Epidemiology of Infectious Diseases: Diphtheria
Corynebacterium diphtheriae of which there are two main forms, respiratory and cutaneous (affecting the skin).
C. diphtheriae has 3 biotypes - gravis, intermedius, and mitis. The most serious disease is associated with gravis but any strain may produce toxin.
Common clinical features
- Symptoms range from a moderately sore throat to toxic life-threatening diphtheria of the larynx or of the lower and upper respiratory tracts.
- Disease can involve almost any mucous membrane. For clinical purposes, it is convenient to classify diphtheria into a number of manifestations, depending on the site of disease1;
Anterior nasal diphtheria
Pharyngeal and tonsillar diphtheria
Cutaneous (skin) diphtheria.
- Cutaneous diphtheria is usually mild, typically consisting of sores or shallow ulcers and only rarely involving toxic complications.
- Endemic worldwide.
- A resurgence of diphtheria in the former Soviet Union occurred in the 1980s followed by a large epidemic from 1990. The epidemic spread throughout all the newly independent states, and peaked in 1994-5. Between 1990 and 1998, more than 157,000 cases and 5000 deaths were reported in the region4.
- Before the introduction of mass immunization in 1942 diphtheria was common in the UK with around 60,000 cases and 4,000 deaths reported each year2.
- In 2005 9 cases were notified in England and Wales.
- The overall case fatality rate is 5-10% with higher death rates (up to 20%) among children under 5 years old and adults aged over 40 years1.
Mode of transmission
Airborne droplets or direct contact with infected respiratory discharges or skin ulcers.
Period of Communicability
- Untreated cases remain infectious for up to 4 weeks, after 3 days of antibiotic treatment cases are no longer infectious.
- Rare chronic carriers may shed organism for 6 months or more1.
Prevention and control
Immunisation with diphtheria toxoid.
- National Immunization Program, Centers for Disease Control and Prevention, Epidemiology and Prevention of Vaccine-Preventable Disease 'The Pink Book', 9th edition, U.S. Department of Health and Human Services, 2006. Available at
- Heymann D L, editor, Control of Communicable Disease Manual. 18th ed. American Public Health Association, 2004.
- Health Protection Agency (HPA), Diphtheria fact sheet.
- Salisbury DM, Begg NT. Immunisation against infectious disease (The green Book). London: HMSO, 1996. Available at http://www.dh.gov.uk/assetRoot/04/07/29/84/04072984.pdf
© CM Kirwan 2006