Rationale for surveillance
Recommended case definitions
Recommended surveillance measures
Recommended minimum data elements
Principal use of data for decision-making
Surveillance indicators

RATIONALE FOR SURVEILLANCE
Diphteria
Diphtheria is a highly contagious bacterial disease that is transmitted from person to person through close physical and respiratory contact. It can cause large epidemics in areas of low vaccination coverage. The control of diphtheria is based on the following measures: 1) primary disease prevention through maintenance of high vaccine coverage rates 2) prevention of secondary transmission through rapid identification and post-exposure treatment of close contacts and 3) prevention of complications and mortality by early diagnosis and proper disease management. Surveillance data can be used to monitor levels of coverage.

Pertussis
Pertussis (whooping cough) is a highly contagious acute bacterial disease involving the respiratory tract. It is transmitted by direct contact with discharges from the respiratory mucous membranes of infected persons by the airborne route. Worldwide, an estimated 20-40 million cases and 200,000 deaths occur annually. Case fatality rates in developing countries can reach 15%. High routine coverage with effective vaccine is the mainstay of prevention. Surveillance data on the disease can monitor the impact of immunization programs as well as identify high-risk areas, age groups for targeted immunization, and outbreaks.

RECOMMENDED CASE DEFINITIONS
Diphteria
Clinical case definition: An illness characterized by laryngitis or pharyngitis or tonsillitis and an adherent membrane of the tonsils, pharynx and/or nose with an average incubation period of 2-5 days.

Laboratory criteria: Isolation of bacterial agent Corynebacterium diphtheriae from a pharyngeal swab or a fourfold rise in serum antibody (only if both serum samples were obtained before the administration of diphtheria toxoid or antitoxin), or histopathologic diagnosis of diptheria.

Case classification:
Probable: A case that meets the clinical case definition.
Confirmed: A probable case that is laboratory confirmed or epidemiologically linked to a laboratory confirmed case.
Persons with positive C. diphtheriae cultures not meeting the clinical case definition (asymptomatic carriers or cutaneous diphtheria) should not be reported as probable or confirmed diphtheria cases. Respiratory disease caused by non-toxigenic C. diphtheriae should be reported as diphtheria.

Pertussis
Clinical case definition: A person with a cough lasting at least two weeks with at least one of the following:
1. Paroxysms (i.e. fits) of coughing
2. Inspiratory "whooping"
3. Post-tussive vomiting (i.e. vomiting immediately after fits of coughing) and without other apparent cause. ·

Laboratory criteria: Isolation of bacterial agent Bortadella pertussis or detection of genomic sequences by polymerase chain reaction (PCR).
*Direct fluorescent antibody (DFA) testing of nasopharyngeal secretions has been shown to have low sensitivity, and variable specificity, and should NOT be relied upon as a criterion for laboratory confirmation.

Case classification:
Suspected: A case that meets the clinical case definition.
Confirmed: A person with a cough that is laboratory-confirmed or epidemiologically linked to a laboratory confirmed case.

RECOMMENDED SURVEILLANCE MEASURES
Diphteria

• Routine weekly reporting of case-based data of suspected cases from municipalities to central level. Zero reporting should be required and validated.
• All outbreaks should be investigated immediately and laboratory confirmed; during an outbreak, case-based data should be collected.
• To describe the changing diphtheria epidemiology in countries with low diphtheria incidence (generally where coverage is > 80%), additional information on age group and immunization status should be collected.
• Feedback every month to all participants of the surveillance system is recommended.
  

Pertussis

• Routine monthly reporting of aggregated data of suspected cases from municipalities to central level. Zero reporting should be required and validated.
• All outbreaks should be investigated immediately and laboratory confirmed; during an outbreak, case-based data should be collected.
• To describe the changing pertussis epidemiology in countries with low pertussis incidence (generally where coverage is > 80%), additional information on age group and immunization status should be collected.
• Feedback every month to all participants of the surveillance system is recommended.
  

RECOMMENDED MINIMUM DATA ELEMENTS

Diphteria
Case-based data: (i) unique identifier (ii) date of birth (iii) geographic location (iv) date of onset of symptoms (v) date of first treatment (vi) laboratory results with information regarding toxigenicity (vii) treatment type, (viii) date of each DTP-containing shot received, (ix) date of last dose, (x) outcome (alive, dead, unknown), and (xi) case classification (probable, confirmed, discarded)

Pertussis
Aggregated data (monthly): (i) Number of confirmed cases; (ii) number of third doses of DTP-containing vaccine administered to infants (iii) completeness/ timeliness of monthly reporting

Case-based data: (i) unique identifier (ii) date of birth (iii) geographic location (iv) date of onset of symptoms (v) clinical symptoms (vi) laboratory results (vii) date of each DTP-containing shot received (viii) outcome (alive, dead, unknown) (ix) case classification (suspected, confirmed, discarded)

 

PRINCIPAL USE OF DATA FOR DECISION-MAKING

Diphteria

• · Detect and investigate outbreaks to understand the epidemiology of diphtheria in the country, why the outbreak occurred (e.g. failure to immunize, vaccine failure, and accumulation of susceptibles/ waning immunity, new toxigenic strain), ensure proper case management, and implement control measures.
• Monitor case fatality rate. If high, determine cause (e.g. poor case management, lack of antibiotics or antitoxin, patients not seeking timely treatment) so that corrective measures can be taken.
• Monitor incidence rate to assess impact of control efforts.
• Determine age-specific incidence rate, and incidence rate by geographical area to identify risk groups and temporal trends.
• Monitor immunization coverage per geographical area to identify areas of poor performance for special vaccination campaigns.

Pertussis

• Investigate outbreaks to understand the epidemiology of pertussis in the country, why the outbreak occurred (e.g. failure to immunize, vaccine failure, and accumulation of susceptibles/ waning immunity) and to ensure proper case management.
• Monitor case fatality rate. If high, determine cause (e.g. poor case management, lack of antibiotics or supportive care, patients not seeking timely treatment).
• Monitor incidence rate to assess impact of control efforts.
• Determine age-specific incidence rate, and incidence rate by geographical area to identify risk groups.
  

SURVEILLANCE INDICATORS

Diphteria

• % Of reporting sites that report each week.
• % Of reported suspected cases investigated within 3 days.
• % Of cases reported with complete vaccination history recorded.
• % Of persons with clinical symptoms that had laboratory confirmation.
• % Of total laboratory-confirmed cases with known source of infection.

Pertussis

• % of reporting sites that report each month.
• % Of reported suspected cases investigated within 3 days.
• % Of cases reported with complete vaccination history recorded.
• % Of persons with clinical symptoms that had laboratory confirmation.
• % Of total laboratory-confirmed cases with known source of infection.