What Is Diphtheria?

Diphtheria

Definition

What is diphtheria?

Diphtheria is an infectious disease caused by the bacteriumCorynebacterium diphtheriae. This disease primarily affects the mucous membranes of the respiratory tract (respiratory diphtheria), although it may also affect the skin (cutaneous diphtheria) and lining tissues in the ear, eye, and the genital areas.

History

What is the history of diphtheria?

Throughout history, diphtheria was a leading cause of death among children, and it was once referred to as the "strangling angel of children." Through the ages, several epidemics struck Europe, and even the American colonies were affected by an outbreak in the 18th century. Most recently, in the 1990s, large outbreaks of diphtheria occurred in Russia and in the former independent states of the Soviet Union.

The diphtheria bacterium was first identified in the 1880s. In the 1890s, the antitoxin against diphtheria was developed, with the first vaccine being developed in the 1920s. With the development and administration of the diphtheria vaccine, the incidence of diphtheria has decreased significantly. Though it is still endemic in many parts of the world, respiratory diphtheria has now became a rare disease in the United States (with up to five cases per year). Furthermore, whereas diphtheria primarily affected younger children in the prevaccination era, an increasing proportion of cases today occur in unvaccinated or inadequately immunized adolescents and adults.

Causes

What causes diphtheria?

Diphtheria is caused by toxin-producing strains of the gram-positive bacillusCorynebacterium diphtheriae. There are four biotypes of the bacterium (gravis, mitis, intermedius, and belfanti), and each differs in the severity of disease it produces. Nontoxigenic strains are usually responsible for less severe cutaneous diphtheria.

The signs and symptoms of respiratory diphtheria are caused by the bacterium's ability to cause a localized inflammatory reaction of the cells lining the upper respiratory tract. In certain cases, the disease can become more severe and widespread, and it can involve other organs of the body as well.

How is diphtheria transmitted?

Diphtheria is transmitted to close contacts via airborne respiratory droplets or by direct contact with nasopharyngeal secretions or skin lesions. Rarely, it can be spread by objects contaminated by an infected person. Overcrowding and poor living conditions can further contribute to the spread of diphtheria.

Humans are the only known reservoir ofCorynebacterium diphtheriae. Infected individuals may develop symptoms of diphtheria, or they may become carriers of the bacteria with no symptoms (asymptomatic carriers). These asymptomatic carriers can serve as reservoirs for active infection and may transmit the disease to other individuals.

Signs and Symptoms

The symptoms of respiratory diphtheria usually begin after a two- to five-day incubation period. Symptoms of respiratory diphtheria may include the following:

Respiratory Diphtheria symptoms:

* Sore throat

* Low-grade fever

* Increased pulse

* Adherent membrane of the tonsils, pharynx, or nose

* Throat obstruction

* Neck swelling

* Enlarged neck lymph nodes

* Difficulty swallowing

* Extreme weakness

* Difficulty breathing

* High fever

* Arrhythmia

* Heart failure

* Muscle paralysis

With the progression of respiratory diphtheria, the infected individual may also develop an adherent gray membrane (pseudomembrane) forming over the lining tissues of the tonsils and/or nasopharynx. Individuals with severe disease may also develop neck swelling and enlarged neck lymph nodes, leading to a "bull-neck" appearance. Extension of the pseudomembrane into the larynx and trachea can lead to obstruction of the airway with subsequent suffocation and death.

The dissemination of diphtheria toxin can also lead to systemic disease, causing complications such as inflammation of the heart (myocarditis) and neurologic problems such as paralysis of the soft palate, vision problems, and muscle weakness.

Cutaneous diphtheria is characterized by a non-healing skin ulcer covered by a gray-brown membrane. It is typically a localized infection that is rarely associated with systemic complications.

Cutaneous Diphtheria symptoms:

* Infected skin lesions

* Painful skin

* Red skin rash

* Swollen skin

Prevention

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