Assessment of routine surveillance data as a tool to investigate measles outbreaks in Mozambique

Abstract

Background: Measles remains a major public health problem in Mozambique despite significant efforts to control the disease. Currently, health authorities base their outbreak control on data from the routine surveillance system while vaccine coverage and efficacy are calculated based on mathematical projections of the target population. The aim of this work was to assess the quality of the measles reporting system during two outbreaks that occurred in Maputo City (1998) and in Manica Province (2002).

Methods: Retrospectively, we collected data from the routine surveillance system, i.e. register books at health facilities and weekly provincial and national epidemiological reports. To test whether the provinces registered an outbreak, the distribution of measles cases was compared to an endemic level established based on cases reported in previous years.

Results: There was a significant under-notification of measles cases from the health facilities to the province and national level. Register books, the primary sources of information for the measles surveillance system, were found to be incomplete for two main variables: "age" and "vaccination status".

Conclusion: The Mozambican surveillance system is based on poor quality records, receives the notification of only a fraction of the total number of measles in the country and may result in failures do detect epidemics. The measles reporting system does not provide the data needed by Expanded Program on Immunisation managers to make evidence-based decisions, nor does it allow in-depth analysis to monitor measles epidemiology in the country. The progress of Mozambique to the next stage of measles elimination will require an improvement of the routine surveillance system and a stronger Health Information System.

Figure 1

The flow of disease surveillance information in the health system in Mozambique. Register books at health facilities serve as the primary epidemiological data source. Data from these is collected and sent in a weekly epidemiological bulletin (BES) format to the district health authorities. Districts compile data from all health facilities and report to provinces using a district BES. Provinces compile data from all its districts and report to the national authorities using a province BES. For the sake of simplicity, only one province is shown. The national authorities collect data from all provinces and produce a national BES.

Figure 2

Cases of measles during an outbreak in the year of 1998 in Maputo City. The continuous bold line represents the reported cases of measles in 1998. The grey line represents the geometric mean of reported measles cases for the years 1992–1997. The lines with squares represent the upper and lower endemic ranges.

Figure 3

Cases of measles during an outbreak in the year of 2002 in the Manica district of the Manica Province. The continuous bold line represents the reported cases of measles in 2002. The grey line represents the geometric mean of reported measles cases for the years 1991–2001. The lines with squares represent the upper and lower endemic ranges.

Figure 4

Cases of measles during an outbreak in the year of 2002 in the Gondola district of the Manica Province. The continuous bold line represents reported cases of measles in 2002. The grey line represents the geometric mean of reported measles cases for the years 1991–2001. The lines with squares represent the upper and lower endemic ranges.