lung condition — are treated on their own merits with airway clearance once the paroxysmal phase settles. Deconditioning after a severe or hospitalised illness is addressed with graded cardiorespiratory rehabilitation.
The most distinctive contribution is in the convalescent phase. A proportion of patients are left with a persistent, hypersensitive cough long after the infection has cleared, and this responds to cough-suppression physiotherapy: education, cough-control techniques, breathing retraining and vocal hygiene, delivered with speech pathology. A multicentre randomised trial showed significant improvement in cough-related quality of life with this approach in refractory chronic cough,7 and combined speech pathology and pharmacological therapy produces further benefit.8 Where cough and sputum persist for months, post-infectious bronchiectasis should be excluded and, if present, managed with regular airway clearance and exercise.9 Finally, physiotherapists are well placed to check household vaccination status and explain why it matters — a small intervention with a disproportionate effect.
Part 1 · References
- Kilgore PE, Salim AM, Zervos MJ, Schmitt HJ. Pertussis: microbiology, disease, treatment, and prevention. Clin Microbiol Rev 2016;29(3):449–486.
- Communicable Diseases Network Australia. Pertussis: CDNA national guidelines for public health units. Canberra: Australian Government Department of Health and Aged Care; 2024.
- Bettiol S, Wang K, Thompson MJ, et al. Symptomatic treatment of the cough in whooping cough. Cochrane Database Syst Rev 2012;(5):CD003257.
- Australian Technical Advisory Group on Immunisation. Australian Immunisation Handbook: pertussis. Canberra: Department of Health and Aged Care; 2025.
- Amirthalingam G, Andrews N, Campbell H, et al. Effectiveness of maternal pertussis vaccination in England: an observational study. Lancet 2014;384(9953):1521–1528.
- Winter K, Zipprich J, Harriman K, et al. Risk factors associated with infant deaths from pertussis: a case-control study. Clin Infect Dis 2015;61(7):1099–1106.
- Chamberlain Mitchell SAF, Garrod R, Clark L, et al. Physiotherapy, and speech and language therapy intervention for patients with refractory chronic cough: a multicentre randomised control trial. Thorax 2017;72(2):129–136.
- Vertigan AE, Kapela SL, Ryan NM, Birring SS, McElduff P, Gibson PG. Pregabalin and speech pathology combination therapy for refractory chronic cough: a randomized controlled trial. Chest 2016;149(3):639–648.
- Hill AT, Sullivan AL, Chalmers JD, et al. British Thoracic Society guideline for bronchiectasis in adults. Thorax 2019;74(Suppl 1):1–69.
References are numbered in citation order (Vancouver/BMJ style) and were current at the time of writing. Guidelines are living documents — verify against the latest version before clinical use.
Clinical evidence
Part 1 covers the same condition without the technical detail. What follows is the evidence base behind it, written for clinicians — the literature, the reasoning and the gaps.
For clinicians: this summary supports clinical reasoning and is not a protocol. Check current guidelines and local policy before applying it, and read it alongside the key references and guidelines directory.
Framing. Pertussis is a vaccine-preventable disease whose management is almost entirely prevention, early antibiotics for transmission control, and supportive care — there is no treatment that shortens the paroxysmal cough once it is established, and no evidence that any intervention, physiotherapy included, changes its course.1,2 Australia runs epidemic cycles every three to four years, and the burden falls hardest on unimmunised and partially immunised infants, in whom apnoea rather than cough is often the presenting problem.3
Prevention and antibiotics
- Maternal vaccination in the third trimester is highly effective at preventing pertussis in infants too young to be immunised — around 90% effectiveness against confirmed infant disease — and is the single most important intervention in this disease.4
- Acellular vaccine protection wanes over several years, which explains adolescent and adult disease and the ongoing need for boosters and cocooning of newborn contacts.3,5
- Macrolide antibiotics reduce transmission and are worthwhile if started in the catarrhal phase, but do not alter symptom duration once paroxysms are established.1
- Symptomatic treatments do not work: the Cochrane review of antihistamines, bronchodilators, corticosteroids and other agents for the cough of pertussis found no evidence of benefit.2
Severe disease and physiotherapy
- Infants under six months carry the risk: apnoea, feeding failure, secondary pneumonia, pulmonary hypertension and extreme leucocytosis mark severe disease, and management is intensive-care supportive.3,6
- Chest physiotherapy is not indicated in pertussis: no evidence of benefit, and handling and airway stimulation can provoke paroxysms and apnoea in infants. Guidance is explicitly to minimise stimulation.2,6
- Cough-related complications in adults — rib fracture, urinary incontinence, syncope, sleep disruption, exhaustion — are frequently what brings the patient to physiotherapy weeks later.5
- Post-infectious cough hypersensitivity is common after a prolonged violent cough illness, and cough-suppression physiotherapy has randomised support in refractory chronic cough — the most useful physiotherapy contribution in this disease.7,8
- Coexisting suppurative lung disease changes the calculus: in bronchiectasis or cystic fibrosis, established clearance regimens continue, modified for cough tolerance.9
Physiotherapy implications
- Decline chest physiotherapy for the acute illness and say why: no benefit, and a real risk of provoking paroxysms and apnoea in infants.2,6
- In infants, minimise handling — cluster cares, avoid suction unless clinically necessary, position for comfort and feeding, and monitor for apnoea and desaturation during and after any intervention.
