Diphtheria Symptoms and How It Spread

Diphtheria is a bacterial infection that commonly affects the nose and throat. A characteristic sign of a diphtheria infection is a thick, hard, grayish coating inside your throat. While diphtheria is rare in the developed world due to vaccination, it can cause serious complications, including death, if left untreated.

The widespread use of diphtheria vaccines has reduced the incidence of the disease worldwide. Between 2017 and 2022, the number of cases reported annually has hovered between around 8,000 and 23,000.

Diphtheria Symptoms and Fatalities

Diphtheria used to be a common cause of illness and death, especially in children, with a mortality rate as high as 69%. The severity of the infection led to its nickname—"the strangling angel"—in the decades before the widespread availability of diphtheria vaccines.

Even today, the risk of death overall is between 5% and 10%, while infections in younger children and adults over 40 are closer to 20%.

When someone is infected with diphtheria, respiratory symptoms usually appear within two to five days, although some take up to 10 days to develop.

Diphtheria can start similarly to a normal respiratory infection with mild flu-like symptoms. In time, however, other, more serious symptoms can develop, including:

• Severe fatigue
• Throat pain
• Nausea and vomiting
• Fever and chills
• Wheezing
• Shortness of breath
• Hoarseness and difficulty talking
  
• Rapid heartbeats (tachycardia)
• Difficulty swallowing
  

Without treatment, symptoms of diphtheria will usually last one to two weeks. However, people may experience complications for weeks or months after the initial acute infection.

Cutaneous Diphtheria

Another, less common type of diphtheria, called cutaneous diphtheria, affects the skin. At first, the infection may look similar to skin conditions like eczema or psoriasis, causing a scaly rash with oozing skin ulcers.

Although less serious than respiratory diphtheria, cutaneous diphtheria can lead to secondary skin infections if bacteria like Staphylococcus aureus get into the open skin sores.

Approximately 20% to 40% of people with cutaneous diphtheria will develop respiratory diphtheria.

Complications of Diphtheria

Diphtheria can become serious if it spreads (disseminates) beyond the respiratory tract. If this happens, it can lead to potentially life-threatening complications like:

• Sepsis (a severe immune reaction to a disseminated infection which can lead to shock)
• Myocarditis (inflammation of the heart)
• Acute kidney failure
• Liver failure
• Pneumonia
• Demyelinating polyneuropathy (inflammatory condition of the nervous system)
• Paralysis (including the paralysis of the diaphragm)
  

Causes of Diphtheria and How It Is Spread

Diphtheria can be caused by one of several strains of bacteria called Corynebacterium diphtheria. These strains release a poisonous substance called diphtheria toxin that is responsible for the severe symptoms of infection.

Generally, the more toxins released, the sicker a person will be. A fatal dose in humans is about 0.1 micrograms (μg) of toxin per kilogram of body weight. Death is most commonly the result of necrosis (tissue death) of the heart or liver.

Disease Transmission

Diphtheria is transmitted (spread) by coming into contact with respiratory droplets from an infected person, such as through coughing or sneezing. If the disease is cutaneous, it can be spread by coming into contact with fluids from the open sores.

Less commonly, diphtheria can be spread by touching an object contaminated with respiratory secretions (such as a doorknob or toy) and then touching your nose, mouth, or eyes. This is referred to as fomite transmission.

Respiratory diphtheria is more common during the winter and spring. It Is also more common in areas where there is a lack of sanitation and people live together in crowded spaces. Travelers to endemic areas (areas where a disease is common) are vulnerable to infection.

In most cases, diphtheria can only be spread by a person who is sick. Without treatment, that person is infectious for two to six weeks.

Asymptomatic carriers can also spread the infection. These are people who have been infected but show no signs of the disease. Asymptomatic carriers are usually those who have been vaccinated.

How Is Diphtheria Diagnosed?

If a person has symptoms of diphtheria, a healthcare provider will take a swab of their throat or skin lesion. The sample will be cultured in a lab to detect Corynebacterium diphtheria and the toxins it produces.

Other tests will be ordered to characterize the severity of the infection and check for possible complications. These include:

• Cardiac troponins, a blood test to check for heart damage
• Electrocardiogram (ECG) to evaluate the heart function
• Echocardiogram, an imaging technique used to visualize the heart
• Kidney function tests
• Liver function tests

Medical professionals need to contact the Centers for Disease Control and Prevention (CDC) if diphtheria is suspected as the CDC is the organization that supplies the diphtheria antitoxin.

How Diphtheria Is Treated

Diphtheria is treated with an antitoxin that helps neutralize diphtheria toxin. It is administered in a hospital by intravenous (IV) infusion. The person would need to be isolated from others to prevent the spread of infection.

In addition to the antitoxin, the antibiotics erythromycin or penicillin would be delivered intravenously. People who have trouble breathing may require intubation and a mechanical ventilator.

People who live with or have had close contact with someone who has diphtheria will also need treatment and isolation until two negative tests for diphtheria are received. This usually occurs 48 hours after receiving the diphtheria antitoxin and starting antibiotic treatment.

Diphtheria is a notifiable disease. This means that public health officials will contact you and ask questions to help determine how you got infected. They will also want to know who you were in contact with after the infection so that they can treated.

People who have recovered from diphtheria are required to get the diphtheria vaccine. Getting diphtheria doesn't protect you from infection for the rest of your life. Only diphtheria vaccination confers long-lasting immune protection.

Summary

Diphtheria is a vaccine-preventable bacterial infection that is rare in the developing world but can turn deadly in young children and older adults.

Symptoms include difficulty breathing and a thick, gray coating in the upper respiratory tract. Prompt treatment with a diphtheria antitoxin and a course of antibiotics can help clear the infection and avoid potentially serious complications like pneumonia, liver failure, and kidney failure.