Establishing seasonal and alert influenza thresholds in Cambodia using the WHO method: implications for effective utilization of influenza surveillance in the tropics and subtropics

Ly, Sovann, Arashiro, Takeshi, Ieng, Vanra, Tsuyuoka, Reiko, Parry, Amy, Horwood, Paul, Heng, Seng, Hamid, Sarah, Vandemaele, Katelijn, Chin, Savuth, Sar, Borann, and Arima, Yuzo (2017) Establishing seasonal and alert influenza thresholds in Cambodia using the WHO method: implications for effective utilization of influenza surveillance in the tropics and subtropics. Western Pacific Surveillance and Response, 8 (1). pp. 1-12.

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Objective: To establish seasonal and alert thresholds and transmission intensity categories for influenza to provide timely triggers for preventive measures or upscaling control measures in Cambodia.

Methods: Using Cambodia's influenza-like illness (ILI) and laboratory-confirmed influenza surveillance data from 2009 to 2015, three parameters were assessed to monitor influenza activity: the proportion of ILI patients among all outpatients, proportion of ILI samples positive for influenza and the product of the two. With these parameters, four threshold levels (seasonal, moderate, high and alert) were established and transmission intensity was categorized based on a World Health Organization alignment method. Parameters were compared against their respective thresholds.

Results: Distinct seasonality was observed using the two parameters that incorporated laboratory data. Thresholds established using the composite parameter, combining syndromic and laboratory data, had the least number of false alarms in declaring season onset and were most useful in monitoring intensity. Unlike in temperate regions, the syndromic parameter was less useful in monitoring influenza activity or for setting thresholds.

Conclusion: Influenza thresholds based on appropriate parameters have the potential to provide timely triggers for public health measures in a tropical country where monitoring and assessing influenza activity has been challenging. Based on these findings, the Ministry of Health plans to raise general awareness regarding influenza among the medical community and the general public. Our findings have important implications for countries in the tropics/subtropics and in resource-limited settings, and categorized transmission intensity can be used to assess severity of potential pandemic influenza as well as seasonal influenza.

Item ID: 48001
Item Type: Article (Research - C1)
ISSN: 2094-7313
Additional Information:

The articles in this publication are published by the World Health Organization and contain contributions by individual authors. The articles are available under the Creative Commons Attribution 3.0 IGO license (CC BY 3.0 IGO, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. In any use of these articles, there should be no suggestion that WHO endorses any specific organization, products or services. The use of the WHO logo is not permitted.

Date Deposited: 31 Mar 2017 05:37
FoR Codes: 32 BIOMEDICAL AND CLINICAL SCIENCES > 3202 Clinical sciences > 320211 Infectious diseases @ 100%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920109 Infectious Diseases @ 100%
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