Basic Information on Diphtheria

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Diphtheria is a common infectious disease.

Infectious agent:
Bacterium: Corynebacterium diphtheriae

Mode of transmission:
Contact (usually direct, rarely indirect) with the respiratory droplets of a case or carrier; or in rare cases, the disease may be transmitted though foodstuffs (raw milk has served as a vehicle).

Incubation period:
Usually 2-5 days, occasionally longer.
Image courtesy of CDC/ Graham Heid

Case Definition:

Probable case:

An acute illness characterized by an adherent membrane on the tonsils, pharynx and/or nose and any one of the following: laryngitis, pharyngitis or tonsillitis.

Confirmed case:

A confirmed case is a probable case who has been laboratory confirmed or linked epidemiologically to a laboratory confirmed case. At least one of the following criteria is used for diagnosing a confirmed case:

  • The isolation of Corynebacterium diphtheriae from a clinical specimen; or
  • A four fold or greater rise in serum antibody (but only if both serum samples were obtained before the administration of diphtheria toxoid or antitoxin).

Note that asymptomatic persons with positive C. diphtheriae cultures (i.e. asymptomatic carriers) should not be reported as probable or confirmed diphtheria cases.

Case Management:

For Patients:

Do not wait for laboratory results before starting treatment/ control activities.

Diphtheria antitoxin I/M (20 000 to 100 000 units) in a single dose, immediately after throat swabs have been taken; plus Procaine penicillin G I/M (25 000 to 50 000 units/kg/day for children; 1 200 000 units/kg/day for adults in 2 divided doses) or parenteral erythromycin (40-50 mg/kg/d with a maximum of 2 g/d) until the patient can swallow; then;

Oral penicillin V (125-250 mg) in 4 doses a day, or erythromycin (40-50 mg/kg/day) in divided doses. Antibiotic treatment should be continued for total of 14 days.

Note: Clinical diphtheria does not necessarily confer natural immunity, and patients should thus be vaccinated before discharge from a health facility with either primary or booster doses.

For Contacts:

All close contacts, regardless of vaccination status, should have nose and throat cultures, receive a single dose of benzathine penicillin I/M (600 000 units for children < 6; 1.2 million units for 6 or older) or a 7-10 day course of erythromycin (PO), and remain under surveillance for 7 days. Those who handle milk or work with school children should remain at home until culture results are available. If culture is positive, give antibiotics as for patients above.

Prevention and control:

  • Give priority to immunization of population at risk in areas not yet affected where the outbreak is likely to spread. Repeat immunization one month later to provide at least 2 doses to recipients.
  • Vaccine containing diphtheria toxoid (preferably Td – tetanus-diphtheria) should be given.
  • To ensure safety of injection during immunization, employ proper techniques, use auto destroyable syringes and safety boxes for safe disposal of used sharps.
  • Vaccination consists of DPT 3 doses of 0.5 ml each/IM administered to the children less than one year of age according to the following schedule: 1st dose at age six weeks; 2nd dose at age ten weeks; 3rd dose at age fourteen weeks.