Influenza sentinel surveillance in Rwanda, 2008-2010

Abstract

Background: In 2008, Rwanda established an influenza sentinel surveillance (ISS) system to describe the epidemiology of influenza and monitor for the emergence of novel influenza A viruses. We report surveillance results from August 2008 to July 2010.

Methods: We conducted ISS by monitoring patients with influenza-like illness (ILI) and severe acute respiratory infection (SARI) at 6 hospitals. For each case, demographic and clinical data, 1 nasopharyngeal specimen, and 1 oropharyngeal specimen were collected. Specimens were tested by real-time reverse-transcription polymerase chain reaction for influenza A and B viruses at the National Reference Laboratory in Rwanda.

Results: A total of 1916 cases (945 ILI and 971 SARI) were identified. Of these, 29.2% (n = 276) of ILI and 10.4% (n = 101) of SARI cases tested positive for influenza. Of the total influenza-positive cases (n = 377), 71.8% (n = 271) were A(H1N1) pdm09, 5.6% (n = 21) influenza A(H1), 7.7% (n = 29) influenza A(H3), 1.6% (n = 6) influenza A (unsubtyped), and 13.3% (n = 50) influenza B. The percentage of positivity for influenza viruses was highest in October-November and February-March, during peaks in rainfall.

Conclusions: The implementation of ISS enabled characterization of the epidemiology and seasonality of influenza in Rwanda for the first time. Future efforts should determine the population-based influenza burden to inform interventions such as targeted vaccination.