Diphtheria

What causes diphtheria

Corynebacterium diphtheriae is a bacterium that lives in the nose and throat. Some strains carry a gene, delivered by a virus that infects the bacterium, that lets them produce diphtheria toxin. The toxin kills cells locally, forming the membrane, and spreads through the blood to damage the heart, nerves and kidneys. Related species (C. ulcerans, from animals and unpasteurized dairy) can also produce the toxin.

How diphtheria spreads

• respiratory droplets from coughing and sneezing
• close, prolonged contact, such as in the same household
• touching infected skin sores or, less often, contaminated objects

People are usually infectious for up to 2 weeks without treatment, and less than 48 hours after starting effective antibiotics. Some people carry the bacteria without symptoms and can still spread it.

Risk is highest in unvaccinated or under-vaccinated people, crowded living conditions, and areas where vaccination programs have been disrupted.

Symptoms

Symptoms usually begin 2 to 5 days after exposure (range 1 to 10 days).

Respiratory diphtheria

• sore throat and hoarseness
• mild fever and chills
• a thick gray or whitish membrane on the tonsils, throat or nose, which sticks firmly and bleeds if scraped
• swollen lymph glands and soft-tissue swelling in the neck, giving a "bull neck" appearance in severe cases
• difficulty swallowing and breathing, and noisy breathing (stridor)
• a bloody, foul-smelling nasal discharge when the nose is involved

Cutaneous (skin) diphtheria

Shallow, non-healing ulcers with a gray membrane, often on the legs. It is more common in tropical climates and among people experiencing homelessness. It is usually milder but spreads the infection.

Diphtheria vs other sore throats

Complications

• Airway obstruction from the membrane and swelling, the most immediate danger
• Myocarditis: inflammation of the heart muscle, typically 1 to 2 weeks after the start of illness, causing abnormal heart rhythms and heart failure
• Nerve damage (neuropathy): weakness of the palate, eye muscles and limbs, or breathing muscles, appearing weeks after infection
• Kidney damage

Even with treatment, diphtheria remains fatal in about 5% to 10% of cases, higher in young children and older adults.

Diagnosis

Because diphtheria progresses quickly, treatment is started on clinical suspicion without waiting for results. Doctors will:

• take swabs from the throat, nose and beneath the membrane, or from skin lesions, for culture
• test any isolated bacteria for toxin production
• perform an ECG and blood tests to check for heart involvement

Public health authorities must be notified immediately, so close contacts can be traced.

Treatment

• Diphtheria antitoxin (DAT): neutralizes toxin that has not yet entered cells. It is given as early as possible. In the US, it is obtained through the CDC.
• Antibiotics: erythromycin or penicillin to kill the bacteria and stop transmission.
• Hospital care and isolation until two swabs taken 24 hours apart after finishing antibiotics are negative.
• Airway support: sometimes a breathing tube or tracheostomy.
• Heart monitoring for several weeks.
• Vaccination after recovery: the illness does not reliably produce immunity.

Close contacts

Household and other close contacts are swabbed, given preventive antibiotics, and vaccinated if their immunization is not up to date. They are monitored for symptoms for 7 to 10 days.

Prevention: the diphtheria vaccine

Diphtheria toxoid vaccine is given in combination with tetanus and pertussis vaccines:

• DTaP for children: doses at 2, 4, 6 and 15 to 18 months, and 4 to 6 years
• Tdap at 11 to 12 years
• Td or Tdap boosters every 10 years for adults
• Tdap during each pregnancy, ideally at 27 to 36 weeks, mainly to protect newborns from whooping cough

The vaccine protects against the toxin, preventing severe disease. Check your vaccination status before traveling to regions with ongoing diphtheria.

Frequently asked questions

What are the symptoms of diphtheria?

Diphtheria typically starts with a sore throat, mild fever and swollen neck glands. A thick, gray membrane forms on the tonsils or throat and can make breathing and swallowing difficult. The toxin can later affect the heart and nerves.

How is diphtheria spread?

It spreads through droplets from coughs and sneezes, close contact with an infected person, and contact with infected skin sores. People without symptoms can carry and spread the bacteria.

Is diphtheria still around?

Yes. It is rare in countries with high vaccination coverage, but outbreaks continue in parts of Asia, Africa and elsewhere, especially where vaccination rates have fallen. Travelers should ensure their vaccines are up to date.

How is diphtheria treated?

Diphtheria is treated in hospital with diphtheria antitoxin to neutralize the toxin and antibiotics to kill the bacteria. Patients are isolated, the airway and heart are closely monitored, and close contacts receive preventive antibiotics and vaccination.