RATIONALE FOR SURVEILLANCE
Pertussis is a major cause of childhood morbidity and mortality. An estimated 45 million cases and 400 000 deaths occur every year; 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 vaccination on disease incidence, identify high risk areas and identify outbreaks.
RECOMMENDED CASE DEFINITION
Clinical case definition
A person with a cough lasting at least 2 weeks with at least one of the following:
• paroxysms (i.e. fits) of coughing
• inspiratory "whooping"
• post-tussive vomiting (i.e. vomiting immediately after coughing)
• without other apparent cause
Laboratory criteria for diagnosis
• Isolation of Bordetella pertussis, or
• Detection of genomic sequences by polymerase chain reaction (PCR)
Suspected: A case that meets the clinical case definition.
Confirmed: A person with a cough that is laboratory-confirmed.
RECOMMENDED TYPES OF SURVEILLANCE
Routine monthly reporting of aggregated data of suspected and confirmed cases from peripheral level to intermediate and central level. Zero reporting required at all levels.
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 (where DTP3 coverage is usually >80%), additional information of age group and immunization status should be collected. As an alternative, case-based surveillance, active surveillance, sentinel surveillance and/or occasional surveys and/or laboratory confirmation for suspected cases should be considered.
International: Aggregated data of clinical (suspected) and confirmed cases in routine surveillance reports of countries to WHO Regional Offices according to regional specifications.
RECOMMENDED MINIMUM DATA ELEMENTS
Aggregated data for reporting
• Number of cases
• Number of 3d doses of diphteria-pertussis-tetanus vaccine (DTP3) given to infants
• Completeness/timeliness of monthly reports
CASE-BASED DATA FOR INVESTIGATION AND REPORTING
• Unique identifier
• Geographical information (e.g., district and province)
• Date of birth
• Date of onset
• Total number of pertussis vaccine doses; 99 = unknown
• Date of latest pertussis vaccine dose; 99 = unknown
• Classification: 1 = confirmed: 2 = suspected; 3 = discarded
RECOMMENDED DATA ANALYSES, PRESENTATION, REPORTS
• Incidence rate by month, year, and geographic area
• DTP3 coverage by year and geographic area
• Completeness/timeliness of monthly reporting
• Proportional morbidity (compared to other diseases of public health importance)
Case-based data same as aggregated data plus the following
• Age-specific incidence rate
• Immunization status of cases
• Case-fatality rate
• Proportional mortality (compared to other diseases of public health importance)
PRINCIPAL USES OF DATA FOR DECISION-MAKING
• Investigate outbreaks to understand epidemiology of pertussis in the country, why the outbreak occurred (e.g., failure to immunize, vaccine failure, 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/supportive care, patients not seeking treatment in time)
• Determine age-specific incidence rate, and incidence rate by geographical area to know risk groups/areas
• Monitor incidence rate to assess impact of control efforts
See Regional Communicable Disease contacts on section "Communicable disease contacts in Regional Offices".
Headquarters: 20 Avenue Appia, CH-1211 Geneva 27, Switzerland
Vaccines and Other Biologicals (VAB)/Expanded Programme on Immunization (EPI)
E-mail: email@example.com / Surveillancekit@who.ch
Tel: (41 22) 791 4527/2111
Fax: 791 4193 attn EPI