Key learning points

  • Pertussis is a very infectious disease that usually comes in outbreaks but has had a higher than usual prevalence in the UK since the last outbreak in 2012
  • Babies under the age of six months with suspected pertussis should be admitted due to their relatively high mortality rate
  • Pertussis should be suspected if there is a cough for more than 14 days, which is paroxysmal with an inspiratory ‘whoop’ (often absent in babies), followed by vomiting. Babies may have apnoeic events
  • Diagnosis is via nasopharyngeal swabs available from public health, but sensitivity is low. Confirmed or suspected cases should be notified to public health
  • Pertussis can be prevented with the pertussis vaccine

Introduction

Pertussis, otherwise known as whooping cough, is an infectious disease caused by the bacterium Bordetella pertussis. It is probably underdiagnosed in the UK and is most common in infants and young children. In the last big outbreak, in 2012, the 17 UK deaths were all in unvaccinated babies under three months of age, therefore it is important to be particularly vigilant in this age group.1 

Case study

Freddie, a two-month-old baby, was brought to the surgery by his mother because he had been coughing for several weeks. It had started with a couple of weeks of him being ‘snotty’ and having conjunctivitis, which was treated with eye drops. He then developed a cough which came in fits – Freddie’s mother said that he had been waking at night having a coughing fit but would then go back to sleep. He would often vomit when coughing and she had been particularly worried the day before as his lips had turned blue and she thought that he had stopped breathing for a few seconds – she was going to call an ambulance when he started breathing and returned to a normal colour. Freddie is due to have his first immunisations next week – his mother delayed the appointment because he had been ill. You could not find much on examination. Freddie’s chest was clear and his observations were normal, and he did not cough while in the room with you. 

Freddie’s outcome

You were concerned by the report of cyanosis and apnoea, so referred Freddie to the on-call paediatricians, who later wrote to say that pertussis had been diagnosed and Freddie was admitted. 

Discussion 

Pertussis can be difficult to diagnose, but NICE recommends that the following clinical features should spark suspicion of pertussis in those with an unexplained cough for two weeks or more:1

  • Paroxysmal cough and inspiratory whoop – the cough comes in an expiratory burst, then an inspiratory gasp which causes the typical ‘whoop’ sound, though this is often absent in infants
  • Vomiting after the cough 
  • Undiagnosed apnoea in infants.

There is a two-week prodrome where the patient has a catarrhal illness, with a temperature, conjunctivitis, malaise and a dry cough. Suspicion should be raised if the patient has been in contact with someone with pertussis or attends a school or nursery where there is a known outbreak. The last big outbreak was in 2012 and outbreaks usually happen every three to four years so it is important to be on the lookout for cases. Prevalence has remained higher since 2012 than is usually the case between outbreaks. The vaccination programme for pregnant women, which was introduced during the 2012 outbreak, is due to be reviewed later in 2019.1,2

Anyone aged under six months, or who is systemically unwell or has a complication such as seizures or pneumonia should be admitted. If not admitting, a macrolide is the appropriate treatment if the patient presents within three weeks of onset. Azithromycin or clarithromycin should be the first choice, with the exception of pregnant women who should be prescribed erythromycin. Antibiotics are only likely to improve the patient’s symptoms if given within the first three weeks, but after this they should be given to help reduce onward transmission. Pertussis is also known as the ‘100 day cough’ so patients, particularly those treated after three weeks, should be advised to expect the cough to continue for three months or so.1 

The diagnosis should be confirmed, usually by nasopharyngeal swabs, which can be obtained from the local public health department. However, these are not 100% sensitive and sensitivity decreases with time from onset of symptoms. A negative swab therefore does not rule out pertussis.1,2 Suspected or confirmed pertussis should be notified to public health.3

Prevention

Pertussis can be prevented with the pertussis vaccine, which forms part of the 6-in-1 vaccine given as part of the UK immunisation schedule at 8, 12 and 16 weeks old. A booster is also included in the 4-in-1 pre-school booster vaccine.4

In addition, all pregnant women should receive the pertussis vaccine during pregnancy to protect both the mother and the newborn.4

Summary

Pertussis is a serious condition, particularly in those under the age of six months in whom mortality is 3.5% and for whom death can be sudden and unexpected.1 We should all continue to promote vaccination to try and reduce the spread of pertussis and should be on alert for the next large outbreak.

Dr Toni Hazell is a GP in London

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