Diphtheria (from Greek: διφθέρα diphthera, meaning leather) 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 large 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 blood platelets. Myocarditis may result in an abnormal heart rate and inflammation of the nerves may result in paralysis.
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. There are three main types of C. diphtheriae causing 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 culture. Previous infection may not prevent against future infection.
The symptoms of diphtheria usually begin two to seven days after infection. Symptoms of diphtheria include fever of 38 °C (100.4 °F) or above, chills, fatigue, bluish skin coloration (cyanosis), sore throat, hoarseness, cough, headache, difficulty swallowing, painful swallowing, difficulty breathing, rapid breathing, foul-smelling bloodstained nasal discharge and lymphadenopathy. Symptoms can also include cardiac arrhythmias, myocarditis, and cranial and peripheral nerve palsies.
Laryngeal diphtheria can lead to a characteristic swollen neck and throat, or "bull neck". The swollen throat is often accompanied by a serious respiratory condition, characterized by a brassy or "barking" cough, stridor, hoarseness, and difficulty breathing, and historically referred to variously as "diphtheritic croup", "true croup", or sometimes simply as "croup". Diphtheritic croup is extremely rare in countries where diphtheria vaccination is customary. As a result, the term "croup" nowadays most often refers to an unrelated viral illness that produces similar but milder respiratory symptoms.
Diphtheria is caused by the bacterium Corynebacterium diphtheriae.
Quinvaxem is a widely administered pentavalent vaccine, which is a combination of five vaccines in one that protect infantile children from Diphtheria, among other common child diseases. Diphtheria vaccine is usually combined at least with tetanus (Td) and often with pertussis (DTP, DTaP, TdaP) vaccines, as well.
The current clinical case definition of diphtheria used by the United States' Centers for Disease Control and Prevention (CDC) is based on both laboratory and clinical criteria.
- Isolation of Corynebacterium diphtheriae from a gram stain or throat culture from a clinical specimen, or
- Histopathologic diagnosis of diphtheria by a stain called "Albert's Stain".
- Upper respiratory tract illness with sore throat
- Low-grade fever (>102 °F (39 °C) is rare)
- An adherent, dense, grey pseudomembrane covering the posterior aspect of the pharynx. In severe cases, it can extend to cover the entire tracheobronchial tree.
- Probable: a clinically compatible case that is not laboratory-confirmed and is not epidemiologically linked to a laboratory-confirmed case
- Confirmed: a clinically compatible case that is either laboratory-confirmed or epidemiologically linked to a laboratory-confirmed case
Empirical treatment should generally be started in a patient in whom suspicion of diphtheria is high.
The prognosis ranges from good to poor, depending how early the infection is treated, and how the patient responds to the treatment. If the patient develops sepsis or bacteremia, or if there's cardiac involvement, the prognosis is usually poor. The mortality rate is highest in patients less than 5 years old and in the ones older than 40. The average rate of mortality from is about 5%-10%
The disease may remain manageable, but in more severe cases, lymph nodes in the neck may swell, and breathing and swallowing will be more difficult. People in this stage should seek immediate medical attention, as obstruction in the throat may require intubation or a tracheotomy. Abnormal cardiac rhythms can occur early in the course of the illness or weeks later, and can lead to heart failure. Diphtheria can also cause paralysis in the eye, neck, throat, or respiratory muscles. Patients with severe cases will be put in a hospital intensive care unit and be given a diphtheria antitoxin. Since antitoxin does not neutralize toxin that is already bound to tissues, delaying its administration is associated with an increase in mortality risk. Therefore, the decision to administer diphtheria antitoxin is based on clinical diagnosis, and should not await laboratory confirmation.
Antibiotics have not been demonstrated to affect healing of local infection in diphtheria patients treated with antitoxin. Antibiotics are used in patients or carriers to eradicate C. diphtheriae and prevent its transmission to others. The CDC recommends either:
- Erythromycin (orally or by injection) for 14 days (40 mg/kg per day with a maximum of 2 g/d), or
- Procaine penicillin G given intramuscularly for 14 days (300,000 U/d for patients weighing <10 kg and 600,000 U/d for those weighing >10 kg). Patients with allergies to penicillin G or erythromycin can use rifampin or clindamycin.
In cases that progress beyond a throat infection, diphtheria toxin spreads through the blood and can lead to potentially life-threatening complications that affect other organs, such as the heart and kidneys. The toxin can cause damage to the heart that affects its ability to pump blood or the kidneys' ability to clear wastes. It can also cause nerve damage, eventually leading to paralysis. About 40% to 50% of those left untreated can die.