Pertussis (whooping cough): recognition, treatment, and prevention in Australia

Pertussis in Australian general practice

Pertussis circulates in Australia in endemic fashion with cyclical outbreaks every three to five years. Despite a mature National Immunisation Program, pertussis continues to cause significant illness — particularly in two groups: infants too young to be fully immunised, who face the most severe disease including death; and adolescents and adults whose vaccine-induced immunity has waned, who often have an atypical prolonged cough and unknowingly transmit the infection to vulnerable contacts.

The critical reframe for general practice is that pertussis is primarily dangerous not to the person you see in the consultation room, but to the infant they go home to. The adolescent with a four-week cough who presents hoping for something to help, or the adult with post-tussive vomiting and rib pain, is the source of transmission to a two-month-old. Recognising that transmission chain and acting on it — through azithromycin, notification, and vaccination conversations — is where GP care makes the most difference.

The Australian Immunisation Handbook and CDNA SoNG for pertussis provide the authoritative framework for recognition, management, and public health response.

A. Core clinical — the AU general-practice framework

The three phases of pertussis

Catarrhal phase (1–2 weeks): Presents identically to any upper respiratory tract infection — coryza, low-grade fever, and a mild cough. The critical clinical fact is that this is the peak period of infectivity — the patient is maximally contagious before the diagnostic clinical picture has appeared. Most cases are missed at this stage and treated as routine URTI.

Paroxysmal phase (2–6 weeks): The characteristic clinical picture emerges. Cough becomes paroxysmal — rapid successive coughs within a single expiration, building until the patient is unable to breathe, then followed by a rapid inspiratory gasp that produces the high-pitched “whoop” as air is forced through a narrowed glottis. Post-tussive vomiting (from the effort), cyanosis during paroxysms, and subconjunctival haemorrhages are common. Notably, between paroxysms patients are often entirely well-appearing — a feature that can mislead clinicians into under-estimating the severity.

Convalescent phase (weeks to months): The paroxysmal quality of coughing gradually resolves, but a milder cough often persists for weeks to months — the “100-day cough” of traditional nomenclature. Paroxysms may recur transiently during subsequent respiratory infections for months after the acute illness.

Atypical presentations in adolescents and adults

Waning vaccine-induced immunity means that adolescents and adults routinely develop pertussis without the classic whoop, which requires a narrowed glottis to produce. In vaccinated individuals over 10 years from their last dose, pertussis typically presents as:

• A prolonged cough lasting more than two weeks
• Paroxysmal quality (clustering of coughs)
• Post-tussive vomiting or gagging
• Sleep disruption from cough
• Subconjunctival haemorrhages, rib pain, or urinary incontinence from the coughing effort (in older adults)

Maintaining pertussis in the differential diagnosis of any adult with cough lasting more than two weeks — particularly in households with infants or in healthcare workers — is the key to not missing it.

Infants under 6 months — highest-risk group

Infants in the pre-immunisation window (before the 2-month dose) or incompletely immunised have the most severe pertussis disease. Features in this group may be atypical and alarming:

• Apnoea may be the presenting or predominant feature — even without cough paroxysm
• Cyanosis without the characteristic whoop
• Poor feeding and lethargy
• Rapid deterioration to pulmonary hypertension and cardiovascular collapse

Any infant under 6 months with suspected pertussis should be admitted to hospital for monitoring. The lower threshold for referral is absolute — this is not a condition to manage at home in this age group.

Investigations

Nasopharyngeal PCR — the Royal Children’s Hospital Melbourne clinical guideline and eTG both endorse PCR from nasopharyngeal swab or aspirate as gold standard in the first three weeks. Medicare-rebatable for suspected pertussis. Sensitivity declines significantly after 3 weeks or following antibiotic treatment.

Serology (anti-pertussis toxin IgG) — becomes the preferred investigation after 3–4 weeks when bacterial load has fallen too low for reliable PCR detection. Interpret cautiously within 12 months of dTpa vaccination, as antibody levels from vaccination can produce false positives.

