Controlling Spread of Diptheria

Table of Contents

A. Isolation and Quarantine Requirements

Minimum Period of Isolation of Patient

Maintain Droplet Precautions for respiratory diphtheria in healthcare facility or home until two successive pairs of nose and throat cultures obtained not <24 hours after completion of antimicrobial therapy and > 24 hours apart are negative. If cultures remain positive contact IDPH, CADE at (800) 362-2736 for further guidance. If there was no antimicrobial therapy, the two sequential pairs of cultures should be taken after symptoms resolve, and > 2 weeks after onset.  If cultures remain positive, contact IDPH, CADE at (800) 362-2736 for further guidance.

If an avirulent (nontoxigenic) strain is documented, isolation is not necessary.

Minimum Period of Quarantine of Contacts

Contacts whose occupations involve handling food or working with unimmunized children must be excluded from work until two successive pairs of nose and throat cultures, obtained not <24 hours after completion of antimicrobial therapy and > 24 hours apart, are negative. If cultures remain positive, contact IDPH, CADE at (800) 362-2736 for further guidance. These requirements may be extended to other contacts who work in high-risk settings, as determined by IDPH.

B. Protection of Contacts of a Case

Close contacts are defined as those who sleep in the same house or who share food, drink, or eating/drinking utensils with the case, or otherwise share saliva with case such as child care contacts, and healthcare workers in contact with the case’s oral or respiratory secretions. Those contacts that were in brief contact with the case, but do not meet the definition of a close contact, are not considered significant contacts. 

Below, management of cases and contacts is divided into four categories: 1) cases, 2) cases and symptomatic close contacts, 3) asymptomatic close contacts, and 4) nonsignificant contacts. It is important to follow the sequence of actions, as administration of antibiotics, diphtheria antitoxin (DAT), and diphtheria toxoids will interfere with interpretation of diagnostic testing. Attachment C (at the end of this chapter) presents these recommendations in diagram form.

1. Case(s)

Place cases of respiratory diphtheria in Droplet Precautions until two cultures from both the nose and the throat are negative for toxigenic C. diphtheriae. Material for these cultures should be obtained not <24 hours after completion of antimicrobial therapy and > 24 hours apart. If cultures remain positive, contact IDPH, CADE at (800) 362-2736 for further guidance.  If there was no antimicrobial therapy, the cultures should be taken after symptoms resolve, > 2 weeks after their onset, and > 24 hours apart. Continue as described in Section 2 immediately below.

2. Cases and Symptomatic Close Contacts

  1. Do not delay treatment to collect specimens.
  2. Collect cultures as described in Attachment A (located at the end of this chapter). If antibiotics have been started, it is useful to collect specimens for PCR and serology, which are described in Attachment B (at the end of this chapter). If possible, serology specimens should be collected before administration of diphtheria antitoxin (DAT) or diphtheria toxoid. 
  3. Treat with appropriate antibiotic, and evaluate cases and symptomatic close contacts for initiation of therapy with DAT. DAT can be obtained from CDC through an Investigational New Drug (IND) protocol. Healthcare providers treating a case of suspected diphtheria can contact IDPH, CADE at (800) 362-2736 for assistance in obtaining DAT.  Serology specimens should be collected before administration of DAT.
  4. If cases or symptomatic close contacts are culture-positive, they will need two repeat pairs of nose and throat cultures obtained not <24 hours after completion of antimicrobial therapy and > 24 hours apart. If cultures remain positive, contact IDPH, CADE at (800) 362-2736 for further guidance. If a case or symptomatic close contact has not received antibiotics, two successive pairs of nose and throat cultures taken after symptoms resolve, > 2 weeks after the onset of symptoms, and > 24 hours apart are needed. If cultures remain positive, contact IDPH, CADE at (800) 362-2736 for further guidance.
  5. Cases and symptomatic close contacts that are not up to date should be immunized with a diphtheria toxoid-containing preparation appropriate for age during convalescence. (Refer to Section 3) D for recommendations on completing the schedule).  Remember, serum should be collected before vaccinating. 
  6. Close contacts should be monitored for symptoms daily for at least 7 days after the last exposure. Active surveillance for suspect cases in affected settings should take place for at least two incubation periods (10 days).

