Diphtheria is caused by a bacteria that is easily spread from person to person. The infection affects your airways, tonsils, throat, nose and sometimes the skin. The bacteria can produce dangerous toxins which, if left untreated can lead to breathing problems, heart problems, kidney failure, paralysis or may even be life threatening.

How is diphtheria spread?

Diphtheria is very contagious. It is spread from person to person by breathing in droplets produced after an infected person coughs, sneezes or laughs. It can also be spread by contact with items such as drinking glasses, used tissues, bedding or clothing which have been contaminated by a person with diphtheria.

Who is most at risk?

  • Coming into contact with an infected person puts you at greatest risk of getting diphtheria, especially if you have not been immunised against it.
  • Living in crowded environments and poor hygiene practices may also increase your risk.
  • Most cases have been reported in children under 10 years of age.

What are the symptoms of diphtheria?

The common symptoms of diphtheria include:

  • a severe sore throat
  • thick grey-white coating at the back of the throat
  • a high temperature (fever) of 38°C or above
  • breathing difficulties.

Other symptoms are chills, tiredness, hoarse voice, cough, headache, difficulty swallowing or pain when swallowing and unpleasant smelling nose discharge. Initially diphtheria is often mistaken for a sore throat or throat infection, but the symptoms quickly get worse. 

Some people may carry the diphtheria bacteria and spread the infection, even though they themselves do not develop symptoms.   

Diphtheria affecting the skin

Diphtheria can sometimes affect the skin rather than the throat – known as cutaneous diphtheria. The symptoms of cutaneous diphtheria are pus-filled blisters or spots on your skin, usually on your hands, legs and feet. These blisters will form into a large ulcer which usually heals within 2 to 3 months, but it's likely to leave a scar.

How is diphtheria diagnosed?

Depending on your symptoms, your doctor will take a sample of cells from the throat, nose or wound on the skin. This is sent to the laboratory and will be examined to see whether the bacteria that cause diphtheria are present.

How is diphtheria treated?

People suspected of having diphtheria will be given an antitoxin injection into the muscle or vein. The antitoxin works by counteracting the diphtheria toxin present in the bloodstream. Since diphtheria is caused by a bacteria, it is treated with antibiotics. Diphtheria must be treated quickly to prevent serious complications developing. Diphtheria can be fatal – 5 to 10 out of every 100 people who are infected die, even with treatment.

Reducing the spread

People with diphtheria can reduce passing it to others by:

  • Not going to school or work until you are completely recovered and had two throat swabs that are clear of the bacteria. Also avoiding large gatherings.
  • Local health officials must be notified when cases of diphtheria occur. To prevent the spread, the infected person will be advised to have minimal contact with others until they are recovered. Also, health authorities may undertake contact tracing, to identify people who may have come in contact with an infected person. They are likely to be at risk of infection.
  • People who have been in close contact with the infected person may be offered preventive doses of antibiotics.

How can I prevent diphtheria?

The best protection against diphtheria is having a complete course of three doses of diphtheria-containing vaccine and administration of booster doses. You cannot get diphtheria from the vaccine.

  • In New Zealand, the diphtheria vaccine is combined with other vaccines and is part of the national immunisation programme. Babies are immunised at 6 weeks, 3 months and 5 months old. 
  • Booster doses are given to children when they’re 4 and 11 years old.
  • To ensure protection continues, a tetanus booster is offered at 45 and 65 years of age. 
  • Even if you've had diphtheria, you will still need to immunise. Contracting diphtheria does not provide lasting immunity.
  • Read more about diphtheria vaccines.

Learn more

Diphtheria Ministry of Health, New Zealand
Diphtheria Immunisation Advisory Centre, New Zealand


  1. Diphtheria Immunisation Handbook 2017