-from Epidemiological Bulletin, Vol. 22 No. 4, December 2001-
Rationale for Surveillance
Meningococcal disease occurs sporadically and in epidemics of meningococcal
meningitis; the majority of cases occur in children <5 years. Meningococcal
meningitis is the only form of meningitis to cause epidemics. The case-fatality
rate is between 5% and 15%. While sub-Saharan Africa is the most severely affected
area, epidemic meningococcal disease can affect any country. Meningococcal bivalent
A, C and quadrivalent A, C, Y, W135 vaccines are available; immunization of
the entire population should be considered to halt epidemics due to A and C
serogroup meningocci. In some countries, vaccine is used for close contacts
of patients with meningococcal disease due to A, C, Y or W135 serogroups in
order to prevent secondary cases. Immunization is also indicated for people
travelling to endemic areas. Surveillance is needed to measure and detect epidemics
and establish the impact of both epidemic and non-epidemic disease.
Recommended Case Definition
Clinical case definition
An illness with sudden onset of fever (>38.5°C rectal or >38.0°C axillary)
and one or more of the following: neck stiffness, altered consciousness, other
meningeal sign or petechial or purpural rash
In patients <1 year, suspect meningitis when fever accompanied by bulging fontanelle.
Laboratory criteria for diagnosis
Positive CSF antigen detection or Positive culture.
Case classification
Suspected: A case that meets the clinical case definition.
Probable: A suspected case as defined above and turbid CSF (with
or without positive Gram stain) or ongoing epidemic and epidemiological link
to a confirmed case
Confirmed: A suspected or probable case with laboratory confirmation.
Recommended Types of Surveillance
At peripheral level, individual patient records should be maintained (particularly
for contact tracing).
Immediate reporting of all suspected or probable cases from peripheral level
to intermediate level.
All cases must be investigated.
Follow-up data on the organism identified and on patient outcome to be sought
by the intermediate level.
Routine weekly / monthly reporting of aggregated or case-based data, from intermediate
to central level.
A parallel surveillance using reference laboratories for meningococcal diseases
may provide detailed microbiological data on serogroup and genotype on a central
basis (useful for epidemiological analysis).
Note 1: In countries with limited surveillance infrastructure, 2 approaches to clinical surveillance can be integrated: 1. A limited amount of data reported from all health sites (e.g., new cases and deaths by week) 2. More extensive data reported from selected referral health centres.
Note 2: Surveillance of vaccine coverage may be undertaken in areas of mass vaccination or where vaccination for meningococcal disease is part of routine vaccination.
Recommended Minimum Data Elements
Clinical surveillance
Case-based data for individual patient records and for reporting:
Case classification (suspected / probable / confirmed), unique identifier, age,
sex, geographical information, date of onset, date of consultation, vaccination
status, treatment received, history of contact with a case, close contacts.
Aggregated data for reporting:
By case classification (suspected / probable / confirmed), age group, week,
geographical area, and outcome.
Laboratory Surveillance
Isolate-based data for reporting:
Unique identifier, age, sex, date of onset, date of specimen, specimen type,
serogroup.
Genotype.
Aggregated data for reporting:
Cases by age group, specimen type, serogroup, genotype.
Recommended Data Analyses, Presentation, Reports
- Incidence by week, month, geographical area and age group
- Use of incidence data to set epidemic thresholds by comparing weekly incidence
rates during the same period in 3-5 previous non-epidemic years (flagging)
- Distribution by serogroup and genotype (if available)
- Vaccine coverage (if available).
Principal Uses of Data for Decision-making
- Detect and control epidemics of meningococcal disease as early as possible,
especially in areas such as developing countries where epidemic meningitis raises
particular difficulties.
- Strengthen capacity for emergency response to epidemics of meningococcal disease.
- Mobilize immunization activities.
- Monitor immunization coverage by geographical area to monitor progress and
identify areas of poor performance.
- Monitor impact of vaccination on disease incidence and vaccine efficacy during
epidemics.
Special Aspects
Deciding when an epidemic is occurring or likely to occur (setting thresholds)
Hyperendemic areas: 15 cases per 100 000 per week averaged over 2 consecutive
weeks. Once epidemic disease is detected in a given area, a lower value (say
5 cases/100 000 per week) may be used as a threshold in contiguous areas.
Other situations: 3 to 4-fold increase compared with corresponding time
period in previous years, or Doubling of cases from one week to the next over
a period of 3 weeks.
Rationale for Surveillance
Viral meningitis occurs sporadically and also as an epidemic disease. Case-fatality
rates are generally low; infection may have potential long-term sequelae in
those affected (mostly children), but the disease is rarely severe and recovery
is usually complete. The early detection of epidemics through epidemiological
surveillance allows for identification of the causal agent and the institution
of targeted control measures and effective case management.
Recommended Case Definition
Clinical case definition
A case with fever =38.5°C and one or more of the following: neck stiffness,
severe unexplained headache, neck pain and 2 or more of the following
- photophobia
- nausea
- vomiting
- abdominal pain
- pharyngitis with exudates.
For children <2 years of age a case is defined as a case with fever =38.5°C and one or more of the following: irritability, bulging fontanelle.
Laboratory criteria for confirmation
The specific virus confirmed on cell culture.
Case classification
Suspected: A case that meets the clinical case definition.
Probable: A suspected case with one or more of the following:
- normal CSF glucose and normal or mild increase in CSF protein (>50mg/dl),
moderate increase CSF cells (<500/mm3) and lymphocyte predominance (>50%)
- CSF Positive for viral genomic sequences using PCR (Polymerase Chain Reaction)
- Epidemiological link to a confirmed case.
Confirmed: A suspected or probable case with laboratory confirmation.
Recommended Types of Surveillance
- At peripheral level individual patient records should be maintained.
- Immediate reporting of all suspected or probable cases from peripheral level
to intermediate level and central level.
- All cases must be investigated. Follow-up data on identified organism and
patient outcome to be sought by the intermediate and central level.
- Routine weekly reporting of aggregated or case-based data from intermediate
to central level.
A parallel surveillance using reference laboratories for viral diseases may provide more detailed virological data on specific causal agents on a national basis; these are very useful for epidemiological analysis.
Recommended Minimum Data Elements
Clinical Surveillance
Case-based data for individual patient record and for reporting: Case
classification (suspected / probable / confirmed), unique identifier, age, sex,
geographical information, date of onset, date of consultation, treatment received.
Aggregated data for reporting: Case by case classification (suspected / probable / confirmed), age group, week, geographical area, and outcome.
Laboratory Surveillance
Isolate-based data for reporting: Unique identifier, age, sex, date of
onset, date of specimen, specimen type, organism identified.
Aggregated data for reporting: Cases by age group, specimen type, organism identified.
Recommended Data Analyses, Presentation, Reports
Incidence by week, month, geographical area, age group, outcome.
Principal Uses of Data for Decision-making:
- To detect and control epidemics of viral meningitis as early as possible
- To strengthen the capacity for emergency response to epidemics of viral meningitis.
Return to Index
Epidemiological
Bulletin, Vol. 22 No. 4, December 2001