3. Asymptomatic Close Contacts

  1. Where diphtheria is confirmed or highly suspected in the case, asymptomatic close contacts should be excluded from work if work involves food or unimmunized children.
  2. Where diphtheria is confirmed or highly suspected in the case, all asymptomatic close contacts should have cultures collected as described in Attachment A (at the end of this chapter).
  3. Assess and monitor for signs and symptoms of diphtheria for at least 7 days.
  4. Assess diphtheria toxoid vaccination status and vaccinate as outlined below:
  • If < 3 doses or unknown administer a dose of diphtheria toxoid (DTaP, DT, or Td as appropriate) and complete primary series according to schedule.
  • If > 3 doses and last dose were >5 years ago, administer a booster dose of diphtheria toxoid.
  • If > 3 doses and last dose was < 5 years ago, children needing their fourth primary dose or booster dose should be vaccinated; otherwise vaccination is not required.

All close contacts (regardless of culture result or immunization status) should begin antibiotic prophylaxis with oral erythromycin (40-50 mg/kg/day for 7 days, maximum 2 g/day, for children; and 1/g/day for adults.  A single IM dose of benzathine penicillin G (600,000 U for persons < 6 years of age and 1,200,000 U for persons > 6 years of age) is an alternative. (The lower dose of penicillin is for patients weighing less than 30 kg.)

  1. All asymptomatic close contacts who were initially culture-positive will need two repeat pairs of nose and throat cultures taken not < 24 hours after antibiotics have been discontinued and > 24 hours apart. If an asymptomatic contact has not received antibiotics, two successive pairs of nose and throat cultures taken > 24 hours apart are needed. If any of the repeat cultures is positive, an additional 10-day course of oral erythromycin should be given and the cultures repeated as described above.
  2. Close contacts should be monitored for symptoms daily for at least 7 days after their last exposure. Active surveillance for suspect cases in affected settings should be conducted for at least two incubation periods (10 days).

4. Non-Significant Contacts

Contacts who do not sleep in the same house as the case; do not share food, drink, or eating/drinking utensils with the case; and are not healthcare workers in contact with the case’s oral or respiratory secretions should be immunized with the appropriate diphtheria toxoid-containing preparation as described in Section 3) D above. They do not need to be cultured or placed on antibiotic prophylaxis.

C. Managing Special Situations

Reported Incidence Is Higher than Usual/Outbreak Suspected

Immunize the largest possible proportion of the population group involved, emphasizing protection of infants and preschool children.  In an epidemic involving adults, immunize groups that are most affected and at highest risk.  Repeat immunization procedures one month later to provide a second dose. 

D. Preventive Measures

Vaccination, including routine childhood vaccination and Td boosters beginning at age 11-12 years and continuing every 10 years thereafter, is the best preventive measure against diphtheria. Tetanus toxoid-containing formulations should always be used. The Advisory Committee on Immunization Practices (ACIP) recommends that all children receive a routine series of five doses of tetanus and diphtheria vaccine at ages 2, 4, 6, 15-18 months, and 4-6 years. Booster doses of diphtheria and tetanus toxoids should be administered beginning at age 11-12 years (provided at least 5 years have passed since the last dose) and every 10 years thereafter. DTaP should be used in persons < 7 years of age, whereas Td is the preferred preparation for persons > 7 years of age.

The Td schedule for those beginning immunization at ³ 7 years of age consists of 3 doses. The second dose is usually given 1-2 months after the 1st dose and the 3rd dose 6 months after the 2nd dose.

Due to the presence of diphtheria worldwide, it is important for all international travelers to be up to date with DTaP/DT/Td vaccination. Good personal hygiene (which consists of proper handwashing, disposal of used tissues, not sharing eating utensils) and avoiding sick people is important in prevention.

Iowa Dept. of Public Health, Revised  7/15