Trends in performance of the national measles case-based surveillance system, Ministry of Health and Child Welfare, Zimbabwe (1999 - 2008)

Introduction: Since adoption of the measles case-based surveillance system in Zimbabwe in 1998, data has been routinely collected at all levels of the health delivery system and sent to national level with little or no documented evidence of use to identify risky populations, monitor impact of interventions and measure progress towards achieving measles elimination. We analysed this data to determine trends in the national measles case-based surveillance system (NMCBSS).

Methods: A retrospective record review of the NMCBSS dataset for period 1999 -2008 was conducted, assessing trends in proportions of investigated cases; timeliness and nature of specimens received at laboratory; timeliness of feedback of serology results, proportion of cases confirmed as measles and national annualized rates of investigation. Comparisons with WHO performance indicators were done. The secondary data analysis was done in Excel and Epi-Info statistical software.

Results: Cumulatively 4994 suspected cases were reported and investigated between 1999 and 2008. Reported suspected and confirmed measles cases declined from 24, 5% and 5.9% respectively in 2000 to 3.9% and 1.0% respectively in 2008. Proportion of cases with blood specimens collected and proportion reaching laboratory timely increased from 83% and 65% respectively in 1999, to 100% and 82% respectively in 2008. Proportion of specimens arriving at laboratory in good condition improved from 65% in 2004 to 94% in 2008 while timeliness of feedback of serology results improved from 4% in 2004 to 65% in 2008. Sensitivity of the NMCBSS however has been weakening, declining from 9.04 cases investigated per 100,000 population per year in 2000 to 1.58 cases/100,000/year in 2008.

Conclusion: The NMCBSS improved in quality, timeliness and feedback of laboratory results of specimens sent for investigation, but its sensitivity declined mainly due to reduced capacity to detect and confirm measles cases. We recommend training staff on active surveillance of cases and more support and supervisory visits to strengthen EPI surveillance.