Whooping Cough

Original Author: Sam Romaine and Dr Razi Paracha
Last Updated: 18th August 2018
Revisions: 46

Whooping cough is a highly infectious notifiable disease caused by the bacterium Bordetella Pertussis. This article will discuss the epidemiology, pathophysiology, clinical features, diagnosis, management and complications of pertussis.



Epidemiology

Before a vaccine was introduced in the 1950’s around 120,000 cases occurred annually in England and Wales (1), compared to 4457 laboratory confirmed cases in 2015 (2,3). Classically pertussis was a highly infectious disease of infants, particularly those under 3 months of age whom were yet to be vaccinated.

However, since 2006 incidence has risen rapidly in older children and adults, with the overwhelming majority of cases now occurring in those aged 15 and over (2,3). This increase in cases diagnosed in older children and adults is likely due to the introduction of improved diagnostic tests rather than a true rise in incidence (4).

Despite this increase, cases in older children and adults tend to be much milder, whilst infants remain most at risk of hospitalisation and death due to pertussis (5). The incidence of pertussis tends to peak every 3-4 years for reasons that are poorly understood (1). The last peak was in 2012 in which 9710 laboratory confirmed cases occurred in England and Wales (2,3).



Vaccination

Vaccines against pertussis are given at 2, 3 and 4 months of age, with a booster at 3 years and 4 months (6). Immunity granted by the vaccination wanes after 5 to 10 years but infection is much milder in adolescents and adults (7).

In 2012 a temporary program of vaccination of pregnant women was introduced in the UK, with the aim of conferring passive immunity in the first few months of life (to offer protection before vaccination) through the transfer of maternal antibodies in-utero (5). This program was extended in 2014 for at least another 5 years after it was found to be safe and effective (5).



Pathophysiology

Bordetella Pertussis is a gram-negative bacillus which spreads through aerosolised droplets produced by the cough of an infected individual. The bacteria attach to the respiratory epithelium and produce toxins which paralyse the cilia and promote inflammation, impairing the clearance of respiratory secretions, which leads to a cough (8).

Bordetella Pertussis is highly contagious, with up to 90% of household contacts developing the disease (9).


Risk factors

The primary risk factors for pertussis are non-vaccination and exposure to an infected individual (especially during the catarrhal phase) (8).


Clinical features

Whooping cough typically progresses through three stages. The first phase, the catarrhal phase, lasts 1 to 2 weeks and produces symptoms including:

  • Rhinitis
  • Conjunctivitis
  • Irritability
  • Sore throat
  • Low-grade fever
  • Dry cough

As these symptoms mimic other upper respiratory tract infections, pertussis is rarely diagnosed at this stage unless there has been contact with an individual known to be infected.

The paroxysmal phase occurs next. It typically lasts for 2-8 weeks and is the time when complications frequently occur. This phase is characterised by episodes of severe paroxysms of coughing followed by an inspiratory gasp, producing the classic “whoop” sound.

Mayo clinic video of whooping cough (10)

 

 

 

 

In infants below 3 months of age, the “whoop” is less common and apnoea is more often a feature. These paroxysms of coughing are more common at night, are often followed by vomiting and may be severe enough to cause cyanosis.

Finally, the cough gradually decreases in frequency and severity during the convalescent phase, which may last up to 3 months (1).

In uncomplicated pertussis there is often little to find on examination. There is sometimes a low grade fever. Conjunctival haemorrhages and facial petechiae may be present due to vigorous coughing, however chest auscultation is usually normal (11).



Differential diagnoses

The main differential diagnoses to consider in a child presenting with a paroxysmal cough are listed below, with key features that increase the likelihood of each diagnosis in bullet points beneath (12).

Bronchiolitis/viral respiratory infection

  • Wheeze and / or crackles (absent in pertussis)
  • Age under 1 year
  • Acute history

Mycoplasma pneumonia

  • Chest signs: Wheeze and / or crackles (absent in pertussis)
  • No lymphocytosis and usually a normal white cell count
  • Nasopharyngeal PCR confirmation

Bacterial pneumonia

  • Chest signs: Focal crackles
  • High temperature

Asthma

  • Chronic night time cough, or exercise-induced cough
  • Recurrent episodes of breathlessness or wheeze (absent in pertussis)
  • Personal or family history of atopy, eg. eczema, hayfever or asthma

Tuberculosis

  • Chronic cough
  • Growth failure / weight loss (absent in pertussis)
  • History of contact with an individual with TB, or travel to a TB endemic country

Investigations

Investigations used to diagnose pertussis differ depending on the patient’s age, duration of symptoms, and local laboratory facilities. If the cough is less than 2 weeks in duration, a culture of a nasopharyngeal aspirate or nasopharyngeal swab is recommended. PCR testing of a nasopharyngeal swab may also be done in severe illness as results are available sooner than with cultures.

