Notification should occur when whooping cough is suspected on purely clinical grounds.
In infants (and particularly those ≤3 months) Bordetella pertussis causes a severe upper respiratory tract infection. In older children and adults it is milder, as is infection with Bordetella parapertussis.
Classic (severe) pertussis, as defined by the World Health Organization, consists of at least 21 days of cough illness with paroxysms, associated whoops or post-cough vomiting, and culture confirmation. Mild pertussis is any laboratory-confirmed pertussis disease that does not meet the criteria for classic disease.
B. pertussis is a small Gram-negative coccobacillus, which causes 300,000 deaths worldwide in children each year. In the UK, pertussis used to have its highest incidence in infants (school-aged children are often the source of infection for younger siblings) but now infection also occurs in adolescents and adults.
Pertussis is a cyclical disease with increases occurring every three to four years; the last peak occurred in 2008.
There has been a very large increase in laboratory-confirmed cases of pertussis in England and Wales in 2011 and 2012. The increase after the second quarter of 2011 was predominantly in adolescents and adults. This increase has continued in 2012 and extended into infants aged under 3 months, who are highest risk of severe complications, hospitalisation and death.
The provisional total of confirmed cases of pertussis in England and Wales to the end of July 2012 was 3,523, compared to 539 in the same period in 2008. Infection rates remain high in infants aged under 3 months, with 235 cases in this period in 2012 compared to 112 cases in 2008. Six pertussis-related deaths in infants were reported between 1 January and 31 July 2012 compared to five for the same period in 2008.
This increase in reporting may, in part, be due to increased awareness amongst health professionals but it is considered that the observed increases reflect a real change in pertussis activity.
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Note the vaccination history. The patient may be a child who is too young to have started the schedule. Children and adults can catch pertussis even if they were vaccinated in the past because both natural and vaccine immunity wane over time.
Pertussis commonly lasts for 6-8 weeks even when treated with antibiotics, with severity of symptoms related to age.
- The first stage is the catarrhal phase with symptoms of mild respiratory infection including sneezing, runny eyes and fever. This progresses after 1 or 2 weeks to the paroxysmal coughing stage.
- As the catarrhal symptoms wane, a dry, hacking cough starts, typically brought on by any sudden startle. Prolonged coughing episodes may be followed by the characteristic 'whoop'. The child chokes, gasps and flails the extremities, with eyes bulging and watering and face reddened. This is called the paroxysmal stage.
- The cough is very persistent, long after infection is past and may last for 2 or 3 months. It was called 'the 100 days' cough'.
- Infants especially are very unwell.
- The cough is impressive:
- If the child does not cough spontaneously, then touching the pharynx with a tongue depressor may trigger a spasm.
- The child will cough, cough, cough without drawing breath until the lungs are virtually emptied.
- A small child learns to follow this by breathing in through partially closed vocal cords and this causes the characteristic whoop.
- Older children and adults do not need to whoop and often do not do so. Infants may be unable to do so and may instead have apnoea and cyanosis after a paroxysm of coughing. Hence, the diagnostic feature is not so much the whoop as the persistent cough, cough, cough that empties the lungs before another breath can be drawn.
- The ferocity of the coughing may well cause vomiting. It can also produce subconjunctival haemorrhages. The child is often left exhausted.
Infectivity and incubation period
Incubation period is usually 7 to 10 days. It is most infectious in the catarrhal phase and can be considered non-infectious to non-household contacts three weeks after onset of paroxysms. This is reduced to five days if erythromycin or azithromycin is given.
Anyone who is diagnosed with whooping cough should stay off school/work until at least 21 days from the onset of symptoms or after taking antibiotics for at least five days (whichever is the sooner).
- Adenoviral infection - associated with fever, sore throat and conjunctivitis.
- Mycoplasma pneumoniae - usually a history of fever, headache and systemic symptoms at onset.
- Chlamydophila pneumoniae - commonly causes pharyngitis, bronchitis and atypical pneumonia, mainly in elderly and debilitated patients.
- Diagnosis can be confirmed by isolation of the B. pertussis organism through culture. However, culture lacks sensitivity and improved methods of diagnosis based on PCR and serological testing are available.
