Bugs – Pertussis / Whooping cough

Mode Of Infection

Pertussis (Whooping cough) is caused by the bacterium, Bordetella pertussis. It is highly contagious, easily transmitted from person-t- person by droplets.

It occurs mainly in infants and young children, but recent years has seen an upsurge in adult infection, due to vaccine programme gaps and waning immunity.

Symptoms

First symptoms commence 7–10 days after exposure to an infected person. This infected person may be asymptomatic or have mild, non-specific symptoms that include mild fever, runny nose and cough. In classical cases the cough develops into a paroxysmal cough followed by whooping (hence the common name of whooping cough).

Very young babies may stop breathing after prolonged bouts of coughing. Pneumonia is a common complication and in some instances the patient may lose consciousness or have a fit.

Adults seldom develop the typical ‘whoop’ but may continue coughing for weeks. Thus it is referred to as ”The Hundred Day Cough”

Geographical Distribution

Pertussis occurs all over the world but may be more common in the developing world as vaccine coverage is poor. The developed world is seeing an increasing number of cases due to a number of factors not least of all complacency amongst the general public. This leads to dropping immunization cover. In South Africa there are always cases in the community, most of which go undiagnosed but act as a source of infection for others.

Transmission

The bacteria is transmitted between individuals by infected respiratory droplets. It is most contagious before the typical cough starts. New-born babies are at high risk of severe disease and may contract the disease from un-immunised adults or adults who have lost their immunity. Hence the importance of vaccinating teenagers and adults again at 10 yearly intervals.

Treatment

Antibiotics may be effective but only in the first week or two when the disease is often not yet formally recognized. Antibiotic treatment does not necessarily shorten the period of coughing.

Prevention

Universal infant vaccine coverage of more than 90% is necessary to effectively stem transmission. The WHO estimates that global cover is little more than 80% and less so in developing countries including South Africa.

Vaccination

The vaccine is included in the Childhood Immunisation Programme in South Africa but infants may be infected by siblings, parents and grandparents who had either not been vaccinated or have lost their immunity. Therefor all persons should receive a booster every ten years. The vaccine is included in a very cost-effective vaccine that also provides protection against tetanus and diphtheria.

The vaccine is given to babies as a primary series that forms part of the core of the Expanded Programme of Immunisation (EPI) of the WHO. The vaccine is given at 6, 10 and 14 weeks and a final childhood booster at 18 months. Teenagers should receive a booster at 12 years and so should all pregnant women. All adults should receive a single booster once in adulthood to ensure adequate protection.