Influenza activity in Cambodia during 2006-2008

Mardy, Sek; Ly, Sovann; Heng, Seng; Vong, Sirenda; Huch, Chea; Chea, Nora; Asgari, Nima; Miller, Megge; Bergeri, Isabelle; Rehmet, Sybille; Duong, Veasna; Zhou, Wen; Kasai, Takeshi; Touch, Sok; Buchy, Philippe

doi:10.1186/1471-2334-9-168

Cited by 41 publications

(64 citation statements)

References 16 publications

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“…Despite the annual presence of viruses, influenza viruses in Thailand annually presents two peaks, a major peak during the rainy season (June–August) and a minor peak in winter (October–February). Neighboring countries, such as Burma, Cambodia, Laos, and Vietnam, appear to have a similar peak of influenza viruses in the rainy season but the secondary peak was not as consistent 10 , 11 , 12 , 13 . Our study suggests that March and April may be the most appropriate months for seasonal influenza vaccination in Thailand.…”

Section: Discussionmentioning

confidence: 59%

Influenza viruses in Thailand: 7 years of sentinel surveillance data, 2004–2010

Chittaganpitch

Supawat

Olsen

et al. 2011

Influenza Resp Viruses

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Please cite this paper as: Chittaganpitch et al. (2012) Influenza viruses in Thailand: 7 years of sentinel surveillance data, 2004–2010. Influenza and Other Respiratory Viruses 6(4), 276–283. Background The re‐emergence of avian influenza A (H5N1) in 2004 and the pandemic of influenza A (H1N1) in 2009 highlight the need for routine surveillance systems to monitor influenza viruses, particularly in Southeast Asia where H5N1 is endemic in poultry. In 2004, the Thai National Institute of Health, in collaboration with the US Centers for Disease Control and Prevention, established influenza sentinel surveillance throughout Thailand. Objectives To review routine epidemiologic and virologic surveillance for influenza viruses for public health action. Methods Throat swabs from persons with influenza‐like illness and severe acute respiratory illness were collected at 11 sentinel sites during 2004–2010. Influenza viruses were identified using the standard protocol for polymerase chain reaction. Viruses were cultured and identified by immunofluorescence assay; strains were identified by hemagglutination inhibition assay. Data were analyzed to describe frequency, seasonality, and distribution of circulating strains. Results Of the 19 457 throat swabs, 3967 (20%) were positive for influenza viruses: 2663 (67%) were influenza A and able to be subtyped [21% H1N1, 25% H3N2, 21% pandemic (pdm) H1N1] and 1304 (33%) were influenza B. During 2009–2010, the surveillance system detected three waves of pdm H1N1. Influenza annually presents two peaks, a major peak during the rainy season (June–August) and a minor peak in winter (October–February). Conclusions These data suggest that March–April may be the most appropriate months for seasonal influenza vaccination in Thailand. This system provides a robust profile of the epidemiology of influenza viruses in Thailand and has proven useful for public health planning.

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Section: Discussionmentioning

confidence: 59%

Influenza viruses in Thailand: 7 years of sentinel surveillance data, 2004–2010

Chittaganpitch

Supawat

Olsen

et al. 2011

Influenza Resp Viruses

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“…In contrast, tropical countries in Asia below 11° N like Indonesia (Jakarta, 6.2° N), Malaysia (Kuala Lumpur, 3.2° N), and Singapore (1.3° N), influenza was found all throughout the year with no distinct influenza season [5]. Specific analysis on the association between influenza activity and climate variables has not been done in this study but June to November coincides with the rainy season in the Philippines similar to that of Cambodia [27], Myanmar [28], North Thailand [29], Bangladesh [5, 30], Lao [31], and some parts of India South of Srinagar [24, 25]. Factors other than the rainy season might also play a role for the increased influenza virus activity starting the month of June in the Philippines.…”

Section: Discussionmentioning

confidence: 99%

National Influenza Surveillance in the Philippines from 2006 to 2012: seasonality and circulating strains

et al. 2016

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BackgroundThe results of routine influenza surveillance in 13 regions in the Philippines from 2006 to 2012 are presented, describing the annual seasonal epidemics of confirmed influenza virus infection, seasonal and alert thresholds, epidemic curve, and circulating influenza strains.MethodsRetrospective analysis of Philippine influenza surveillance data from 2006 to 2012 was conducted to determine seasonality with the use of weekly influenza positivity rates and calculating epidemic curves and seasonal and alert thresholds using the World Health Organization (WHO) global epidemiological surveillance standards for influenza.ResultsIncreased weekly influenza positive rates were observed from June to November, coinciding with the rainy season and school opening. Two or more peaks of influenza activity were observed with different dominant influenza types associated with each peak. A-H1N1, A-H3N2, and two types of B viruses circulated during the influenza season in varying proportions every year. Increased influenza activity for 2012 occurred 8 weeks late in week 29, rather than the expected week of rise of cases in week 21 as depicted in the established average epidemic curve and seasonal threshold. The intensity was severe going above the alert threshold but of short duration. Southern Hemisphere vaccine strains matched circulating influenza virus for more surveillance years than Northern Hemisphere vaccine strains.ConclusionsInfluenza seasonality in the Philippines is from June to November. The ideal time to administer Southern Hemisphere influenza vaccine should be from April to May. With two lineages of influenza B circulating annually, quadrivalent vaccine might have more impact on influenza control than trivalent vaccine. Establishment of thresholds and average epidemic curve provide a tool for policy-makers to assess the intensity or severity of the current influenza epidemic even early in its course, to help plan more precisely resources necessary to control the outbreak. Influenza surveillance activities should be continued in the Philippines and funding for such activities should already be incorporated into the Philippine health budget.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-2087-9) contains supplementary material, which is available to authorized users.

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“…These findings are consistent with the reports from the countries. 13,[16][17][18][19][20][21][22][23][24][25][26][27] Host-related and environmental factors (e.g. lower temperatures and decreased humidity) may influence both viral transmission and host susceptibility.…”

Section: Discussionmentioning

confidence: 99%

“…14 FluNet data are regularly collected by surveillance systems in geographically disparate sentinel sites that register cases of influenza-like illness or severe acute respiratory infection. 13,[16][17][18][19][20][21][22][23][24][25][26][27] Data on specimen positivity and on viral subtypes were based upon specimens from these surveillance systems; all samples were tested using reverse transcription polymerase chain reaction assays, 28 with the exception of samples from India collected before 2009, which were tested with viral isolation methods. …”

Section: Data Collectionmentioning

confidence: 99%