Influenza viruses in Nigeria, 2009-2010: results from the first 17 months of a national influenza sentinel surveillance system

J Infect Dis. 2012 Dec 15:206 Suppl 1:S121-8. doi: 10.1093/infdis/jis584.


Background: Influenza surveillance data from tropical, sub-Saharan African countries are limited. To better understand the epidemiology of influenza, Nigeria initiated influenza surveillance in 2008.

Methods: Outpatients with influenza-like illness (ILI) and inpatients with severe acute respiratory illness (SARI) were enrolled at 4 sentinel facilities. Epidemiologic data were obtained, and respiratory specimens were tested for influenza viruses, using real-time reverse-transcription polymerase chain reaction assays.

Results: During April 2009-August 2010, 2841 patients were enrolled. Of 2803 specimens tested, 217 (7.7%) were positive for influenza viruses (167 [8%] were from subjects with ILI, 17 [5%] were from subjects with SARI, and 33 were from subjects with an unclassified condition). During the prepandemic period, subtype H3N2 (A[H3N2]) was the dominant circulating influenza A virus subtype; 2009 pandemic influenza A virus subtype H1N1 (A[H1N1]pdm09) replaced A(H3N2) as the dominant circulating virus during November 2009. Among persons with ILI, A(H1N1)pdm09 was most frequently found in children aged 5-17 years, whereas among subjects with SARI, it was most frequently found in persons aged ≥ 65 years. The percentage of specimens that tested positive for influenza viruses peaked at 18.9% in February 2010, and the majority were A(H1N1)pdm09.

Conclusions: Influenza viruses cause ILI and SARI in Nigeria. Data from additional years are needed to better understand the epidemiology and seasonality of influenza viruses in Nigeria.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Body Fluids / virology
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Influenza A virus / classification*
  • Influenza A virus / isolation & purification*
  • Influenza, Human / epidemiology*
  • Influenza, Human / virology*
  • Male
  • Middle Aged
  • Nigeria / epidemiology
  • Prevalence
  • Real-Time Polymerase Chain Reaction
  • Sentinel Surveillance
  • Young Adult