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. 2013 May;7(3):304-11.
doi: 10.1111/j.1750-2659.2012.00394.x. Epub 2012 Jun 21.

Epidemiological and virological characteristics of seasonal and pandemic influenza in Lao PDR, 2008-2010

Bouaphanh Khamphaphongphane  1 , Pakapak Ketmayoon, Hannah C Lewis, Darouny Phonekeo, Thongchanh Sisouk, Sinakhone Xayadeth, Somvay Ongkhammy, Phengta Vongphrachanh, Reiko Tsuyuoka, Ann Moen, Andrew Corwin
Affiliations

Epidemiological and virological characteristics of seasonal and pandemic influenza in Lao PDR, 2008-2010

Bouaphanh Khamphaphongphane et al. Influenza Other Respir Viruses. 2013 May.

Abstract

Background: Information on influenza virology and epidemiology from Lao PDR is limited and the seasonal patterns of influenza have not been previously described.

Objectives: To describe epidemiological and virologic characteristics of influenza in Lao PDR to recommend public health interventions, including improvements in surveillance and response.

Patients/methods: We performed a descriptive analysis of samples taken from patients with influenza-like-illness (ILI) (fever >38°C with cough and/or sore throat) presenting at seven sentinel hospitals in three regions of Lao PDR, January 2008-December 2010. A nasopharyngeal (NP) swab or combined nasal with oropharyngeal swab was collected from patients with ILI. Samples were tested for influenza by either Luminex RVP, conventional reverse transcriptase PCR (RT-PCR) (January 2008-2009), or by real-time PCR (rRT-PCR) using US CDC reagents (February 2009 onward).

Results: Of 2346 samples tested from patients with ILI, 523 (22%) were positive for influenza. The median age of those positive was 12 years (range, <1-60 year). The percentage of samples that were influenza positive was similar over the 3 years (20-23%). Each year 3-4 types/subtypes cocirculated with differing predominant type/subtype. Influenza was detected year-round with the highest proportion of positive specimens in the 3rd and 4th quarter.

Conclusions: Similar to other countries in the region, we found that influenza is present year-round and has a peak activity from July to December. Dominant types or subtypes vary by year. A large proportion of patients with ILI are not influenza positive. ILI surveillance is critical for weighing disease burden, both morbidity and mortality, against the costs of advancing influenza vaccine delivery strategy.

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Figures

Figure 1
Figure 1
Patients meeting ILI case definition, three central hospitals in Vientiane Capital, 2008–2010. ILI, influenza‐like‐illness.
Figure 2
Figure 2
Age group of patients presenting to three central hospitals, Vientiane Capital, 2008–2010.
Figure 3
Figure 3
No. ILI specimens tested and proportion positive for influenza in Lao PDR, 2008–2010 (n = 2338). ILI, influenza‐like‐illness
Figure 4
Figure 4
Proportion of influenza subtypes by month in Lao PDR, 2008–2010 (n = 2338).
Figure 5
Figure 5
Number of specimens positive for influenza by subtype and week, Lao PDR, 2010 (n = 270).
See this image and copyright information in PMC

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