Travellers

Travel Health Information Sheets

Diphtheria                               

Introduction

Diphtheria is a bacterial disease caused by Corynebacterium diphtheriae, an aerobic, gram-positive, pleomorphic bacillus.  C. diphtheriae can be infected by a bacteriophage carrying genes for diphtheria exotoxin; this toxin is responsible for the disease manifestations. The toxin inhibits cellular protein synthesis causing local tissue destruction and when it is systemically absorbed can lead to myocarditis and neuritis [1]. 

The major clinical manifestations are laryngeal/pharyngeal diphtheria (with the name diphtheria coming from the ‘leathery’ membrane in the pharynx), cutaneous ulceration, and systemic toxicity. Humans are the only natural hosts of diphtheria [2, 3].

Epidemiology (to be added soon)

(Data from the Travel and Migrant Health Section of the Health Protection Agency Centre for Infections)

Risks for Travellers

A widespread and effective vaccination programme has made diphtheria rare in resource-rich countries of the Western hemisphere.  Cases of diphtheria occasionally occur in unvaccinated travellers to endemic regions (see Global Epidemiology), and those travelling to these regions (especially those spending prolonged periods with the local population) must ensure they are vaccinated.

Transmission

Diphtheria is spread between humans via respiratory droplets and occasionally through contaminated fomites or from exudates from infected skin lesions. Conditions of crowding and poor hygiene increase the risk of transmission. Chronic carriage and asymptomatic infections are common [3].

 

Signs and symptoms [1-3]

The incubation period is between 2 and 7 days.  The symptoms may be classified as local or systemic, depending upon whether there has been spread of the exotoxin. 

Respiratory tract diphtheria

There are several, often overlapping syndromes associated with respiratory tract diphtheria.  The most common is pharyngeal diphtheria affecting the soft palate, tonsils and pharyngeal area.  A tough grey/yellow membrane is formed and is firmly attached to the underlying tissue.  The lymph glands become swollen, prominent and tender producing a ‘bull neck’.

Infection may spread to the larynx leading to laryngeal diphtheria.  As a result there will be a husky voice, a brassy cough and if there is airway obstruction, dyspnoea and cyanosis.

Nasal diphtheria is associated localised infection of the anterior nares usually with a low grade fever, a nasal discharge, and crusting and erosion on the external nares.

Systemic spread of the exotoxin can lead to toxic effects primarily on the cardiac and neurologic systems.

Cardiac toxicity occurs in 10% to 25% of persons with respiratory diphtheria, usually manifesting after one to two weeks of disease. Myocarditis is associated with electrocardiographic changes, dyspnea, weakness, congestive heart failure and circulatory collapse.

Neurological complications can present as palatal and pharyngeal wall paralysis early in the course of the disease, or after several weeks, as cranial nerve palsies, paraesthesias, polyneuropathy and rarely encephalitis. Approximately 5% - 10% of respiratory cases are fatal.

Cutaneous diphtheria presents as a chronic non-healing ulcer usually co-infected with staphylococci and streptococci. It has typically been seen in the tropics, although cases have been described in western settings among homeless populations [1].  Clinical findings can either be that of a punched out ulcer with non-distinct margins, covered with a grey/white to brown membrane, or a chronic non-specific rash. Systemic complications and fatalities are rare with this form. Most of the recent cases in travellers who have returned to the UK have been of cutaneous diphtheria [4].

Treatment [1, 3]

Treatment of diphtheria requires both anti-toxin to neutralise the diphtheria exotoxin, and antibiotics to eradicate and prevent carriage of the bacteria. Antitoxin should be administered early in the course to prevent disease progression. As the antitoxin is an equine product, anaphylaxis and serum sickness can occur, and patients should be skin-tested before administration.

Antibiotic treatment is usually with penicillins or macrolides. Intensive care is required in serious cases.

Prevention

The most important method for prevention of diphtheria is vaccination. Maintaining high vaccination levels in a population will lead to herd immunity and decreased circulation of the bacteria and risk of disease. Improved sanitation and personal hygiene, as well as decreased population crowding will also lessen conditions leading to transmission of the bacteria.

It is important to maintain lifelong immunity. In the UK, school leavers receive a diphtheria/tetanus/polio booster in order to maintain high levels of immunity [5]. See Vaccination Information.

Contacts of cases should be traced, screened for infection by throat culture, and treated as necessary. They should also receive a booster dose of diphtheria toxoid.

References

1. MacGregor RR. Corynebacterium diphtheriae. In: Mandell GL, Bennett JE and Dolin R, eds. Principles and Practice of Infectious Diseases. 6th ed. Philadelphia: Churchill Livingston, 2005:2457-2465.

2. Centers for Disease Control.   Diphtheria. In: National Immunization Program Pink Book. Atlanta: CDC; 8th ed. 30 January 2004

http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/dip.pdf

3. Kumar P, Clark M.  Clinical Medicine 5th ed. Edinburgh: WB Saunders Co Ltd; 2002  www.kumarandclark.com

4. Health Protection Agency. Diphtheria in England and Wales: 2001 to 2004. Commun Dis Rep Weekly (serial online) 2005;15:7-10

5. Diphtheria. Draft chapter for revised version of: Immunisation Against Infectious Disease. 2005 Available at http://www.dh.gov.uk/prod_consum_dh/ groups/dh_digitalassets/ @dh/@en/documents/digitalasset/dh_4123229.pdf

 

Reading List

Cook G, Zumla A, ed.  Manson’s Tropical Diseases. 21st ed. London: WB Saunders Co Ltd; 2003

Plotkin S, Orenstein W, editors. Vaccines 4th Edition. Philadelphia: WB Saunders Co Ltd; 2004

Links

World Health Organization http://www.who.int/health_topics/diphtheria/en

Committee to Advise on Tropical Medicine and Travel (CATMAT) http://www.phac-aspc.gc.ca/im/vpd-mev/diphtheria_e.html