9.12. Diphtheria

Standard Operating Procedure for the Surveillance of Diphtheria

Effective Date: [Date]

Version: 1.0

Prepared by: [Name/Department]

Approved by: [Name/Department]

Introduction

Purpose

The purpose of this SOP is to provide a comprehensive guide for healthcare providers, public health officials, and relevant stakeholders in the surveillance of Diphtheria.

Scope

This SOP applies to all healthcare facilities, public health departments, and vaccination centers involved in the administration of vaccines, the monitoring of VPDs, and the management of vaccine-related activities. 

DIPHTHERIA

Overview

Diphtheria is an acute bacterial disease of the upper respiratory tract and occasionally of the skin, conjunctivae or genitalia. It is caused by toxigenic strains of Corynebacterium diphtheriae. Infection may be clinically inapparent or may result in a mild nasal discharge in adults or severe laryngeal disease in children characterized by a greyish membrane caused by the bacterial cytotoxin.

Humans are the reservoir for C. diphtheria and transmission is by respiratory droplets, contact with nasopharyngeal secretions, infected skin lesions and rarely fomites. Persons may become asymptomatic carriers and can spread the disease to others. The disease can occur in epidemic proportions in any community with low immunization coverage. The incubation period is 2 to 5 days. The case fatality rate in recent outbreaks has been 5 to 10%.

Clinical presentation

There is usually an insidious onset of pharyngitis and/or laryngitis with a distinctive thick, adherent, greyish white membrane on the pharynx caused by the bacterial cytotoxin. Other mucous membranes may be affected. Patients may have enlarged anterior cervical lymph nodes, and oedematous surrounding tissue. 

On the skin lesions usually arise on exposed areas, especially on the legs. They appear as vesicles and quickly progress to small, sometimes multiple, well delineated, ulcers. Generally, disease of the skin is not accompanied by systemic symptoms.

Diphtheria vaccine is included in the childhood immunization schedule as part of the triple vaccine DTP - Diphtheria, Tetanus and Pertussis. Four doses constitute the primary series: the first at 6 - 8 weeks, the second and third at intervals of 4 - 8 weeks thereafter, and a booster at 18 months. The toxoid contained in this vaccine induces a long-lasting immunity.

The purpose of surveillance is to predict epidemics by early detection of cases so that control measures can be instituted, and to monitor the effectiveness of vaccination.

SURVEILLANCE PROCEDURES: 

Step 1: Case Detection and Reporting – Healthcare Providers / Laboratory Personnel 

Immediately report all suspected cases. Reports should be shared with laboratory personnel for confirmation. 

Case Definition

Probable Case: An illness characterized by tonsillitis or pharyngitis or laryngitis, and an adherent greyish membrane on the tonsils, pharynx and/or nose.

Confirmed case

Laboratory confirmed case

A probable case from which toxin-producing C. diphtheriae has been cultured, or a four-fold or greater rise in serum antibody (only if both serum samples are taken before the administration of diphtheria toxoid or antitoxin).

Epidemiologically confirmed case

A probable case that is linked epidemiologically to a laboratory confirmed case.

Laboratory Diagnosis

Laboratory Confirmation

Organisms are cultured and identified as C. diphtheriae toxigenic (which is diagnostic) or non-toxigenic.

Laboratory investigation of sporadic cases is necessary to rule out viral or streptococcal pharyngitis, Vincent’s angina, infectious mononucleosis, oral candidiasis or oral syphilis.

Specimen Collection and Transport

Throat, nose and/or nasopharyngeal swabs: These are collected from probable cases and placed in Amies transport medium. Nasopharyngeal and throat swabs are collected from healthy persons who are potential carriers. 

Specimens are transported at ambient temperature accompanied by a request form stating the site of the swab, age of the patient and clinical information.

Control and Prevention

Investigation

• Identify close contacts (household members, kissing, mouth-to-mouth resuscitation, health care worker providing care, child care centre, school setting).  Persons at risk are those with close contact with a case within the previous 7 days. 
• Identify the risk of exposure to potential sources of infection. 
• Obtain a travel history.
• Contacts of laboratory confirmed cases (regardless of their immunisation status) should have the following done:
  • Nose and throat cultures  
  • Wounds swabbed, 
  • Promptly receive antimicrobial prophylaxis. 
• Contacts should be monitored daily for 7 days for evidence of disease.

A threatened outbreak can be controlled by the following measures:

• Isolate pharyngeal patients and prevent contact with cutaneous cases.
• Treat promptly with antibiotics (penicillin or erythromycin).
• Culture contacts and administer chemoprophylaxis if found to be carriers.
• Conduct mass immunization in high risk populations, especially children.

Long term measures include:

• Education of parents on the necessity for completing the full schedule of infant immunization.
• Filling in of immunity gaps in any age group using DT or Td vaccine.
• Immunization of those at special risk, e.g. health care workers, and administration of 10-year booster doses. (Note: HIV positive children may be immunized

 Technical Notes

• It should also be noted that vaccination does not eliminate the carriage of C. diphtheriae in the pharynx, nose, or on the skin.
• Asymptomatic carriers should not be reported as probable or confirmed cases.
• Cases of cutaneous diphtheria should not be reported.