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Pronounced: Dif-THEER-e-uh

En Español (Spanish Version)


Diphtheria is a highly contagious and life-threatening infection caused by bacteria. The infection most commonly attacks the mucus membranes associated with the breathing system (the tonsils, throat, and nose) and can also infect the skin. In addition, some types of the bacteria can cause damage to the heart, nerves, kidneys, and brain.

The vaccine for diphtheria is safe and is very effective at preventing the disease. A series of shots are given during childhood, then booster shots are required every ten years to keep the immunity strong.

Before vaccines and medications were available to prevent and treat the disease, nearly one out of ten people died. Diphtheria was the leading cause of death among children.

Diphtheria is a medical emergency that requires immediate care from your doctor. Not everyone who gets diphtheria shows signs of illness, though they may be able to infect others. The sooner it is treated, the more favorable the outcome.


Diphtheria is caused by the bacteria Corynebacterium diphtheriae . The infection spreads from person to person through contact with:

  • Droplets of moisture that are coughed or sneezed into the air by an infected person and breathed in by a noninfected person
  • Personal items, such as tissues or drinking glasses, that have been used by an infected person
  • Skin that is infected with diphtheria

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors include:

  • Having never been immunized against diphtheria
  • Not having had a booster dose in the past ten years
  • Living in crowded or unsanitary conditions
  • Having a compromised immune system
  • Being undernourished


Signs and symptoms of diphtheria usually begin 2 to 5 days after a person is infected. The most telltale sign of diphtheria is a gray covering on the back of the throat, which can detach and block the airway. If left untreated, the bacteria can produce a poison that spreads through the body causing damage to the heart, nerves, and kidneys.

Symptoms include:

  • Sore throat and painful swallowing
  • Fever up to 103°F
  • Swollen glands in the neck
  • Difficulty breathing
  • Difficulty swallowing
  • Weakness
  • Gray covering on the back of the throat

Swollen Lymph Nodes

Swollen lymph node

© 2008 Nucleus Medical Art, Inc.


Your doctor will ask about your symptoms and medical history, and perform a physical exam. Diphtheria will be suspected if the throat and tonsils are covered with a gray membrane. Tests to confirm a diagnosis may include:

  • A sample of the gray membrane that coats the back of the throat
  • A sample of tissue from an infected area of skin


Talk with your doctor about the best treatment plan for you. If your doctor suspects diphtheria, your treatment will start immediately, even before the lab results are returned. Treatment options include the following:

  • Antitoxin—A substance, injected into the body, which neutralizes the diphtheria poison that is traveling in the body.
  • Antibiotics—A substance, injected or given as a pill, that kills the diphtheria bacteria in the body and heals the infection. It also reduces the length of time a person is contagious.
  • Isolation and bedrest—It takes a long time, up to six weeks, to recover from diphtheria, especially if the heart was affected. Isolation may be necessary while a person is still contagious.


To help reduce your chances of getting diphtheria, take the following steps:

  • Get immunized and stay up-to-date on your immunization.
  • If you have been in contact with someone who has diphtheria, you should be watched closely for symptoms and work with a doctor to determine the appropriate treatment.


Centers for Disease Control and Prevention
National Immunization Program

National Coalition for Adult Immunization

National Foundation of Infectious Diseases (NFID)

National Institute of Allergy and Infectious Diseases

World Health Organization


BC Health Guide

Caring for Kids, The Canadian Paediatric Society


Beers MH, Fletcher AJ, Jones TV, et al. The Merck Manual of Medical Information: Second Home Edition . Whitehouse Station, NJ: Merck Research Laboratories; 2003.

Epidemiology and Prevention of Vaccine-Preventable Diseases . 8th ed (2005). Published by the National Immunization Program, Centers for Disease Control and Prevention, US Department of Health and Human Services. Available at: http://www.cdc.gov/nip/publications/pink/dip.pdf.

Last reviewed January 2008 by David Horn, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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