Diphtheria

Diphtheria is a serious infection caused by the bacterium Corynebacterium diphtheriae.

While many people experience no symptoms, others can become very ill. In major outbreaks, the mortality rate can approach 10%. The disease is characterized by its ability to cause severe respiratory issues and systemic complications. It can affect the skin, eyes, or genitals. It also impacts vital organs through the spread of a potent toxin. This makes it a significant concern for global public health.

The severity of the disease depends on a specific mechanism involving an exotoxin.

This toxin is only produced when the bacteria are infected by a particular bacteriophage. This process is known as lysogenic conversion. The bacteria carry a tox gene that encodes the diphtheria toxin (DT). The toxin is a protein that splits into two parts. The B fragment helps the toxin enter host cells. Once inside, the A fragment is released into the cytoplasm. This fragment stops the cell from making new proteins. It does this by modifying a protein called elongation factor EF-2. Without this protein, the cell cannot perform protein translation.

As the infection progresses, it creates visible physical changes in the throat. The toxin destroys healthy tissues in the respiratory system. This dead tissue forms a thick, grey or white coating called a pseudomembrane. This membrane is tough and leathery in texture. It can grow to cover the nose, tonsils, or the voice box. If the pseudomembrane blocks the airway, it can lead to strangulation. Patients often develop a characteristic "barking" cough. This is sometimes called diphtheritic croup. The neck may also swell significantly due to enlarged lymph nodes. This swelling is often referred to as a "bull neck."

History shows that humans have recognized this illness for millennia. Hippocrates first described the disease in the 5th century BC. However, the specific cause remained a mystery for a long time. In 1882, Edwin Klebs identified the bacterium Corynebacterium diphtheriae.

This discovery allowed scientists to understand the biological nature of the infection. It paved the way for modern diagnostic and preventative methods. Understanding the bacterium changed how doctors approached outbreaks and patient care.

Global data shows a massive shift in the impact of diphtheria.

] Before the 1980s, about one million cases occurred every year. In 1980, there were nearly 100,000 reported cases. By 2015, official reports dropped to 4,500 cases worldwide. Deaths also decreased from 8,000 in 1990 to 2,100 in 2015. Today, the disease is most common in sub-Saharan Africa, South Asia, and Indonesia. In the United States, only 57 cases were reported between 1980 and 2004. This decline is largely due to widespread immunization programs.

Treatment focuses on both the bacteria and the effects of the toxin. Doctors use antibiotics like erythromycin or benzylpenicillin to kill the bacteria. These help stop the person from spreading the infection to others. For the toxin, doctors administer diphtheria antitoxin. This consists of antibodies taken from the serum of horses. Because the toxin binds to tissues quickly, antitoxin must be given early. In severe cases, a tracheotomy may be required to open the airway. Complications can include myocarditis, which affects the heart rate. It can also cause nerve inflammation leading to paralysis or kidney problems.

Prevention is the most effective way to manage the disease.

Vaccination uses a diphtheria toxoid, which is an inactivated version of the toxin. This teaches the immune system to produce antitoxins. Children typically receive three or four doses during childhood. These are often combined with vaccines for tetanus and pertussis. Adults should receive booster doses every ten years to maintain protection. In developing countries, pentavalent vaccines are often used. These protect against five different diseases at once. Maintaining high vaccination rates is essential to prevent the disease from re-emerging.