Whoop, Whoop, Hooray

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Henry Goldstein wrote an excellent article on pertussis a few years ago.  With some interesting new data coming to press with regard to risk factors for complications of the disease we thought it might be worthwhile doing some spaced repetition.

“My childhood was full of deep sorrow – colic, whooping cough, dread of ghosts, hell, Satan, and a deity in the sky who was angry when I ate too much plum cake” – George Eliot

Although cases have been described as far back as the Middle Ages it wasn’t until 1906 when the organism, Bordetella pertussis, was isolated by Bordet and Gengou. Up to 16 million cases develop worldwide every year with the majority of cases being in the developing world. Australia reported around 10,000 cases in 2009. Data from 2013 suggests it caused at least 61,000 death worldwide though this is likely to be a gross underestimate. Pertussis is one of the leading causes of vaccine preventable deaths worldwide.

Incubation

B. pertussis is highly infectious with the majority of exposed household contacts becoming infected to various degrees. The incubation period is usually quoted as 4-21 days with the average being 7-10 days.

Prodrome

Before the harsh coughing begins there is often a couple of weeks of symptoms that could easily be mistaken for a viral upper respiratory tract infection. Children may have a runny nose and a very mild tickly cough. This is the catarrhal phase. The classic ‘whoop’ might not be hard until week three or four of the illness.

Clinical course

The classical presentation is of a patient that has paroxysms of coughing that terminates in an audible inspiratory ‘whoop’. Like most classical presentations we learn about in medicine this presentation is rarer than we think. Children may also present with a protracted cough, or forceful post-tussive vomiting. Parents often seek advice as their children have had a couple of courses of antibiotics with no improvement in cough. It’s not know as the ‘one hundred day cough’ for nothing.

People with pertussis (adults and children alike) are infectious from the beginning of the catarrhal stage through to the third week after the onset of the paroxysmal stage of coughing. They cease being infectious five days after a course of antibiotics.

Diagnosis

Other than a suspicious clinical picture, formal diagnosis is best made by performing PCR for Bordetella on a nasopharyngeal swab. Once the initial three weeks have past though, it becomes increasing difficult to culture and it may be necessary to use rising IgA titres to make the diagnosis though this does not affect management.

Treatment

A number of treatments have been posited including vitamin C injections.

“In 66 [of 81] cases… [we saw] reduction of lip cyanosis in coughing attacks…[disappearance of] attacks with breathing difficulty, vomiting and recurrence … also the number of cough attacks diminished. Patients became lively, had good appetite and the convalescence progressed very satisfactorily.” – Concerning the Vitamin C Therapy of Pertussis [Whooping Cough]: Otani, Klinische Wochenschrift, December 1936

Coughs last, on average, 16 days. A Cochrane review found no specific benefit of steroids, bronchodilators or immunoglobulins for the treatment of the cough. Over the counter remedies are unlikely to help and may potentially cause harm.  To hear more listen to this great rant from Dr Anthony Crocco. The only thing that may help (a little) is honey.  Take a listen to Ken Milne’s podcast SGEM #26 – Honey, Honey for more on this subject.

What about antibiotics? Well (in adults) they are recommended in the initial catarrhal phase to help reduce duration of infectivity but they don’t seem to have much effect after the disease has been hanging around for three weeks. Because of this they are not recommended beyond this time period.

If they are needed then macrolides such as erythromycin, azithromycin or clarithromycin are recommended. Azithromycin should be used in children less than one month of age as erythromycin use has been linked to an increased incidence of hypertrophic pyloric stenosis.

Complications

Pertussis is far from benign in unvaccinated infants. According to the CDC, in children under 1 that are not fully vaccinated:-

  • 1 in 4 (23%) get pneumonia
  • 1 in 100 (1.1%) will have convulsions
  • 3 out of 5 (61%) will have apneoic episodes
  • 1 in 300 (0.3%) will develop encephalopathy
  • 1 in 100 (1%) will die

In Winter’s retrospective analysis of US pertussis deaths in infants under 120 days old mortality was linked with:

  • Significantly low birth weight
  • Younger gestational age
  • Younger age at onset
  • Higher WBC and higher lymphocyte count

In those less severely affected it may still cause sub-conjuctival haemorrhages, rib fractures and loss of bladder control.

Post-exposure prophylaxis

So who should get antibiotics if exposed to a confirmed case of pertussis? Most guidelines recommend that the following groups of people receive antibiotic prophylaxis.  It’s not really to treat the illness but rather to halt the spread.

  • Pregnant mothers in the last month of gestation (WHY)
  • Members of a household that has an  infant that is not fully vaccinated
  • Healthcare workers and babies potentially exposed and in a newborn nursery environment

To be fully vaccinated the child must have three effective doses of pertussis vaccine given at least four weeks apart.

Prevention

Whilst childhood immunisation does prevent the majority of cases, individual immunity does appear to decrease with time so there has been an upswing in the number of older children and teenagers affected. Pertussis is a notifiable disease and over 70% of cases that are notified are in patients over the age of 15.

The current Australian immunisation schedule has pertussis vaccine being given as a part of the combined Diptheria, Tetanus, acellular Pertussis (DTaP) vaccine at two, four and six months of age. Other countries may have an alternative schedule. The child then receives a pre-school booster at 4 years old. Because of the waning immunity they should also receive a dose in their teenage years. An individual’s immunity to pertussis may well have disappeared by the time they reach adulthood so new parents, or grandparents living in a house with a newborn should be offered a booster.

 

HT to Tim Horeczko (@EMtogether) for the heads up regarding the latest data

 

References

Royal Children’s Hospital, Melbourne guidelines on Pertussis can be found here

Cherry JD. Historical review of pertussis and the classical vaccine. Journal of Infectious Diseases. 1996 Nov 1;174(Supplement 3):S259-63. full text here

Pertussis (Whooping cough) complications. (2015). Retrieved April 13, 2016, from http://www.cdc.gov/pertussis/about/complications.html

GBD 2013 Mortality and Causes of Death Collaborators. “Global, Regional, and National Age-Sex Specific All-Cause and Cause-Specific Mortality for 240 Causes of Death, 1990-2013: A Systematic Analysis for the Global Burden of Disease Study 2013.” Lancet 385.9963 (2015): 117–171. PMC. Web. 14 Apr. 2016.

Forsyth K, Plotkin S, Tan T, von König CH. Strategies to decrease pertussis transmission to infants. Pediatrics. 2015 Jun 1;135(6):e1475-82.

Hay AD, Wilson A, Fahey T, Peters TJ. The duration of acute cough in pre-school children presenting to primary care: a prospective cohort study. Family Practice. 2003 Dec 1;20(6):696-705

Winter K, Zipprich J, Harriman K, Murray EL, Gornbein J, Hammer SJ, Yeganeh N, Adachi K, Cherry JD. Risk factors associated with infant deaths from pertussis: a case-control study. Clinical Infectious Diseases. 2015 Oct 1;61(7):1099-106.

 

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An Emergency Physician with a special interest in education and lifelong learning. When not drinking coffee and reading Batman comics he is playing with his children.

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