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. 2014 Jun 23;9(6):e98615.
doi: 10.1371/journal.pone.0098615. eCollection 2014.

Results from the first six years of national sentinel surveillance for influenza in Kenya, July 2007-June 2013

Mark A Katz  1 , Philip Muthoka  2 , Gideon O Emukule  1 , Rosalia Kalani  2 , Henry Njuguna  1 , Lilian W Waiboci  1 , Jamal A Ahmed  1 , Godfrey Bigogo  1 , Daniel R Feikin  1 , Moses K Njenga  1 , Robert F Breiman  1 , Joshua A Mott  1
Affiliations

Results from the first six years of national sentinel surveillance for influenza in Kenya, July 2007-June 2013

Mark A Katz et al. PLoS One. .

Abstract

Background: Recent studies have shown that influenza is associated with significant disease burden in many countries in the tropics, but until recently national surveillance for influenza was not conducted in most countries in Africa.

Methods: In 2007, the Kenyan Ministry of Health with technical support from the CDC-Kenya established a national sentinel surveillance system for influenza. At 11 hospitals, for every hospitalized patient with severe acute respiratory illness (SARI), and for the first three outpatients with influenza-like illness (ILI) per day, we collected both nasopharyngeal and oropharyngeal swabs. Beginning in 2008, we conducted in-hospital follow-up for SARI patients to determine outcome. Specimens were tested by real time RT-PCR for influenza A and B. Influenza A-positive specimens were subtyped for H1, H3, H5, and (beginning in May 2009) A(H1N1)pdm09.

Results: From July 1, 2007 through June 30, 2013, we collected specimens from 24,762 SARI and 14,013 ILI patients. For SARI and ILI case-patients, the median ages were 12 months and 16 months, respectively, and 44% and 47% were female. In all, 2,378 (9.6%) SARI cases and 2,041 (14.6%) ILI cases were positive for influenza viruses. Most influenza-associated SARI cases (58.6%) were in children <2 years old. Of all influenza-positive specimens, 78% were influenza A, 21% were influenza B, and 1% were influenza A/B coinfections. Influenza circulated in every month. In four of the six years influenza activity peaked during July-November. Of 9,419 SARI patients, 2.7% died; the median length of hospitalization was 4 days.

Conclusions: During six years of surveillance in Kenya, influenza was associated with nearly 10 percent of hospitalized SARI cases and one-sixth of outpatient ILI cases. Most influenza-associated SARI and ILI cases were in children <2 years old; interventions to reduce the burden of influenza, such as vaccine, could consider young children as a priority group.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Map of Kenya showing the distribution of influenza sentinel surveillance site.
Figure 2
Figure 2. Seasonality of influenza for ILI and SARI patients, Kenya, July 2007–June 2013.
Note: Smoothing done using the double exponential smoothing methods.
See this image and copyright information in PMC

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References

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Publication types

Grants and funding

The surveillance described in this manuscript was funded by a cooperative agreement between the US Centers for Disease Control and the Kenya Ministry of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.