- Educate the family on trajectory: paroxysms typically peak in the second and third weeks and take weeks to months to settle; expecting this prevents repeated escalations.5
- Treat the cough consequences in adults: cough-suppression techniques, breathing retraining, pelvic-floor assessment for cough-related incontinence, and rib and thoracic pain management.7,8
- Advocate vaccination — maternal dose in pregnancy, on-time infant schedule, adult boosters for those around newborns, and staff immunity in a clinic seeing respiratory patients.3,4
- Observe infection control: droplet precautions until five days of appropriate antibiotics are complete; it is a notifiable disease with contact tracing implications.1
- Escalate apnoea or cyanosis with paroxysms, feeding failure, lethargy, rising oxygen requirement, or any infant under six months with suspected pertussis.
Clinical reasoning
- A cough of more than two weeks with paroxysms, post-tussive vomiting or an inspiratory whoop is pertussis until tested, regardless of vaccination history.5
- An infant with apnoea and poor feeding may have very little cough — do not require the classic presentation before escalating.6
- Deterioration after the first week suggests secondary bacterial pneumonia rather than progression of pertussis itself.
- Persistent cough at eight to twelve weeks with normal investigations is usually cough hypersensitivity, and that responds to physiotherapy where the acute illness did not.7,8
Evidence gaps
- No trial has evaluated any physiotherapy intervention in pertussis; the recommendation not to treat rests on absence of benefit plus plausible harm.2
- Optimal management of the prolonged post-pertussis cough has not been studied specifically.7
- Long-term respiratory consequences of severe infant pertussis, including any link to later airway disease, are poorly defined.
- Duration of protection from current acellular vaccines and the ideal booster schedule remain contested.3
References for the clinical evidence summary
- Communicable Diseases Network Australia. Pertussis: CDNA national guidelines for public health units. Canberra: Australian Government Department of Health and Aged Care; 2024.
- Bettiol S, Wang K, Thompson MJ, et al. Symptomatic treatment of the cough in whooping cough. Cochrane Database Syst Rev 2012;(5):CD003257.
- Australian Technical Advisory Group on Immunisation. Australian Immunisation Handbook: pertussis. Canberra: Department of Health and Aged Care; 2025.
- Amirthalingam G, Andrews N, Campbell H, et al. Effectiveness of maternal pertussis vaccination in England: an observational study. Lancet 2014;384(9953):1521–1528.
- Kilgore PE, Salim AM, Zervos MJ, Schmitt HJ. Pertussis: microbiology, disease, treatment, and prevention. Clin Microbiol Rev 2016;29(3):449–486.
- Winter K, Zipprich J, Harriman K, et al. Risk factors associated with infant deaths from pertussis: a case-control study. Clin Infect Dis 2015;61(7):1099–1106.
- Chamberlain Mitchell SAF, Garrod R, Clark L, et al. Physiotherapy, and speech and language therapy intervention for patients with refractory chronic cough: a multicentre randomised control trial. Thorax 2017;72(2):129–136.
- Vertigan AE, Kapela SL, Ryan NM, Birring SS, McElduff P, Gibson PG. Pregabalin and speech pathology combination therapy for refractory chronic cough: a randomized controlled trial. Chest 2016;149(3):639–648.
- Hill AT, Sullivan AL, Chalmers JD, et al. British Thoracic Society guideline for bronchiectasis in adults. Thorax 2019;74(Suppl 1):1–69.
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