Page last reviewed: 13/07/2011

Diphtheria is a contagious bacterial infection that mainly affects the nose and throat. Less commonly, it can also affect the skin. The symptoms of diphtheria include:

  • high temperature (fever) of 38°C (100.4°F) or above,
  • sore throat, and
  • breathing difficulties.

Children are particularly vulnerable to the effects of diphtheria. The most serious cases of diphtheria can be fatal.

An estimated 5-10% of people who get diphtheria will die from complications that arise from the condition, such as breathing difficulties or inflammation of the heart (myocarditis).

How common is diphtheria?

Before a vaccination programme was introduced in Ireland, diphtheria was a very common condition and one of the leading causes of death in children.

The vaccination programme was very successful. The last case (and death ) in Ireland was in 1967.However, there is a risk that an outbreak could occur if the number of people who are vaccinated falls below a certain level.

This risk was demonstrated by the epidemic that struck the countries of the former Soviet Union between 1990 and 1998, which resulted in 157,000 cases and 5,000 deaths.

The epidemic was thought to be caused by an increase in the number of children who were not vaccinated against diphtheria. In many places the number of children immunised fell below 60%. The infection spread to adults whose immunity to the condition had weakened since they first received the vaccination as children.


All children should be vaccinated against diphtheria as part of their routine childhood vaccination schedule. Adults should consider receiving a booster vaccine when travelling to parts of the world where diphtheria is widespread. See the Prevention section for more information and advice about diphtheria vaccination.


Contagious describes a disease or infection that is easily passed from one person to another.


A disease is an illness or condition that interferes with normal body functions.


Bacteria are tiny single-cell organisms that live in the body. Some can cause illness and disease and others are good for you.


An epidemic is a sudden outbreak of disease that spreads through a population in a short time.


Vaccination or immunisation is usually given by an injection. It causes the body's immune system to produce antibodies that will fight off viruses or bacteria.


Dose is a measured quantity of a medicine to be taken at any one time.

All children should be vaccinated against diphtheria as part of their routine childhood vaccination schedule 

Page last reviewed: 13/07/2011

The symptoms of diphtheria usually begin two to seven days after you become infected.

The time it takes for symptoms to develop is called the incubation period.

Symptoms of diphtheria can include:

  • high temperature (fever) of 38ºC (100.4ºF) or above
  • chills
  • fatigue (extreme tiredness)
  • sore throat 
  • hoarse voice
  • cough 
  • headache 
  • difficulty swallowing or pain when swallowing
  • difficulty breathing
  • foul-smelling, bloodstained nasal discharge
  • swollen glands (nodes) in the neck

If you have diphtheria, a grey-white membrane can develop inside your throat. It covers the back of your throat and tonsils and can obstruct your breathing. The membrane will bleed if you try to remove it.

Diphtheria that affects the skin

Diphtheria can occasionally affect the skin rather than the throat. This is known as cutaneous diphtheria.

If you have cutaneous diphtheria, you will develop pus-filled spots on your skin, usually on your legs, feet and hands. These blisters and spots will form into a large ulcer surrounded by a red patch of discoloured, sore-looking skin. The ulcer usually heals within two to three months, but it's likely to leave a scar.

Asymptomatic diphtheria

People who have been vaccinated against diphtheria won't develop any symptoms if they become infected (asymptomatic diphtheria). However, it's still possible for these people to spread the infection to others.

Bacteria are tiny, single-cell organisms that live in the body. Some can cause illness and disease and others are good for you.
Fever is when someone's body temperature goes above the normal 37°C (98.6°F).
Immunisation or vaccination is usually given by an injection that makes the body's immune system produce antibodies that will fight off a virus.
An ulcer is a sore break in the skin or on the inside lining of the body.

Page last reviewed: 13/07/2011

Two types of bacteria can cause diphtheria.

They are:

  • Corynebacterium diphtheriae
  • Corynebacterium ulcerans

The bacteria spread when an infected person coughs or sneezes, and droplets of their saliva enter another person's mouth or nose. Less commonly, the bacteria that cause diphtheria can be transferred by an infected person onto household items, such as glasses, towels or eating utensils.

Therefore, diphtheria is usually caught after being in close, prolonged contact with someone who has the condition or is carrying the infection. For example, you may catch diphtheria from someone you live with.

