Dr. Izegboya Ukpebor, a senior registrar in the Department of Oral Pathology and Medicine at the University of Benin Teaching Hospital in Edo State, discusses the causes, symptoms, risk factors, and treatment of diphtheria in an interview with Alexander Okere. Diphtheria is a serious bacterial infection caused by the bacterium Corynebacterium diphtheriae. There are two primary types of diphtheria: respiratory and cutaneous. Respiratory diphtheria affects the nose, throat, and tonsils, while cutaneous diphtheria affects the skin. The disease is primarily caused by the toxin produced by the bacterium, which can lead to severe illness.
Diphtheria bacteria are transmitted from person to person, typically through respiratory droplets released when an infected individual coughs or sneezes. Infection can also occur through contact with infected skin lesions, open sores, or contaminated clothing and objects. Notably, no significant reservoirs for C. diphtheriae other than humans have been identified. When an infection occurs, the pathogenesis of diphtheria depends on two main factors: the strain’s ability to colonize the nasopharyngeal cavity or skin and its capacity to produce diphtheria toxin. If a person is infected with a toxin-producing strain, the toxin can enter the bloodstream, potentially causing damage to the kidneys, heart, and nerves. This may lead to myocarditis, which is inflammation of the heart muscles, and neuropathy, characterized by nerve damage resulting in numbness, muscle weakness, pain, and tingling sensations. In contrast, variants of C. diphtheriae that do not produce the toxin typically cause milder symptoms, such as a sore throat or, in rare cases, pharyngitis.
The respiratory system is particularly affected by diphtheria because the bacterium is commonly spread via airborne droplets. When inhaled, C. diphtheriae adheres to the lining of the respiratory system. Although diphtheria can involve almost any mucous membrane, other areas that may be infected include the conjunctiva of the eyes, vaginal tissues, and the external ear canal. The specific signs and symptoms of diphtheria depend on the variant of the bacterium involved and the affected body part. The incubation period for diphtheria typically ranges from two to five days but can extend up to ten days. In cases of skin involvement, the infection may lead to sores and ulcers.
Respiratory diphtheria can result in various symptoms, including difficulty swallowing, sore throat, weakness, swollen glands in the neck, mild fever, loss of appetite, conjunctivitis, and hoarseness if the larynx is affected. After two to three days, the released toxin can kill healthy tissue in the respiratory system, leading to a thick gray or white coating, known as a pseudomembrane, on the tonsils or back of the throat. This coating can cause difficulty in breathing, and if it extends to the larynx, it may result in hoarseness and a barking cough, posing a risk of complete airway obstruction. When the infection affects tissues outside the throat and respiratory system, such as the skin, the illness is generally milder, as the body absorbs lower amounts of the toxin.
Symptoms of diphtheria typically become visible within two to ten days after exposure to the bacteria. It is also possible for an infected person to be asymptomatic during the incubation period, during recovery, or for an unknown duration in healthy individuals. Patients recovering from diphtheria may carry the bacteria in their pharynx or nose for several weeks, making them carriers who can spread the infection without exhibiting symptoms. An asymptomatic carrier is defined as a person with no symptoms but with laboratory confirmation of toxigenic C. diphtheriae. Untreated individuals infected with diphtheria are usually contagious for up to two weeks, with rare cases extending to four weeks. The thick gray coating on the throat of an infected person may resemble tonsillitis, which is an infection of the tonsils caused by viral or streptococcal bacteria. While tonsillitis is common among children, it can also affect teenagers and adults. The distinguishing factor between tonsillitis and diphtheria is the presence of the thick gray coating associated with the latter.
Risk factors for diphtheria include being unvaccinated, living in crowded or unsanitary conditions, traveling to areas where diphtheria is more prevalent, having an immunocompromised state, and sharing utensils with individuals infected with diphtheria. Both children and adults can exhibit similar signs and symptoms. Recent outbreaks have been reported in Lagos, Kano, Yobe, and Osun states, likely due to individuals in these areas having one or more of the aforementioned risk factors. The presence of one infected person poses a risk to close contacts, especially if they are not vaccinated or fully vaccinated, further escalating the disease within communities. According to the Nigeria Centre for Disease Control, at least 34 deaths have been recorded.
Despite being highly preventable and treatable, diphtheria can be fatal due to complications such as airway blockage, heart muscle damage, nerve injury, paralysis, lung infections, or loss of lung function. The disease persists in areas with low vaccination coverage, particularly in remote regions lacking access to basic medical care. Reports indicate that more cases are likely due to sub-optimal coverage for the third dose of the diphtheria-containing pentavalent vaccine in the country. Diagnosis of diphtheria involves a doctor assessing common signs and symptoms, including fever, neck swelling, sore throat, cough, and the characteristic white or gray coating in the throat. Laboratory testing may involve swabbing the back of the throat, nose, or skin ulcer, although treatment often begins immediately based on clinical suspicion, especially in cases of respiratory diphtheria.
The first step in treating diphtheria is administering an anti-toxin injection and anti-diphtheric serum to counteract the toxin produced by the bacteria. This treatment is crucial for respiratory diphtheria but is rarely used for cutaneous infections. Additional treatment includes antibiotics such as erythromycin or penicillin, which help clear infections in the respiratory system, skin, and other areas, including the eyes. Antibiotics may also be prescribed for individuals in close contact with the patient. After 48 hours of antibiotic treatment, patients typically are no longer contagious, but completing the full course of antibiotics is essential to ensure the bacteria are fully eradicated from the body.
During treatment, patients may need to be hospitalized to prevent the spread of infection to others. Respiratory diphtheria can be particularly deadly, with about one in ten patients likely to die from the condition. Without treatment, the mortality rate can rise to 50 percent. Vaccines are one of the most effective methods for preventing diphtheria. These vaccines are derived from a purified toxin removed from a variant of the bacterium. There are four vaccines available that protect against diphtheria: DTaP and Tdap, which protect against diphtheria, tetanus, and pertussis (whooping cough), and DT and Td, which protect against diphtheria and tetanus. Modern vaccination schedules include the diphtheria toxoid DTaP as part of childhood immunization, with recommendations for doses at two months, four months, six months, 15 to 18 months, and four to six years. For those aged 11 to 13 years, the Tdap shot is recommended, and women should receive the Tdap vaccine during the second half of pregnancy. Adults are advised to receive the Td or Tdap vaccine every ten years.
While five doses of the DTaP vaccine for children and one Tdap shot for preteens are recommended for optimal protection against diphtheria, these vaccinations do not provide lifetime immunity. Booster shots are necessary to maintain protection. Ultimately, the best form of prevention against diphtheria is vaccination. The Centre for Disease Control also recommends that close contacts of individuals with diphtheria receive antibiotics to prevent illness.
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