Official State of Iowa Website Here is how you know
Iowa Department of Health and Human Services



Diphtheria is a toxin-mediated disease caused by the bacteria Corynebacterium diphtheria. Disease occurs in two main forms: respiratory and cutaneous (skin). Diphtheria is uncommon in the United States due to widespread vaccination and cases usually occur among unvaccinated or inadequately-vaccinated individuals.

Diphtheria is reportable to the Iowa Department of Public Health by Iowa Administrative Code 641/AC 1.


Symptoms of respiratory diphtheria usually appear two to five days after infection and may include:

  • Sore throat
  • Fever
  • Chills
  • Neck swelling
  • Formation of a thick, gray membrane covering the throat and tonsils
  • Difficulty breathing or rapid breathing
  • Nasal discharge
  • Inflammation of the heart (myocarditis)

Cutaneous diphtheria appears as non-healing, gray bumps on the skin which may be difficult to distinguish from other skin infections.

Infected individuals remain contagious for two to four weeks if they do not receive treatment. Persons treated with antibiotics are usually only contagious for about four days but there have been reports of people becoming carriers of the disease for up to six months after infection. Infected individuals are considered no longer contagious after two negative cultures of the nose and throat (in respiratory diphtheria) or skin lesions (in cutaneous diphtheria).


Respiratory diphtheria is transmitted person-to-person by droplet or direct contact with nasal secretions from an infected person.

Cutaneous diphtheria is more common in temperate climates and is spread person-to-person by indirect or direct contact with infected skin lesions. This form of the disease is usually mild and only rarely involves toxic complications. Crowded and unsanitary living conditions can result in spread of this form of the disease.

Raw milk may also serve as a vehicle of transmission.

Risk Factors

In the United States, diphtheria is most commonly seen in individuals who are unvaccinated or inadequately-vaccinated against the disease. Travel to areas where diphtheria is endemic, such as the Caribbean and Latin America, also increases the risk of infection. All those who share living space, food, drink, eating utensils, and/or saliva with an infected person are at risk of becoming infected.


Receiving adequate diphtheria vaccination is the best way to prevent the disease. This vaccine is one of the recommended childhood immunizations and should begin during infancy. The vaccine is usually coupled with the tetanus and pertussis (whooping cough) vaccines (DTaP vaccine). The vaccine consists of a series of five shots administered at ages:

  • 2 months
  • 4 months
  • 6 months
  • 12 to 18 months
  • 4 to 6 years

Persons over the age of 7 years who did not receive five doses of the diphtheria vaccine during their childhood should contact their health care provider to determine the best vaccine protocol available for them to become adequately vaccinated against the disease. The adult vaccine protocol usually consists of three doses of the vaccine with the second dose given one to two months after the first dose and the third dose given six months after the second dose.

Persons diagnosed with diphtheria should be placed in isolation and remain there until two negative cultures are obtained. If the infected individual is suffering from the cutaneous form of diphtheria, all skin lesions should be completely covered.

All close contacts (defined as those who sleep in the same house, share food, drink, or utensils with the infected person or those in contact with the infected person’s respiratory oral secretions) should have cultures taken from the nose and throat (in respiratory diphtheria) or skin (in cutaneous diphtheria) and should be kept under surveillance for development of the disease for seven days. Health care providers may choose to prescribe antibiotics to close contacts.


Any person who suspects they may have this disease should contact their health care provider immediately as treatment should begin as soon as possible. Treatment includes:

  • Diphtheria antitoxin. The antitoxin neutralizes the diphtheria toxin circulating in the body.
  • Antibiotics. Diphtheria is also treated with antibiotics such as erythromycin or penicillin.


No cases of diphtheria have been reported in Iowa in 2021.

For more detailed information and statistics on all notifiable diseases, please see our current annual report.

Additional Resources


Public Health


Business and Childcare

Health Care Providers