How to deal with suspected whooping cough cases

GP Dr Toni Hazell explains the background to the current wave of whooping cough and how GPs should identify and manage cases of this serious infection

I’m always impressed when prospective medical students cite interventions with population-wide benefits – such as antibiotics, insulin and vaccinations – when asked to describe the most impactful medical therapy advances in the last century (rather than high-tech innovations like stem cell therapy that have so far benefited a relatively small number of people).

Unfortunately we are currently seeing some of these gains go into reverse – as we have seen in particular with falls in vaccination coverage and the alarming resurgence of measles. Another worrying consequence of this is the current wave of cases of whooping cough, the clinical manifestation of infection with Bordetella pertussis.

There were over 100,000 cases of whooping cough per year in England and Wales prior to the introduction of vaccination in the 1950s, and it wasn’t uncommon to see over 2,000 deaths per year; even now, 1% of infants aged less than two months who contract whooping cough will die.

The current anti-vaxx movement is very much driven by social media, but it existed in a lesser form before the smartphone was even a twinkle in Steve Jobs’ eye. I was one of the generation of babies who didn’t have my pertussis vaccine at the usual time, due to unfounded concerns about brain damage as an adverse effect; happily I didn’t contract the disease during the outbreaks in the late 1970s and early 1980s, which were caused by reduced vaccination levels.

Uptake fell from 79% in 1973 to a low of 31% in 1978, recovering by the early 1990s. Sadly we seem to have learnt little in the intervening decades – 2022 uptake of the newborn pertussis vaccine in England was 62%, with rates in London being much lower at 41%. The most recent figures available show that uptake of the vaccine given in pregnancy has also fallen to 61% in 2022/23, a decrease of 4% from the year before and 7% from the year before that. This is particularly concerning, as immunity wanes over time and pregnant women who no longer have immunity from their newborn vaccines (or who were never vaccinated as a child) cannot pass antibodies through the placenta to protect their newborns before they themselves are vaccinated. It is unsurprising therefore that whooping cough is on the increase; there were 1,737 notifications in England and Wales in 2023, a trebling from the 553 cases in 2022.

Clinical features – what to look for

So, how can we recognise those with pertussis and differentiate them from the much larger group with a non-specific respiratory viral infection? Patients with pertussis will have two separate clinical phases. For an average of 7-10 days they have what looks like a cold, with a runny nose, mild cough, sore throat and conjunctivitis. This then evolves into a cough which is qualitatively different – it comes in fits, which are impossible to control and often happen at night. The name whooping cough comes from the fact that the cough has a short expiratory phase and then an inspiratory gasping action, which can cause a ‘whoop’ sound, shown on this video.

Patients feel very unwell – they may vomit whilst coughing, adults feel sweaty and may occasionally black out, children can become cyanosed. There is not usually a high fever. This cough lasts for up to 10 weeks and there is then a convalescent phase for 2-3 weeks. We should therefore suspect pertussis in anyone who appears to have had that clinical course, with an apparent cold that then develops into an uncontrollable cough, particularly if associated with a whooping sound or with vomiting.

Confirming diagnosis

Whooping cough is notifiable when suspected – in some areas the notification may prompt public health to send out a swab, in others this has to be done separately. The exact testing arranged by public health will vary with age and duration of symptoms (see box 1) – if the cough has been present for up to three weeks then culture (from eg, nasopharyngeal swab or aspirate, or per nasal swab) is suitable. Antibody testing may be used later in the infection.

How to distinguish from other causes of cough

The differential diagnosis of pertussis includes other infectious causes of coughing, both viral and bacterial, as well as non-infectious causes, which will be more or less likely depending on the age of the patient. These include asthma and COPD, reflux, a cough which lingers after a viral infection, and malignancy. We should be aware that the ‘whoop’ is less pronounced in children, and so its absence should not prevent us thinking about whooping cough, and also that those who have previous vaccination or have previously had whooping cough may present with less severe symptoms.

Management

Treatment of pertussis is with a macrolide antibiotic and is generally only useful within the first 21 days of the cough. If a patient presents later than that, supportive care similar to that for any respiratory infection is the only management. Confirmation by public health may take longer than 21 days and so if there is a clinical suspicion strong enough to arrange a swab, it would be sensible to treat. The cough will usually take weeks to resolve, even with treatment and it is for this reason that it has acquired the nickname ‘the 100-day cough’ – treatment does however reduce the duration down to a few weeks from a few months.

When assessing any acutely ill patient we always consider whether they need admission and this should be arranged if there are any serious complications (complications are listed in box 2) or if there is cyanosis or episodes of apnoea. We should have a low threshold for same-day referral in children aged under six months, due to the high mortality rate. Children aged under three months with suspected pertussis are always admitted. If a patient is being sent in to your local hospital, make sure that they are aware of the suspected diagnosis so that appropriate precautions can be taken to reduce onward transmission.

Prevention measures

Any unvaccinated patient who develops pertussis should still be offered vaccination after they have recovered – pregnant women are vaccinated ideally between 16 and 32 weeks of pregnancy, but up to 38 weeks if necessary. High-risk close contacts (listed in box 3) may be offered prophylaxis – unless you have an enhanced service, it is contractually the job of public health rather than primary care to organise this, including provision of prescriptions.

Prophylaxis is offered to close contacts of an index who is less than 21 days from the start of their symptoms – everyone who is offered prophylaxis should also be offered vaccination.

Children should stay off school for 48 hours after the start of antibiotic treatment, or 21 days from the start of symptoms of not treated – the same advice is given for those who work in a healthcare setting. Those in other settings should avoid contact with infants under one year who are not fully vaccinated, for the same length of time.

Like measles, pertussis used to be endemic, but the success of vaccination means that many healthcare professionals will never have seen a case. It is important that we are aware of how it presents and have a low threshold for suspicion of the condition and to arrange notification and testing, as well as promoting vaccination to parents of newborns and pregnant women.