Epidemiology of Infectious Diseases: Pertussis (Whooping Cough)
An acute bacterial respiratory infection caused by Bordetella pertussis.
Common clinical features
- Characterized by 3 stages;
- The catarrhal stage - onset of coryza, sneezing, low-grade fever, and a mild cough (1-2 weeks), followed by the paroxysmal stage - bouts of coughing ending with a high-pitched inspiratory whoop or vomiting (lasting 1-6 weeks but may persist for up to 10 weeks).
- During the convalescence stage recovery is gradual and the cough becomes less paroxysmal and disappears in 2-3 weeks (recovery may take weeks to months).
- The most severe infections are in infants of which over 50% are hospitalized (HPA).
- In adults symptoms range from mild respiratory infection to paroxysmal cough episodes.
- Complications include, pneumonia, seizure, encephalopathy, weight loss and death.
- Complications are most likely to occur in young infants among who the most common cause of pertussis related deaths is secondary bacterial pneumonia.
- Pertussis can occur in previously immunized and infected individuals, but immunization and prior infection attenuate the clinical picture.
- Endemic worldwide.
- Pertussis is a major cause of childhood morbidity and mortality in developing countries, where an estimated 50 million cases and 300,000 deaths occur each year.
- In the UK notifications have declined significantly since the introduction of pertussis immunization with 594 cases reported in 2005.
Mode of transmission
Droplet spread from an infectious case.
Average 9-10 days with a range of 6-20 days.
Period of Communicability
Persons with pertussis are highly infectious during the catarrhal stage and during the first 2 weeks of the paroxysmal stage. A case is normally not infectious 3 weeks after the onset of the paroxysmal stage, though in up to 20% of cases infectivity may persist for up to 6 weeks2.
When treated with erythromycin patients are no longer contagious after 5 days of treatment1.
Prevention and control
- Maintain high immunization coverage
- In the UK accellular pertussis vaccine is given in the primary course with diphtheria, tetanus, polio and Hib (as DtaP/IPV/Hib), given at aged 2,3, & 4 months of age. A further booster dose is given with the preschool boosters between the ages of 3 and 5 (Health Protection Agency).
- Respiratory isolation for cases until at least 5 days (or until 14 day course of erythromycin completed).
- Arrange for laboratory confirmation2.
- Vaccination of unvaccinated household contacts and exclusion from school etc.
- Antibiotic prophylaxis may be of value for unvaccinated household contacts of cases, particularly in infants <6 months of age, if given within 21 days of onset of the first case2.
- Heymann D L, editor, Control of Communicable Disease Manual. 18th ed. American Public Health Association; 2004.
- Hawker J, Begg N, Blair I, Reintjes R, Weinberg J. Communicable Disease Control Handbook, Blackwell, 2005.
© CM Kirwan 2006