Diphtheria
FAQs for Health Care Providers
Diphtheria Risk, Diagnosis, and Treatment in Afghan Evacuees
Diphtheria is a contagious acute bacterial (toxin strains of Corynebacterium diphtheriae) infection that can lead to respiratory or cutaneous diseases. It can quickly lead to respiratory failure due to swelling of the upper airway and asphyxia (from the pseudomembrane).
Have there been confirmed cases in the Afghan evacuees? No, although population is at risk.
Epidemiology
The incidence of diphtheria is very low worldwide (about 7 people for every 10,000,000), but the case fatality rate is ~10% (or 20% for the very young and very old). Unvaccinated people are at risk. According to the World Health Organization, Afghanistan had no reported cases in 2019-2020. Three cases were reported in 2018, and 1 in 2017. The last case reported before that was in 2007 when 104 were reported.
When should I consider diphtheria?
Clinical Presentation
Consider diphtheria in a person with a sore throat, swollen cervical lymph nodes, and a mild fever, especially if their vaccination status is unknown or not up to date. Your suspicion of diphtheria should increase if they report difficulty swallowing, changes in their voice, or if you notice stridor. The incubation stage is 10 days, so travel or potential exposure during this time period increases the likelihood.
The hallmark sign of diphtheria infection is a thick gray membrane in the back of the throat that develops by the third day of infection called a pseudomembrane that coats the upper airway and makes it very difficult for the person to breathe. If the pseudomembrane extends into the trachea or a piece becomes dislodged, this can be fatal.
Diphtheria can also present as open sores, ulcers, or a scaling rash on the skin or any mucous membrane (i.e. genitalia, ear, conjunctivae) which may also be contagious. The complications from the skin infection are less so than the respiratory infection.
Complications of diphtheria include respiratory compromise and asphyxiation, myocarditis, complete heart block, polyneuropathy, paralysis, renal failure, and death. Cutaneous diphtheria rarely results in complications.
Consider other mimics such as group A Streptococcus, mononucleosis, candidiasis, herpes infection, CMV, adenovirus, and HIV.
Is diphtheria contagious? Yes, very.
The R0 (number of cases per index case) is approximately 3 (measles >14, COVID19 <3). It can spread via respiratory droplets, contact with skin lesions, or with items that have discharge from the skin lesions.
Are there special infectious disease precautions for someone with diphtheria?
Given that diphtheria can manifest as both a respiratory infection and a cutaneous infection, precautions include contact (gloves, hand washing), and droplet (face mask) standard precautions. The disease is typically not contagious after 48 hours of antibiotic treatment, but it is advisable to maintain these precautions until the antibiotic course if negative and is culture-negative. Being culture-negative means obtaining two consecutive negative cultures 24 hours apart after antibiotic therapy is complete.
Patient should be isolated upon suspicion of diagnosis and infectious diseases on-call contacted. Diphtheria is a reportable disease, and any confirmed case must be reported to the Minnesota Department of Health.
How do I diagnose diphtheria?
Suspect respiratory diphtheria is a medically urgent case, especially if a membrane is noted in the pharynx. The patient should not be unduly stressed, and expert advice should be obtained (Infectious Diseases on-call). Diagnostic specimens can be delayed until acute stabilizing medical management is complete (e.g. securing a stable airway).
Diagnosis is confirmed by isolating C. diphtheriae, the causative bacteria, from culture obtained from nares, oropharynx, or any mucous or cutaneous lesion before antibiotics are initiated. It is best to obtain samples under the membrane or from the membrane itself. Then the organism should be tested for toxin production with the Elek test, an immunoprecipitation assay. CDC’s Pertussis and Diphtheria Laboratory is currently the only laboratory in the U.S. that performs the Elek test; therefore, isolates and specimens must be submitted to the CDC for testing.
What is the treatment for diphtheria?
All patients with respiratory diphtheria should be admitted to the hospital with appropriate contact and droplet precautions. The drug of choice is azithromycin, erythromycin, or penicillin for both respiratory and cutaneous diphtheria for 14 days. Treatment should be initiated based on suspicion of diphtheria and should not wait on diagnostic confirmation. Dosing is as follows:
Azithromycin PO
Children - 10-12 mg/kg daily
Adults – 500 mg daily
Erythromycin PO
Children under 40kg – 10-15 mg/kg 4x/day
Children 40kg and over, adults – 500 mg 4x/day
Penicillin V PO
Children under 40kg – 10-15 mg/kg 4x/day
Children 40kg and over, adults – 500 mg 4x/day
Procaine Benzylpenicillin IV
Children under 25 kg: 50 000 IU/kg (= 50 mg/kg) once daily (max. 1.2 MIU = 1.2 g daily)
Children 25 kg and over and adults: 1.2 MIU (= 1.2 g) once daily
Depending on the patient’s clinical status and medical resources, intubation may be necessary to secure the airway.
Diphtheria anti-toxin (DAT) should also be considered for all patients with suspected or confirmed respiratory Diphtheria infection. Experts should be consulted and a requested made first by speaking with the Minnesota Department of Health, and then calling the CDC at 770-488-7100 to request DAT. In patients with asthma, there is a risk of anaphylaxis.
After an infection with diphtheria, immunity is not always conferred, and vaccination is still suggested.
Information on managing exposures and preventive measures can be found here.
Resources and References
Contributors
Andrew Wu, MD
Cindy Howard, MD
William Stauffer MD
FAQs Diphtheria.pdf