Emergencies preparedness, response

WHO Report on Global Surveillance of Epidemic-prone Infectious Diseases - Meningococcal disease

Description of the data

There are three types of data collected on meningococcal disease namely national data on the number of cases and deaths each year, weekly data on the number of cases and deaths in meningitis belt countries, and data on specific epidemics.

Annual national level data

The main function of this global database is to keep track of major epidemics of meningitis and major geographical trends over time. This database includes the number of cases per year per country, (both endemic and epidemic cases) and dates back to 1966. The database contains officially reported data as well as other published reports from countries when available. Twice a year, letters are sent to regional offices asking for data from countries to maintain this database.

Weekly national level data for meningitis belt countries

Since the end of 1997, WHO has been receiving weekly reports of the number of cases and deaths per country in the African meningitis belt during the meningitis season. Outside the meningitis season reporting is once every two weeks. This includes zero reporting (1).

Local level data on specific epidemics

Since 1992, WHO country offices, Médecins Sans Frontières, the United Nations Children's Fund, International Federation of Red Cross and Red Crescent Societies, and other non-governmental Organizations have been sending data to WHO on local outbreaks of meningococcal disease mainly to justify appeals for vaccination supplies. This data is often on district or county level, and sometimes includes age and sex breakdowns. Population data for calculating rates is sometimes available, especially for requests to the ICG. Supplementary information on specific outbreaks is available at WHO, but is not presented in this chapter.

Strengths and weaknesses of the data

Annual national level data
Since meningococcal disease is an epidemic disease with long cycles between epidemics, it is important to have data over a long period of time to be able to monitor major trends. The data presented here on the annual number of cases and deaths for each country has been collected for over 30 years and is an adequate time period for broadly monitoring major changes in epidemic patterns. Despite some incompleteness, the fact that the data were supplemented by official publications makes it unlikely that major outbreaks have been completely unreported. The data are relatively complete for the African and Eastern Mediterranean regions, but there are other parts of the world where data reporting is less complete. One reason for this is that in many countries meningococcal disease is relatively rare and not notifiable. Other reasons for non-reporting include a reluctance to report for economic reasons.

Weekly national level data for meningitis belt countries
These data provide more detailed information about the timing of the epidemics than the annual data; however, the data have only been collected for two years - so they provide a very short time series.

Case definitions
There are differences in the case definitions used for reporting; some countries report cases comprising both viral and bacterial meningitis, others report bacterial meningitis only; some countries only report laboratory confirmed cases whilst others also report suspected cases. These differences in reporting make it difficult to compare countries.

There are a number of aspects for surveillance which are missing from the data set. For example, it is difficult to trace the spread of different strains of meningococcal diseases because data on strains is not collected systematically. Likewise the data set is not comprehensive enough to study the effects of factors such as mass migration, climate, herd immunity, antimicrobial resistance and vaccination.

The weekly national level reporting for the meningitis belt in Africa, which has been going on for the last two years is a very promising development. The reporting system is more timely, and provides more detailed and more comparable data than previously available. It makes it possible to follow the control of an epidemic. This system needs to be continued, and further strengthened.

(1) Zero reporting means that if there are no cases during a particular period, instead of sending no report, a report is sent indicating that zero cases were identified.