Pertussis

Definition

• Acute, highly contagious respiratory infection caused by Bordetella pertussis

• Characterised by a prolonged cough that may include paroxysms, inspiratory whoop and post-tussive vomiting

• Particularly severe in infants, with higher risk of complications such as apnoea, pneumonia, encephalopathy and death

Key Stages

• Incubation: Typically 10–14 days, although clinical symptoms may not appear until 1–3 weeks after exposure

• Catarrhal Stage: Mild upper respiratory tract infection with fever, malaise, dry cough and runny nose lasting 1–2 weeks

• Paroxysmal Stage: Marked by severe, repetitive cough paroxysms, often with an inspiratory whoop and post-tussive vomiting, lasting 2–6 weeks

• Convalescent Stage: Gradual resolution of symptoms that may persist for weeks to months

Close Contacts

• Defined as individuals within 1 metre for more than 1 hour during the infectious period

• Household members and those in childcare settings are at high risk

• Special attention to vulnerable groups such as infants under 6 months and pregnant women

Management

• Isolation: Advise immediate isolation of suspected cases in a single room with appropriate PPE for staff (surgical mask plus N95 where indicated)

• Supportive Care: Ensure adequate hydration and symptomatic treatment with antipyretics such as paracetamol

• Hospitalisation may be necessary for infants less than 6 months or patients with severe symptoms such as apnoea or pneumonia

Treatment

• First-line Antibiotic Therapy:

  • Azithromycin is preferred

    • Adults: 500 mg orally on day 1 followed by 250 mg daily for days 2–5

    • Children 6 months or older: 10 mg/kg (maximum 500 mg) on day 1, then 5 mg/kg (maximum 250 mg) daily for days 2–5

  • Alternatives include clarithromycin or trimethoprim-sulfamethoxazole for patients with contraindications

• Timing: Antibiotics are most effective in reducing transmission if given within 3 weeks of symptom onset, although they do not significantly alter the course of illness

Prophylaxis

• Indicated for all close contacts within 14 days of exposure regardless of immunisation status

• Use the same antibiotic regimen as treatment

• Emphasise vaccination for contacts, particularly for infants under 6 months, pregnant women in their final month, and partially immunised children

• For individuals aged over 10 years, administer a dTpa booster if more than 10 years have elapsed since the last vaccination

Investigations

• Diagnosis is primarily clinical but may be confirmed by:

  • Nasopharyngeal swab for PCR testing, most sensitive within 3 weeks of symptom onset using dacron or rayon-tipped swabs

  • Serology (IgM and IgG) if PCR is unavailable, noting that raised IgA indicates recent infection

• Routine laboratory tests are not required in uncomplicated cases

Prevention and Public Health Measures

• Pertussis is a notifiable disease; promptly report cases to public health authorities

• Advise exclusion from daycare or school until at least 5 days of antibiotic therapy are completed

• Vaccination is critical: the primary course is given at 2, 4 and 6 months, with a booster (dTpa) recommended at 15–17 years

• Special consideration for individuals born between 1966 and 1994, as they may have received only one dose of measles-containing vaccine and are at higher risk

• Maternal immunisation programmes are under investigation to provide early protection to newborns

Notes

• In older children and adults, pertussis may present as a persistent cough without the classic whoop

• Antibiotic treatment, while not altering the course of the illness, is essential to reduce infectivity and transmission

• Public health management includes contact tracing, isolation of exposed individuals and vaccination catch-up programmes

• Emphasise caregiver education regarding the signs of pertussis and the importance of timely medical review, particularly in outbreak settings

• Booster doses are necessary as immunity wanes within 4–12 years after the primary series

• In outbreak scenarios, update immunisation status and consider additional vaccination for high-risk groups to protect those too young to be immunised