Full blood examination — lymphocytosis (absolute lymphocyte count often >10 × 10⁹/L) is a classic supporting finding in unvaccinated children, though less reliable in vaccinated individuals or adults.

Chest X-ray — typically normal; “shaggy heart border” or perihilar infiltrates suggest secondary pneumonia.

B. Evidence on treatment and prophylaxis

Antibiotic treatment

eTG and AMH both recommend azithromycin as first-line:

Adults and children over 6 months: Azithromycin 500 mg orally on day 1, then 250 mg orally on days 2–5 (5-day course).

Infants 1–6 months: Azithromycin 10 mg/kg orally once daily for 5 days.

Neonates (under 1 month): Azithromycin 10 mg/kg orally once daily for 5 days — preferred over erythromycin in this age group because erythromycin is associated with pyloric stenosis in neonates.

Macrolide allergy alternative: Trimethoprim-sulfamethoxazole 5/25 mg/kg (max 160/800 mg) twice daily for 14 days — not for infants under 2 months or in first-trimester pregnancy.

When treatment helps most: Starting within the catarrhal phase (first 1–2 weeks) can reduce severity and duration. Starting in the early paroxysmal phase reduces transmission substantially but has limited benefit on symptom duration. Starting after 3 weeks of cough has no meaningful symptom benefit but is still worthwhile in households with high-risk contacts to reduce ongoing transmission.

Antibiotic prophylaxis for high-risk close contacts uses the same azithromycin regimen as treatment.

Vaccination — the evidence base

Maternal dTpa vaccination at 20–32 weeks of every pregnancy is supported by RANZCOG and ATAGI with the strongest evidence base of any pertussis prevention intervention. A large 2013 UK study published in the BMJ demonstrated approximately 91% vaccine effectiveness against confirmed pertussis in infants under 3 months of age born to vaccinated mothers. The mechanism is transplacental transfer of maternal IgG antibodies to the fetus — the infant is born with passively transferred protection that bridges the vulnerable pre-immunisation period.

This should be offered in every pregnancy, including to women who received dTpa in a prior pregnancy, because antibody levels wane and each new infant requires fresh transplacental protection. It is funded under the National Immunisation Program.

The cocooning strategy (vaccinating parents, grandparents, and household contacts around a new baby) provides additional protection through reduced transmission from close contacts, though individual efficacy per person vaccinated is lower than the maternal strategy.

National Immunisation Program schedule

The NIP pertussis-containing vaccine schedule:

• Combination dTpa-IPV-HepB-Hib at 2, 4, and 6 months (primary infant series)
• dTpa booster at 18 months and 4 years
• dTpa adolescent booster at 12–13 years (school-based program, funded)
• dTpa every 10 years in adults (recommended; not always funded beyond healthcare workers and pregnancy)

C. Complications

Complications from pertussis cough mechanics are common and should be anticipated:

• Subconjunctival haemorrhages — from raised intrathoracic pressure during paroxysms; benign but alarming to patients
• Rib fractures — particularly in older adults with osteoporosis; can persist as source of cough pain
• Urinary incontinence from paroxysms — common in women
• Secondary bacterial pneumonia — particularly in infants and older adults
• Pneumothorax — rare but documented
• Inguinal hernia — from coughing effort
• Encephalopathy — rare; attributed to hypoxia during cyanotic apnoeic episodes; severe outcome

D. Australian operations

Notification and public health response

Pertussis is a mandatorily notifiable disease in all Australian states and territories under the relevant Public Health Acts. Notification to the state or territory public health unit triggers:

• Formal contact tracing
• Assessment of household contacts for prophylaxis eligibility
• Exclusion advice for workplaces, schools, and childcare centres
• Outbreak investigation in high-risk settings (childcare centres, aged care facilities, hospitals)

Exclusion periods: Exclude from school, childcare, and workplace until 5 days of appropriate antibiotic have been completed; or for 21 days from cough onset if no antibiotic is given. Healthcare workers in high-risk settings (maternity, NICU, paediatric wards) should be excluded and offered prophylaxis.

