Diphtheria: symptoms and causes

Diphtheria predominantly affects children and is highly contagious, but can be prevented by vaccination.

Diphtheria is an infectious disease of bacterial origin, affecting the respiratory tract, mostly the mucous membranes of the nose and throat.

Thanks to vaccination coverage, in Italy the incidence has dropped strongly and today there have been no cases since 1996.

According to the World Health Organization, a total of 2013,4 cases occurred worldwide in 680. Although it is not an epidemic, it is certainly a phenomenon that should not be ignored.

Diphtheria mainly affects children, sometimes with serious consequences and complications, which in some cases can lead to death.

What causes it?

Diphtheria is caused by different bacterial strains belonging to the species Corynebacterium diphtheriae (gravis, mitis, intermedius and belfanti) that can be distinguished both by shape and by chemical point of view. All except C. diphtheriae belfanti can produce diphtheria toxin. It is a substance released by the infectious agent as soon as it manages to enter our body. Its action is to attack, damage or even destroy, organs and tissues.

Bacteria multiply near or directly on the surface of the mucous membranes of the throat, pharynx and larynx. However, the areas of the body affected can vary depending on the bacterium responsible for the infection, which can affect the throat, nose and sometimes the tonsils, or, especially in tropical areas, can cause skin ulcers. More rarely, the infection involves the vagina or conjunctiva.

In addition to C. diphtheriae, two other bacterial species can produce this dangerous toxin: Corynebacterium ulcerans and Corynebacterium pseudotuberculosis. Human C. ulcerans infections are associated with skin lesions and are generally caused by contact with infected animals, both pet and farmed, and by the consumption of raw milk. Human infections caused by C. pseudotuberculosis are very rare and associated with occupational exposure.

How is diphtheria transmitted?

Contagion usually occurs through direct contact with an infected person.

Transmission of the disease can occur mainly through two routes:

• inhalation of airborne droplets of saliva, which result from sneezing or coughing of an infected person; This represents the most common and effective way of diffusion, especially in situations, such as schools or aggregation centers, frequented simultaneously by many people
• contact with contaminated objects, such as tissues, glasses or other materials on which secretions produced by a person with diphtheria may have accumulated, including towels or toys.

Those who have been infected with the bacterium, but do not follow any therapy, can infect other people for up to 6 weeks, even if they do not show any obvious symptoms. Patients who have received adequate treatment with antibiotics, on the other hand, are infectious for a limited period: less than 4 days.

Although the disease can strike at any age, diphtheria mainly affects unvaccinated children. In countries with a temperate climate, this disease spreads during the winter months.

What are the symptoms of diphtheria?

The incubation period following infection can last from 2 to 7 days.

When the bacterium affects the airways, symptoms such as:

• the appearance of the typical membrane, thick, greyish in color and with inflamed margins, covering the throat and tonsils (sometimes, these lesions can lose blood, assuming a greenish or black color)
• sore throat, cough and hoarseness
• enlargement of the lymph nodes at the level of the neck
• difficulty breathing or wheezing, with airway obstruction
• mucus from the nose
• fever and chills
• loss of appetite
• general malaise.

In some people, diphtheria causes only mild discomfort, if not the absence of relevant symptoms. In these cases, the disease could also be confused with other less serious ones, such as influenza, and therefore not treated adequately, increasing the risk of spreading the disease.

Not only airways: cutaneous diphtheria

Cutaneous diphtheria occurs when diphtheria toxin affects the skin and causes symptoms such as:

• pain
• blush
• swelling.

These are symptoms that are observed in limited areas of the skin, similar to those caused by other bacterial infections.

This variant of diphtheria disease is mostly common in tropical climate zones. However, it can also occur in our latitudes, among people who live in poor hygiene conditions and in very crowded environments.

Although diphtheria can affect the skin, this disease should not be confused with other exanthematous diseases typical of childhood, such as measles or chickenpox.

Diphtheria: complications

Generally the disease has a benign course, but in some cases even serious complications can occur.

If the patient is not undergoing treatment, the first, most immediate, risk is that of suffocation: the membranes that appear on the throat and tonsils due to the proliferation of the bacterium, in fact, can partially or completely obstruct the flow of air through the respiratory tract.

The disease can also evolve by involving several other organs, such as the heart and kidneys.

In particular, at the cardiac level, complications may occur such as:

• Arrhythmias
• risk of cardiac arrest
• myocarditis
• heart failure.

Diphtheria toxin can also act on the nervous system, causing paralysis of the spinal nerves, with very serious consequences on the whole organism.

A swab is enough to detect diphtheria

The suspicion of diphtheria arises when the doctor observes the presence of the typical grayish membrane on the tonsils and throat. The diagnosis should be confirmed by laboratory analysis of the material taken by swab.

In the case of suspected cutaneous diphtheria, the doctor can take the material from the infected lesions to perform laboratory analyzes that allow to identify the type of bacterium with which you are dealing.

Is there a cure for diphtheria?

The answer is yes.

When the diagnosis of diphtheria is certain, the doctor may prescribe therapy, which is based on the administration of:

• antitoxin, injected into a vein or muscle, which neutralizes diphtheria toxin circulating in the body
• antibiotics, such as penicillin or erythromycin, which help “cleanse” the body, eliminating the bacterium. Antibiotic therapy reduces by a few days the period in which the infected person is also contagious.

In addition, if the diagnosis of diphtheria is ascertained, it is important that the patient is placed in isolation. Since this is a highly contagious disease, it is essential to avoid that you can infect other people, to avoid the risk of an epidemic.

For this reason, treatment often takes place in the hospital, where the patient is admitted and can be isolated more easily.

Sometimes antibiotics are also prescribed to people who have come into contact with the infected patient. In addition, those who deal with a person with diphtheria should pay special attention to hygiene, washing their hands often and avoiding direct contact.

Convalescence

It is a rather debilitating disease, therefore, once healing is achieved, it is important for the patient to a period of convalescence dedicated to rest and recovery of lost physical fitness.

It is not said that those who have contracted diphtheria will not develop it again, in the course of life, since the immunity acquired as a result of the infection may not have developed completely. It is therefore advisable, in any case, to undergo the vaccine.

Prevention and vaccine

Prevention is the best strategy to maintain good health. And this is especially true when it comes to a highly contagious infectious disease such as diphtheria.

Fortunately, there is the possibility of vaccination against this and other dangerous diseases for children and adults. In particular, the vaccine that protects against diphtheria is the so-called hexavalent, which confers immunity even against:

• tetanus
• pertussis
• poliomyelitis
• hepatitis B
• Haemophilus influenzae type B

The Ministry of Health recommends the diphtheria vaccine to:

• all children in the first year of life
• All unvaccinated adults
• travelers who travel to areas where the disease is endemic.

The diphtheria vaccine consists of a serum based on diphtheria toxin that is not active, therefore not able to cause the disease, but which stimulates the immune system, favoring the production of protective antibodies.

The basic course of the vaccination procedure consists of three doses, to be practiced at the third, fifth and twelfth month of the child’s life. Next two booster doses are performed, at the ages of 6 and 14 years. At the end of the cycle, the diphtheria vaccine confers almost total protection. To maintain good immunity, however, additional boosters can be made every ten years.