pertussis (whooping cough)

see also The child with a cough, clinically important bacteria, antibiotics, bronchiectasis, the persistent cough

• RCH guideline - pertussis
• Australian Prescriber April 2009 - Managing pertussis in adults plus antibiotic prophylaxis for high risk contacts
• Pertussis Information for GPs and other Health Care Providers on Clinical and Public Health Management (Western Australia - March 2010)

• pertussis is caused by a bacteria Bordetella pertussis
• it is extremely infectious and not only causes 10-30% of all subacute coughs, but can be fatal in high risk patients such as infants
• vaccination is partly protective but very important in reducing spread, all children should be vaccinated unless there are C/I, and likewise adolescents and adults should have a booster as immunity wanes by 10yrs

• the number of cases rose in 2024–25 to the highest level recorded in Australia in 35 years - over 57,000 cases were identified in 2024 (26,000 in NSW and over 15,000 in Qld - rates double that of the other states), including 37,663 that affected infants and children aged up to 14 with rising to almost 800 cases per 100,000 Australian children in 2024–25, up from average annual 184 per 100,000 children for the pre-pandemic years 2015-2019. The last peak was in 2011 when nearly 39,000 cases were recorded and 2010 when 30,000 cases were recorded compared to an average from 1991-2007 of under 6000 cases per year. Childhood vaccination rates had peaked in 2020 but since then have gradually fallen. ¹⁾

• incubation period is typically 7–10 days (range of 4–21 days)

• the symptoms are similar to coryza / the common cold / viral rhinopharyngitis / rhinitis

• after 1-2 weeks, a paraoxysmal dry cough develops which can last months, and in children, often develops the classical whooping cough, or may just have post-tussive vomiting or syncope
• FBE may show lymphocytosis

• diagnosis is often clinical by the time the paroxysmal stage develops, and unfortunately, little can be done at this time as after 3wks of illness, starting antibiotics will have little benefit
  • after the 1st 3wks, consider pertussis serology to diagnosis cases of subacute cough:
    • “pertussis-specific IgA is only produced after natural infection, whereas IgG rises with vaccination and natural infection. While a positive IgA test confirms the diagnosis of pertussis, a negative result does not exclude the possibility of infection. (It is important to remember that a small proportion of the population has an IgA deficiency.) Paired samples showing rising titres of specific IgA or IgG are a more reliable indication that the patient has pertussis.”
• those in contact with known cases of pertussis or contacts with subacute coughs, should be considered for nasopharyngeal swab for PCR (BEFORE antibiotics) and empirical antibiotics in the catarrhal stage to reduce infectivity
  • this is particularly important for healthcare workers, last trimester pregnancy, contacts with children under 2yrs who are not fully vaccinated, such as child care workers

• close contacts
  • consider antibiotic prophylaxis of close contacts, particularly if there are un-immunised infants at risk
• if in 1st 2wks:
  • nasopharyngeal swab for PCR, preferably before starting antibiotics
  • empirical antibiotics²⁾:
    • azithromycin 10mg/kg (up to 500mg) daily for 3 days, or,
    • azithromycin 10mg/kg (up to 500mg) day 1, then 5mg/kg (up to 250mg) daily for next 4 days, or,
    • clarithromycin bd for 7 days, or,
    • co-trimoxazole bd for 7 days if the above are not tolerated
  • patients should avoid contact with susceptible individuals until at least five days of antibiotics have been taken
• if after 3rd week:
  • antibiotics, steroids, asthma Rx, antihistamines are of NO benefit (unless patient also has asthma in which case asthma Rx should be continued if one believes the symptoms are asthmatic and not pertussis cough)
  • if Dx is not clear, consider pertussis serology as outlined in Dx section