La difterite è un'infezione causata dal batterio Corynebacterium diphtheriae.

Diphtheria is usually spread between people by direct contact or through the air. It may also be spread by contaminated objects. Some people carry the bacteria without having symptoms, but can still spread the disease to others. The three main types of C. diphtheriae cause different severities of disease.

The symptoms are due to a toxin produced by the bacteria. Diagnosis can often be made based on the appearance of the throat with confirmation by microbiological culture. Previous infection may not protect against future infection.

In 2015, 4,500 cases were officially reported worldwide, down from nearly 100,000 in 1980. About a million cases a year are believed to have occurred before the 1980s. Diphtheria currently occurs most often in sub-Saharan Africa, India, and Indonesia. In 2015, it resulted in 2,100 deaths, down from 8,000 deaths in 1990. In areas where it is still common, children are most affected.

It is rare in the developed world due to widespread vaccination. In the United States, 57 cases were reported between 1980 and 2004. Death occurs in 5% to 10% of those affected. The disease was first described in the 5th century BC by Hippocrates. The bacterium was identified in 1882 by Edwin Klebs.

Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Signs and symptoms may vary from mild to severe. They usually start two to five days after exposure. Symptoms often come on fairly gradually, beginning with a sore throat and fever. In severe cases, a grey or white patch develops in the throat. This can block the airway and create a barking cough as in croup.

The neck may swell in part due to enlarged lymph nodes. A form of diphtheria that involves the skin, eyes, or genitals also exists. Complications may include myocarditis, inflammation of nerves, kidney problems, and bleeding problems due to low levels of platelets. Myocarditis may result in an abnormal heart rate and inflammation of the nerves may result in paralysis.