In countries where standards of hygiene are poor, diphtheria can often affect the skin (cutaneous diphtheria). In such cases, the bacterial infection is spread through contact with the infected wound rather than by breathing in infected droplets.

Infection from animals

You can become infected with Corynebacterium ulcerans after being in close contact with cattle because these animals carry the bacteria in their nose and throat. You can also become infected with the bacteria after drinking unpasteurised milk or eating food that's made with unpasteurised milk.

Other animals can also carry diphtheria bacteria, such as horses, cats and dogs. Infections in humans have been reported after contact with these animals infected with the bacteria.

How the condition develops

Once a person is infected, the bacteria quickly multiply and spread through the inside surface of the mouth, throat and nose. The bacteria produce a toxin (poison), which begins to kill the cells in the throat. The dead cells rapidly build up and form the grey-white membrane in the throat

The toxin can also spread through the blood and damage the heart and nervous system.

Bacteria are tiny, single-cell organisms that live in the body. Some can cause illness and disease and others are good for you.
Contagious describes a disease or infection that is easily passed from one person to another.

Where diphtheria occurs

Diphtheria is rare in Ireland because diphtheria vaccination is part of the routine childhood vaccination schedule. However, diphtheria may be more common in countries where less people are vaccinated, such as:

  • Africa
  • South Asia
  • the former Soviet Union

Page last reviewed: 13/07/2011

Diphtheria can usually be diagnosed by checking for its distinctive symptoms (see Diphtheria - symptoms).

In particular, a grey-white membrane in the throat would strongly suggest the presence of diphtheria.


A suspected diagnosis of diphtheria can be confirmed by taking a small sample of cells from the:

  • throat
  • nose
  • wound on the skin

The sample is collected with a swab, which is similar to a cotton bud. The sample will be examined under a microscope to see whether the bacteria that cause diphtheria are present.

Diphtheria must be treated quickly to prevent serious complications developing. Therefore, if diphtheria is suspected, treatment is likely to begin before any test results are confirmed.

Page last reviewed: 13/07/2011

If diphtheria is suspected, you will be immediately referred to hospital and admitted to an isolation ward to prevent the infection spreading.

If the grey-white membrane is making it difficult for you to breathe, some or all of it will be removed.

A diphtheria infection is treated using two types of medication:

  • antibiotics to kill the diphtheria bacteria
  • antitoxins to neutralise the effects of the toxin produced by the bacteria

Most people who have diphtheria require a 14-day course of antibiotics. After this time, you'll have tests to find out if all the bacteria have gone. If diphtheria bacteria are still present, you may need to continue taking antibiotics for another 10 days. Your recommended dose will vary depending on how severe your condition is and how long you've had diphtheria.

Once you have completed the treatment, you won't be infectious to other people. However, you won't be able to leave the isolation ward until tests show that you're completely free of infection.

You should have the diphtheria vaccination after you've been treated because having diphtheria doesn't always prevent diphtheria from infecting you again.

Testing and treating close contacts

Anyone who has had close contact with you, such as family or household members, visitors and anyone you have kissed or had sex with, should visit their GP immediately to be checked for signs of diphtheria.

Testing for diphtheria involves taking a sample of cells from the nose to test for the diphtheria bacteria. Your close contacts will be prescribed antibiotics. It's very important that they finish the course. If necessary, they will also be given a booster dose of the diphtheria vaccination.

Any healthcare workers who have cared for someone with diphtheria may also need to be tested and treated.

The risk of catching diphtheria from work colleagues or school friends is very low.

Cutaneous diphtheria

Cutaneous diphtheria is diphtheria that affects the skin rather than the throat. It's treated by thoroughly washing any wounds that are infected with the diphtheria bacteria with soap and water. You'll be tested two weeks later to ensure that all of the bacteria have gone.

Antibiotics are medicines used to treat infections caused by micro-organisms, usually bacteria or fungi. Examples of antibiotics include amoxicillin, streptomycin and erythromycin.
Bacteria are tiny, single-cell organisms that live in the body. Some can cause illness and disease and others are good for you.

Page last reviewed: 13/07/2011

Diphtheria can lead to potentially life-threatening complications.

Respiratory failure

Diphtheria can cause serious breathing difficulties because:

  • the membrane that covers your throat can make breathing difficult
  • small particles of the membrane can fall down into your lungs, leading to widespread inflammation of the lungs

There's a risk that someone with diphtheria will lose much or all of their normal lung function. This is called respiratory failure.