- B. pertussis can be isolated from the back of the nose using a pernasal swab:
- A pernasal swab is inserted through a nostril and advanced along the floor of the nose until it reaches the nasopharynx.
- It has been recommended that the swab be held against the posterior nasopharynx for up to 30 seconds but the patient can usually only tolerate the swab for a few seconds.
- Sampling of nasopharyngeal secretions in patients with whooping cough may precipitate a paroxysm of coughing and cause obstruction of the airways. Resuscitation equipment must therefore be available.
- Leukocytosis with absolute lymphocytosis occurs during the late catarrhal and paroxysmal phases and correlates with the severity of the disease. However, lymphocytosis is rare in adults, especially those who have been vaccinated.
- CXR: may show perihilar infiltrates or oedema with a variable degree of atelectasis. Secondary bacterial infection (or rarely, pertussis pneumonia) may cause consolidation.
Supportive therapy is the mainstay of treatment. This includes adequate fluid intake, adequate nutrition and oxygen therapy, including mechanical ventilation when required.
Hospital admission is particularly required for any infant aged under 6 months (unless there is only mild infection) and for any child with severe infection or underlying respiratory, cardiac or neuromuscular disease.
Although this is a bacterial disease, antibiotics do not alter the clinical course once the disease is established. However, erythromycin, clarithromycin or azithromycin may curtail the period of infectivity.
Antibiotics may also prevent or alleviate any secondary bacterial infection.
Severe complications and deaths occur mostly in infants aged under 6 months. Serious illness is less common in older children and adults.
- Severe complications in infants include pneumonia, encephalopathy and meningoencephalitis.
- Infants may experience weight loss, bronchitis, otitis media, apnoea, cyanosis, inguinal hernia and rectal prolapse.
- Problems in adults include fractured ribs, pneumothorax, inguinal hernia, aspiration pneumonia, seizures, otitis media and urinary incontinence.
The most severe infections are usually in infants, with morbidity and mortality greatest in those aged less than 6 months. About 50% of infants are admitted to hospital. Serious illness is much less common in older children and adults.
The cough can last for a long time and future upper respiratory tract infections may produce whooping for a while after.
See separate article Bordetella Pertussis (Whooping Cough) Vaccination.
Studies have shown that pregnant women mount a good immune response to pertussis vaccines, and this response should provide protection to neonates. Because of the increasing numbers of young infants becoming infected with whooping cough, the Chief Medical Officer has announced a temporary programme for pregnant women to be offered pertussis vaccination, with the programme starting in the first week of October 2012.
Close contacts of pertussis cases and those who are particularly vulnerable, unvaccinated, partially vaccinated or less than 5 years of age should be given erythromycin prophylaxis. Newer macrolide antibiotics such as azithromycin and clarithromycin are considered to be suitable alternatives.
Further reading & references
- Whooping Cough (Pertussis), Health Protection Agency
- Confirmed pertussis cases in England and Wales: update to end July 2012; Health Protection Report, Health Protection Agency, August 2012
- Guinto-Ocampo H et al, Pertussis, Medscape, Aug 2012
- Crowcroft NS, Pebody RG; Recent developments in pertussis.; Lancet. 2006 Jun 10;367(9526):1926-36.
- Greenberg DP, von Konig CH, Heininger U; Health burden of pertussis in infants and children; Pediatr Infect Dis J. 2005 May;24(5 Suppl):S39-43.
- Rothstein E, Edwards K; Health burden of pertussis in adolescents and adults; Pediatr Infect Dis J. 2005 May;24(5 Suppl):S44-7.
- Campbell H, Amirthalingam G, Andrews N, et al; Accelerating control of pertussis in England and Wales. Emerg Infect Dis. 2012 Jan;18(1):38-47. doi: 10.3201/eid1801.110784.
- Pregnant women to be offered whooping cough vaccination, Dept of Health, 28 September, 2012
|Original Author: Dr Hayley Willacy||Current Version: Dr Colin Tidy||Peer Reviewer: Dr Helen Huins|
|Last Checked: 09/10/2012||Document ID: 638 Version: 28||© EMIS|
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