Diphtheria once was a major cause of illness and death among children. The U.S. recorded 206,000 cases of diphtheria in 1921, resulting in 15,520 deaths. Starting in the 1920s, diphtheria rates dropped quickly in the U.S. and other countries that began widely vaccinating. Between 2004 and 2008, no cases of diphtheria were recorded in the U.S. However, the disease continues to play a role globally. In 2011, 4,887 cases of diphtheria were reported worldwide to the World Health Organization (WHO), but many more cases likely go unreported.
The case-fatality rate for diphtheria has changed very little during the last 50 years. The overall case-fatality rate for diphtheria is 5%–10%, with higher death rates (up to 20%) among persons younger than 5 and older than 40 years of age. Before there was treatment for diphtheria, the disease was fatal in up to half of cases.
The incubation period of diphtheria is 2–5 days (range, 1–10 days). Diphtheria 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 disease:
- Respiratory diphtheria
- Anterior nasal diphtheria
- Pharyngeal and tonsillar diphtheria
- Laryngeal diphtheria
- Cutaneous diphtheria
After the provisional clinical diagnosis is made and appropriate cultures are obtained, persons with suspected diphtheria should be given antitoxin and antibiotics in adequate dosage and placed in isolation. Respiratory support and airway maintenance should also be administered as needed. In the United States, diphtheria antitoxin can be obtained from CDC on request.
Treatment with erythromycin orally or by injection (40 mg/kg/day; maximum, 2 gm/day) for 14 days, or procaine penicillin G daily, intramuscularly (300,000 U/day for those weighing 10 kg or less, and 600,000 U/day for those weighing more than 10 kg) for 14 days. The disease is usually not contagious 48 hours after antibiotics are instituted. Elimination of the organism should be documented by two consecutive negative cultures after therapy is completed.
For close contacts, especially household contacts, a diphtheria toxoid booster, appropriate for age, should be given. Contacts should also receive antibiotics—benzathine penicillin G (600,000 units for persons younger than 6 years old and 1,200,000 units for those 6 years old and older) or a 7- to 10-day course of oral erythromycin, (40 mg/kg/day for children and 1 g/day for adults). For compliance reasons, if surveillance of contacts cannot be maintained, they should receive benzathine penicillin G. Identified carriers in the community should also receive antibiotics. Contacts should be closely monitored and antitoxin given at the first sign(s) of illness.
Contacts of cutaneous diphtheria should be treated as described above; however, if the strain is shown to be nontoxigenic, investigation of contacts can be discontinued.
Circulation appears to continue in some settings even in populations with more than 80% childhood immunization rates. An asymptomatic carrier state can exist even among immune individuals.
Immunity wanes over time and a booster dose of vaccine should be administered every 10 year to maintain protective antibody levels. Large populations of older adults may be susceptible to diphtheria in both developed as well as in developing countries.
In countries with low disease incidence, the diagnosis may not be considered by clinicians and laboratory scientists. Prior antibiotic treatment can prevent recovery of the organism. Because the disease is rarely seen in developed countries, most physicians would never have seen a case of diphtheria in their lifetime. There is limited epidemiologic, clinical, and laboratory expertise on diphtheria.
National surveillance is conducted through the National Notifiable Disease Surveillance System (NNDSS). Cases are also identified by requests for diphtheria antitoxin (DAT); since 1997 DAT is available for U.S. providers only through CDC.
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