Report Immediately by Phone
Hospital: Report immediately by phone
Lab: Report immediately by phone
Physician: Report immediately by phone
Local Public Health Agency (LPHA): Follow-up required. Iowa Department of Public Health will lead the follow-up investigation.
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure fax: (515) 281-5698
Diphtheria is caused by toxin-producing Corynebacterium diphtheriae, a gram-positive, irregularly-staining bacterium. Not all Corynebacterium diphtheriae produce toxin. The four strains or biotypes of C. diphtheriae in order of their likelihood to produce toxin are gravis, mitis, intermedius, and belfanti.
B. Clinical Description
Symptoms: Diphtheria has two forms—respiratory and cutaneous. This chapter deals mainly with respiratory diphtheria. Respiratory (nasal, pharyngeal, tonsillar, and laryngeal) diphtheria is typically caused by toxin-producing (toxigenic) strains of C. diphtheriae. In the respiratory form of the disease a membrane, usually visible on the throat or tonsils, is formed. Respiratory diphtheria begins 2 - 5 days after infection. Initial symptoms include a sore throat and low-grade fever. Swelling of the neck (“bull-neck”) can develop from inflammation, and is a sign of severe disease. Persons can die from asphyxiation if the membrane obstructs breathing. Remote effects of the diphtheria toxin can cause complications including myocarditis (inflammation of the heart muscle) and nerve paralysis. The respiratory form of diphtheria usually lasts several days, but complications can persist for months.
Membranous pharyngitis from nontoxigenic C. diphtheriae is also reportable, although disease is usually mild and does not cause systemic complications. The isolation of C. diphtheriae from the throat does not necessarily indicate a pathogenic role. Although the frequency with which this occurs is unknown, a small percentage of the population may carry nontoxigenic or toxigenic strains of C. diphtheriae without disease symptoms. Rarely, other Corynebacterium species (C. ulcerans or pseudotuberculosis) may produce diphtheria toxin and lead to classic respiratory diphtheria. Note: Other pathogens can cause a membrane of the throat and tonsils, including Streptococcus species, Epstein-Barr virus and cytomegalovirus, Candida, and anaerobic organisms (Vincent’s angina).
Onset: The onset is indistinguishable from the common cold, usually characterized by a mucopurulent nasal discharge (containing both mucus and pus), which may become blood-tinged. A white to grayish membrane usually forms on the nasal septum and throat in respiratory disease.
Complications: The severity of the disease and complications are generally related to the extent of local disease. When absorbed, the toxin affects organs and tissues distant from the site of invasion. The most frequent complications of diphtheria are myocarditis and neuritis.
Myocarditis may present as abnormal cardiac rhythms, and can occur early in the course of the illness or weeks later, and lead to heart failure. If myocarditis occurs early, it is often fatal.
Neuritis most often affects motor nerves and usually resolves completely. Paralysis of the soft palate is most frequently seen during the third week of illness. Eye muscles, limbs, and diaphragm paralysis can occur after the first week. Secondary pneumonia and respiratory failure may result from diaphragmatic paralysis.
Other complications include otitis media, and respiratory insufficiency due to airway obstruction, especially in infants.
The overall case-fatality rate for respiratory diphtheria is 5% - 10%, with higher death rates (up to 20%) in persons <5 and >40 years of age. The case-fatality rate for diphtheria has changed very little during the last 50 years, and is higher for those who have never received vaccine than for those who have been fully immunized.
Humans are the only known reservoir of C. diphtheria, which is present in discharges from the nose, throat, and eye and skin lesions for 2 - 6 weeks after infection.
D. Modes of Transmission
Diphtheria is transmitted person-to-person by droplet or direct contact with an infected person’s nasopharyngeal secretions. Contact with articles soiled with discharges from cutaneous lesions can be a source, but this has rarely been documented. Raw milk contaminated with Corynebacterium diphtheriae has served as a vehicle for transmission.
E. Incubation period
The incubation period is usually 2 - 5 days but may occasionally be longer.
F. Period of Communicability or Infectious Period
The infectious period is variable, typically lasting 2 weeks or less. Antibiotic treatment promptly terminates shedding, usually in less than 4 days; but chronic carriage may occur, even after antimicrobial therapy. Patients are considered infectious until two successive pairs of nose and throat cultures obtained not <24 hours after completion of antimicrobial therapy and > 24 hours apart are negative. (See Section 3) B. 2. d [page 5] for more details.) Asymptomatic carriers are important in sustaining transmission. If cultures remain positive, contact IDPH, CADE at (800) 362-2736 for further guidance.
Infection can occur in immunized, partially immunized and unimmunized persons, but it is usually less severe in those who are partially or fully immunized. Diphtheria is endemic in many parts of the world, including countries of the Caribbean and Latin America. The incidence of respiratory diphtheria is greatest in the fall and winter. During the last few years, large epidemics of respiratory diphtheria, primarily in adolescents and adults, have occurred in the former Soviet Union, Algeria, and Ecuador. In the states of the former Soviet Union (including Russia, the Ukraine and Central Asian Republics), more than 150,000 cases and 5,000 deaths from diphtheria occurred between 1990 and 1997. In recent epidemics in the former Soviet Union, the case fatality rate has ranged from 3% to 23%. In 2011, 4,887 cases of diphtheria were reported worldwide to the World Health Organization (WHO), but many more cases likely go unreported.
The last reported case in Iowa occurred in 1967. It is estimated that more than 40% of US adults lack protective levels of circulating antitoxin.
H. Bioterrorism Potential
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Diphtheria can be found at: wwwn.cdc.gov/NNDSS/script/casedefDefault.aspx
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
Note on Cutaneous diphtheria
Cutaneous diphtheria, caused by either toxigenic or nontoxigenic strains, is usually mild, typically consisting of nondistinctive sore or shallow ulcers, and only rarely involving toxic complications (1-2% of infections with toxigenic strains). Cutaneous diphtheria was removed from the nationally reportable disease list in 1980, but it remains reportable in Iowa.
Place the cutaneous case in contact precautions until two cultures of skin lesions are negative. Material for all these cultures should be taken not <24 hours after cessation of antimicrobial therapy and > 24 hours apart. If cultures remain positive, contact IDPH, CADE at (800) 362-2736 for further guidance. If there was no antimicrobial therapy, the cultures should be taken after symptoms resolve, > 2 weeks after their onset, and > 24 hours apart.
Work restrictions are the same as for respiratory diphtheria.
American Academy of Pediatrics. Red Book 2003: Report of the Committee on Infectious Diseases, 26th Edition. Illinois, Academy of Pediatrics, 2003.
CDC. Epidemiology & Prevention of Vaccine-Preventable Diseases: The Pink Book, 12th Edition. CDC, January, 2011.
CDC. Vaccine-Preventable Disease Surveillance Manual, 4th Edition, 2008-09.
Heymann, D., ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.
IDPH. Public Health (641) Chapter 1, Notification and Surveillance of Reportable Communicable and Infectious Diseases, Poisonings and Conditions (Printed April 2004).