Background: To assess the epidemiology and seasonality of influenza in Uganda, we established a sentinel surveillance system for influenza in 5 hospitals and 5 outpatient clinics in 4 geographically distinct regions, using standard case definitions for influenzalike illness (ILI) and severe acute respiratory illness (SARI).
Methods: Nasopharyngeal and oropharyngeal specimens were collected from April 2007 through September 2010 from patients with ILI and SARI aged ≥ 2 months, tested for influenza A and B with real-time reverse-transcription polymerase chain reaction, and subtyped for seasonal A/H1, A/H3, A/H5, and 2009 pandemic influenza A (pH1N1).
Results: Among the 2758 patients sampled, 2656 (96%) enrolled with ILI and 101 (4%) with SARI. Specimens from 359 (13.0%) were positive for influenza; 267 (74.4%) were influenza A, and 92 (25.6%) were influenza B. The median age of both patients with ILI and patients with SARI was 4 years (range, 2 months to 67 years); patients aged 5-14 years had the highest influenza-positive percentage (19.6%), and patients aged 0-4 years had the lowest percentage (9.1%). Influenza circulated throughout the year, but the percentage of influenza-positive specimens peaked during June-November, coinciding with the second rainy season.
Conclusions: Continued and increased surveillance is needed to better understand the morbidity and mortality of influenza in Uganda.