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.

Diphtheria is usually caught after being in close or 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 these 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 coming into close contact with cattle, because they carry the bacteria in their nose and throat.

You can also become infected with the bacteria after drinking unpasteurised milk or eating food made with unpasteurised milk.

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) that begins to kill the cells in the throat. The dead cells rapidly build up and form a grey-white membrane in the throat (see symptoms of diphtheria).

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

Diphtheria can lead to potentially life-threatening complications, such as breathing difficulties and problems with the heart and nervous system.

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.

Myocarditis

The toxin that’s produced by 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 you first experience diphtheria symptoms.

Paralysis of the diaphragm

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

If the diaphragm is not working properly, you will need a ventilator to help you breathe. This can mimic the function of your diaphragm by regulating the pressure of your lungs. Unless you are put on a ventilator immediately, paralysis of the diaphragm can be fatal.

The diaphragm can become paralysed very suddenly, over the period of half an hour or so. It can become paralysed weeks after you first develop diphtheria, even after you have recovered from the initial infection and any other complications.

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.

The most effective way of preventing diphtheria is to ensure all of your vaccinations are up-to-date.

Vaccinations for diphtheria are part of the routine NHS childhood vaccination schedule.

In total, children should receive five doses of the diphtheria vaccination. It’s usually combined with other vaccines. For most people, five doses provide a good level of protection against diphtheria for the rest of their life.

Babies

All babies are offered vaccination against diphtheria as part of the 5-in-1 vaccine that is given when they’re two, three and four months old. The 5-in-1 vaccine, also known as the DTaP/IPV/Hib vaccine, also protects against:

• tetanus
• whooping cough
• polio
• Hib (Haemophilus influenzae type b)

Pre-school children

A booster vaccine against diphtheria is given as part of the 4-in-1pre-school booster (also called the DTaP/IPV vaccine) to children who are about three years and four months old. The 4-in-1 vaccine protects against diphtheria, tetanus, whooping cough and polio.

Teenagers

A final booster dose of diphtheria vaccine is given as part of the 3-in-1 teenage booster (also called the Td/IPV vaccine) to children when they’re 13 to 18 years old. Th 3-in-1 vaccine protects against diphtheria, tetanus and polio.

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

Travel vaccination against diphtheria

Further booster diphtheria 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 known to have high rates of diphtheria include:

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

However, the areas that are considered to be high risk for any disease can change. For up-to-date travel information, you can check:

• NHS fitfortravel 
• National Travel Health Network and Centre (NaTHNaC)

Diphtheria is a contagious bacterial infection that mainly affects the nose and throat. Less commonly, it can also affect the skin.

Diphtheria is highly contagious. The bacteria spread when an infected person coughs or sneezes and droplets of their saliva enter another person’s mouth or nose.

Diphtheria is very rare in England because most people have been vaccinated against it.

The symptoms of diphtheria include:

• a high temperature (fever) of 38ºC (100.4ºF) or above
• sore throat
• breathing difficulties
• a grey-white membrane developing in the throat

Diagnosing diphtheria

A diagnosis of diphtheria can be confirmed by taking a swab of the throat, nose or wound on the skin. A swab is similar to a cotton bud and collects a small sample of cells.

The sample will be examined under a microscope to see whether the bacteria that cause diphtheria are present.

Treating diphtheria

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

Diphtheria is treated with antibiotic and antitoxin medicine. Anyone suspected of having the condition will be put in isolation when they are admitted to hospital.

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

An estimated 5-10% of people who get the infection will die from complications of diphtheria, such as breathing difficulties, inflammation of the heart (myocarditis) or problems with the nervous system.

Vaccination

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

Adults should consider having a booster vaccine when travelling to parts of the world where diphtheria is widespread.

Read more information about the diphtheria vaccination.

How common is diphtheria?

Before a vaccination programme was introduced in 1940, diphtheria was a very common condition and one of the leading causes of death in children.

The vaccination programme has been very successful. Since 1986, there have been only 15 recorded cases of diphtheria in England and Wales, and no deaths. Diphtheria is a notifiable disease, which means that if a doctor diagnoses the condition, they must tell the local authority.

Even though the incidence of diphtheria in England is low, there’s 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 diphtheria epidemic that struck the countries of the former Soviet Union between 1990 and 1998. It resulted in 157,000 cases and 5,000 deaths. The epidemic was caused by an increase in the number of children who were not vaccinated against the disease.

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:

• a 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
• pale, blue skin

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.

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

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 you getting the infection 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 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.