Diphtheria: How It Spreads, Who Is at Risk, and How It Is Treated and Prevented

Diphtheria is a serious disease caused by a toxin made by some strains of the bacterium Corynebacterium diphtheriae. Staying up to date with vaccines is the best protection.

What it is — and isn't

Diphtheria is any illness caused by diphtheria toxin. It is the toxin, not the bacterium itself, that does the serious harm: it kills healthy tissue and can cause many serious health problems.

C. diphtheriae strains that don't make the toxin can cause infections too, but these are usually less serious, aren't called diphtheria, and are treated differently.

A computer-generated image of Corynebacterium diphtheriae. CDC.

Two forms

Symptoms and complications differ between them. More: Diphtheria Symptoms and Complications.

Who is at risk

• Close contacts of someone with diphtheria — people who live with them, are often near them, share respiratory secretions (saliva) or are exposed to wound secretions (open sores or ulcers).
• International travelers: nearly all U.S. cases are linked to travel to an affected area.
• People not up to date with diphtheria vaccines, who are at higher risk of severe respiratory diphtheria.

How it spreads

• Most often through coughs and sneezes, which release small droplets carrying the bacteria that others breathe in.
• Also by touching open sores or ulcers caused by C. diphtheriae.

Prevention

CDC recommends diphtheria vaccines for everyone. CDC.

• Vaccination is the best prevention, and CDC recommends it for everyone. More: Diphtheria Vaccination.
• Close contacts of a patient should get preventive antibiotics, and be monitored, tested, and vaccinated if not up to date. Health departments investigate every case to find contacts and make sure they are protected.

Testing and diagnosis

Providers usually diagnose diphtheria from its signs and symptoms, and if they suspect respiratory diphtheria they start treatment at once, without waiting for results.

• Swabs of the skin wound, or the back of the throat and nose, go to a lab to grow and identify bacteria — which takes time.
• If C. diphtheriae grows, CDC laboratories test whether it makes the toxin — the only way to confirm diphtheria.
• For a confirmed case, clinicians work with the health department and CDC to choose treatment and limit spread.

Treatment

• Respiratory diphtheria: usually diphtheria antitoxin plus antibiotics.
• Skin infections: generally antibiotics alone.

The antitoxin stops the toxin doing further damage; antibiotics kill the bacteria. Tests are repeated after the antibiotics to make sure the bacteria are gone.

More: CDC's communication and print resources, vaccine schedules for parents and travelers' health.

Sources

Based on "About Diphtheria," Centers for Disease Control and Prevention; a work of the United States government in the public domain. The source's stock photograph of a child's throat examination is not reproduced.