If you're considered at risk of respiratory failure, an artificial breathing machine called a ventilator will be used to help with your breathing. The ventilator will move oxygen-enriched air in and out of your lungs while the underlying infection is treated.


The toxin that's produced by the diphtheria bacteria can inflame the muscles of your heart. Inflammation of the heart muscles is known as myocarditis.

Myocarditis can cause your heart to beat irregularly, most often causing heart block. This is when the electrical pulses that control the beating of your heart are disrupted, causing your heart to beat very slowly (bradycardia). The heart block can be treated with a temporary pacemaker. This is a small electrical device that's similar to a battery. It can be inserted into your chest to help your heart beat regularly.

In the most serious cases of myocarditis, the heart can become so weak that it can't pump blood around your body, and you will have heart failure.

Nervous system complications

Diphtheria can cause complications that affect the nervous system (neurological complications). These can occur weeks after your first experience diphtheria symptoms.

Paralysis of the diaphragm

One possible complication is your diaphragm being paralysed. Your diaphragm is a thick dome-shaped muscle that separates your chest from your abdomen. It helps you breathe in and out.

Without a functioning diaphragm, you need a ventilator to help you breathe. This can replicate the function of your diaphragm by regulating the pressure of your lungs. Unless you're put on a ventilator immediately, paralysis of the diaphragm can be fatal.

The diaphragm can become paralysed very suddenly, over half an hour or so. It can become paralysed weeks after you first develop diphtheria. You may have recovered from the initial infection and any other complications, but paralysis of the diaphragm can still occur. For this reason, children with diphtheria and other complications, such as those affecting the heart, may be kept in hospital for up to six weeks, even if they appear to be better. 

Bladder problems

Another possible complication is problems with the nerves controlling your bladder (neurogenic bladder dysfunction). If these nerves are damaged, you won't be able to fully empty your bladder. This can cause symptoms such as:

  • needing to urinate often
  • only passing a small amount of urine
  • losing control of your bladder

Bladder problems often develop before paralysis of the diaphragm, so this can be an early warning sign that you'll develop more serious breathing problems.

Malignant diphtheria

Malignant diphtheria, also known as hypertoxic diphtheria or diphtheria gravis, is a very severe form of diphtheria. As well as the other symptoms of diphtheria, people with malignant diphtheria develop:

  • severe bleeding problems
  • kidney failure

Malignant diphtheria is often fatal. It's likely to be caused by a particular type of the Corynebacterium diphtheriae bacteria that cause diphtheria.

Page last reviewed: 13/07/2011

The most effective way of preventing diphtheria is to ensure that all of your and your family's vaccinations are up to date.

Vaccinations for diphtheria are part of the routine childhood vaccination schedule. For most people, five doses provide a good level of protection against diphtheria.

Diptheria vaccine is part of the 6 in 1 vaccine that is given to babies at 2, 4 and 6 months of age. The 6 in 1 vaccine protects against:


A booster dose of diphtheria vaccine is also recommended for children at four to five years of age as part of the 4 in 1 vaccine. This protects against diphtheria, tetanus, whooping cough and polio.


A final booster dose of vaccine should be given to children in 1st year of second level school as part of the Tdap vaccine that is offered to students. This protects against tetanus, diphtheria and pertussis (whooping cough).

If you're not sure whether your family's vaccinations are up to date, you should ask at your GP surgery.

Travel vaccinations

Further booster vaccinations may be required if you're going to live or work in parts of the world where diphtheria is widespread. You should have a booster dose if your last dose was more than 10 years ago.

Regions that are known to have high rates of diphtheria include:

  • sub-Saharan Africa (all the countries to the south of the Sahara Desert, particularly Nigeria)
  • India
  • Nepal
  • Bangladesh
  • Indonesia
  • Philippines
  • Vietnam
  • Laos
  • Papa New Guinea
  • Brazil
  • Iraq
  • Afghanistan

However, the areas that are considered to be high risk for any disease can change.

In the countries that had a diphtheria epidemic in the 1990s, diphtheria rates have now fallen. The countries affected were those that made up the former Soviet Union.

However, you may wish to have a booster vaccination as a precaution if you're visiting any of the countries of the former Soviet Union, such as:

  • Russia
  • Ukraine
  • Latvia
  • Belarus
  • Estonia  

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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