PBS and MBS

PBS listing for treatment: azithromycin suspension and tablets are PBS General Schedule for the pertussis indication. Trimethoprim-sulfamethoxazole alternatives are also available.

MBS Online items relevant to pertussis management:

• Items 23/36/44 — standard consultation levels
• Item 715 — ATSI Health Assessment (vaccination review)
• Item 10987 — nurse-administered vaccination
• Antenatal consultations (item 16590) — opportunity to discuss and arrange dTpa in pregnancy

Nasopharyngeal PCR for pertussis is Medicare-rebatable; serology is also rebatable.

Consumer resources

The Australian Immunisation Handbook has a comprehensive pertussis chapter with patient-readable information. HealthDirect — Whooping cough and RCH Kids Health Information are useful resources to give to families.

E. Special populations

Pregnant women: Azithromycin is the preferred treatment in pregnancy and is considered safe. Deferring treatment out of antibiotic concerns risks ongoing maternal transmission to the infant at birth — treat promptly. The maternal dTpa should be given at 20–32 weeks; if it was not given during pregnancy, it should be offered immediately postpartum, though this does not provide infant transplacental protection.

Healthcare workers: Those working in maternity, neonatal intensive care, or paediatric settings are a priority for dTpa vaccination and for prophylaxis after exposure. Occupational exposure to pertussis is a workers’ compensation issue in some states if vaccination was not offered.

Immunocompromised individuals: Pertussis may have an atypical prolonged course. Standard antibiotic treatment applies. Vaccination is recommended where appropriate (killed pertussis component in dTpa is safe in immunocompromised individuals).

Older adults: Rib fractures, urinary incontinence, and secondary pneumonia are more common. Cough investigation for pertussis in an older adult with a prolonged paroxysmal cough and no clear alternative diagnosis is appropriate. Offer dTpa booster if not given within 10 years.

Adolescents: Account for a substantial proportion of Australian pertussis cases and are important community sources. The school-based dTpa program at 12–13 years is the key prevention point. Re-vaccinate if the school-based dose was missed.

When to escalate

Escalate immediately (000 or hospital) for:

• Any infant under 6 months with suspected pertussis — admit for monitoring
• Apnoea or cyanosis in any age group
• Respiratory distress beyond what cough mechanics explain (consider secondary pneumonia)
• Suspected encephalopathy (prolonged post-cyanotic confusion or reduced level of consciousness)

Refer to specialist for:

• Outbreaks in institutional settings — state public health unit for coordinated response
• Rib fracture management — general surgeon or respiratory physician
• Severe or refractory bronchospasm — respiratory physician

What this article is and is not

This is general health information drawn from the Australian Immunisation Handbook, CDNA SoNG for pertussis, eTG, AMH, RANZCOG, RCH Melbourne clinical guidelines, and NPS MedicineWise. It is not personal medical advice and does not create a doctor–patient relationship. Pertussis vaccination recommendations may evolve; always check the current Australian Immunisation Handbook for up-to-date schedules.

For consumer information: HealthDirect — Whooping cough, Better Health Channel — Whooping cough. For vaccination queries during pregnancy: discuss with your GP or obstetrician.

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Sources cited

1. Australian Immunisation Handbook — Pertussis
2. CDNA SoNG — Pertussis
3. Therapeutic Guidelines (eTG) — Antibiotic: pertussis
4. Australian Medicines Handbook
5. RANZCOG — Pertussis vaccination in pregnancy
6. ATAGI — Immunisation for pregnant women
7. Royal Children’s Hospital Melbourne — Whooping cough CPG
8. NPS MedicineWise — Pertussis
9. National Immunisation Program — dTpa vaccines
10. MBS Online
11. PBS — azithromycin
12. HealthDirect — Whooping cough
13. Better Health Channel — Whooping cough