If the cough is greater than 2 weeks in duration anti-pertussis toxin IgG serology is recommended in children under 5, whereas anti-pertussis toxin detection in oral fluid is recommended in children aged 5-17. A limitation of both serology and oral fluid testing is that a pertussis vaccine within the last year can produce a false positive (1).

FBC usually reveals a lymphocytosis (+/- elevated white cell count).


Management

Hospital admission is indicated for those:

  • Who are under 6 months of age and acutely unwell
  • With significant breathing difficulties, e.g. apnoeic episodes, cyanosis, respiratory distress or severe paroxysms of coughing
  • Feeding difficulties
  • With significant complications, e.g. pneumonia or seizures

Antibiotics do not alter the clinical course once the disease is established, however they may reduce the period of infectivity when given early on in the course of the illness. A macrolide antibiotic should be prescribed when the duration of the cough is less than 21 days:

  • Clarithromycin for those under 1 month, azithromycin or clarithromycin for those over 1 month
  • Co-trimoxazole is the 2nd line antibiotic where macrolides are contra-indicated or poorly tolerated

Further management is supportive, including paracetamol and / or ibuprofen for symptomatic relief and adequate fluid intake to prevent dehydration.

Parents should be notified that despite antibiotic treatment the cough may take up to 3 months to resolve. In addition, parents should be made aware of the symptoms of possible complications and to seek medical help if these develop. The child should avoid nursery or school until they have had the cough for 21 days or have had antibiotics for 5 days (1).


Complications

More serious complications include:

  • Secondary bacterial pneumonia (up to 20% of infants)
  • Seizures
  • Encephalopathy (rare)

 

Less serious complications include:

  • Otitis media

Complications and a poor prognosis are most likely in unvaccinated young infants, with a mortality rate of 3.5% in children under 6 months of age compared to 0.03% in those over 6 months. In those with some immunity (vaccination or previous pertussis infection) the disease is usually mild and serious complications are very rare (1).


References

(1) NICE Clinical Knowledge Summaries. Whooping cough. 2015; Available at: http://cks.nice.org.uk/whooping-cough. Accessed 09/19, 2016.
(2) Public Health England. Laboratory confirmed cases of Pertussis infection by age group, England: 1994 to 2015. 2016; Available at: https://www.gov.uk/. Accessed 09/19, 2016.
(3) Public Health Wales. Pertussis (Whooping cough). 2016; Available at: http://www.wales.nhs.uk/sites3/page.cfm?orgid=457&pid=58100#data. Accessed 09/19, 2016.
(4) Campbell H, Amirthalingam G, Andrews N, Fry NK, George RC, Harrison TG, et al. Accelerating control of pertussis in England and Wales. Emerging Infectious Diseases 2012 Jan;18(1):38-47.
(5) Patient UK. Whooping cough. 2015; Available at: http://patient.info/doctor/whooping-cough-pro. Accessed 09/19, 2016.
(6) NHS Choices. When to have vaccinations. 2016; Available at: http://www.nhs.uk/conditions/vaccinations/pages/vaccination-schedule-age-checklist.aspx. Accessed 09/19, 2016.
(7) Duration of effectiveness of pertussis vaccine: evidence from a 10 year community study. Jenkinson D. Br Med J (Clin Res Ed). 1988;296(6622):612.
(8) Medscape. Pertussis: Practice Essentials, Background, Etiology and Pathophysiology. 2016; Available at: http://emedicine.medscape.com/article/967268-overview#a4. Accessed 09/19, 2016.
(9) Public Health England. Guidelines for the Public Health Management of Pertussis in England. 2016; Available at: https://www.gov.uk/ Accessed 09/19, 2016.
(10) Mayo Clinic video of whoop. https://youtu.be/S3oZrMGDMMw
(11) Medscape. Pertussis: Clinical Presentation, History, Physical Examination. 2016; Available at: http://emedicine.medscape.com/article/967268-clinical#b3. Accessed 09/19, 2016.
(12) World Health Organisation. Pocket Book of Hospital Care of Children: Cough or difficulty breathing. 2013; Available at: http://www.ncbi.nlm.nih.gov/books/NBK154448/. Accessed 09/19, 2016.

Authors:

1st Author: Trainee doctor Sam Romaine

Senior review: Dr Razi Paracha, Paediatric ST5

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