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. 2024 Aug;18(8):e13353.
doi: 10.1111/irv.13353.

Epidemiologic and Virologic Characteristics of Influenza in Lao PDR, 2016-2023

Natalie Wodniak  1 , KeoOudomphone Vilivong  2 , Bouaphanh Khamphaphongphane  2 , Bounthanom Sengkeopraseuth  2 , Virasack Somoulay  2 , May Chiew  3 , Pakapak Ketmayoon  3 , Melissa Jiao  3 , Sonesavanh Phimmasine  3 , Kim Carmela Co  3 , Phetdavanh Leuangvilay  3 , Satoko Otsu  3 , Viengphone Khanthamaly  4   5 , Phayvanh Keopaseuth  6 , William W Davis  1   5 , Martha P Montgomery  1   5 , Phonepadith Xangsayyarath  2
Affiliations

Epidemiologic and Virologic Characteristics of Influenza in Lao PDR, 2016-2023

Natalie Wodniak et al. Influenza Other Respir Viruses. 2024 Aug.

Abstract

Background: Influenza sentinel surveillance in Lao PDR is used to inform seasonal vaccination programs. This analysis reviews epidemiologic and virologic characteristics of influenza virus infection over 8 years, before and after emergence of SARS-CoV-2.

Methods: Data collected for ILI and SARI surveillance during January 2016 through December 2023 were analyzed from nine hospitals. Respiratory specimens from ILI and SARI cases were tested by reverse transcriptase polymerase chain reaction to determine influenza positivity and subtype and lineage. Aggregate counts of outpatient visits and hospitalizations were collected from hospital logbooks. Epidemiologic trends of influenza activity were described, and the proportional contribution of influenza-associated ILI and SARI to outpatient and inpatient loads was estimated.

Results: Influenza was detected year-round with positivity peaking during September through January and occurring in most years approximately 1 month earlier in the south than the north. After decreasing in 2 years following the emergence of SARS-CoV-2, influenza positivity increased in 2022 and resumed its typical temporal trend. Influenza-associated ILI contribution to outpatient visits was highest among children ages 5-14 years (3.0% of all outpatient visits in 2023), and influenza-associated SARI contribution to inpatient hospitalizations was highest among children ages 2-4 years (2.2% of all hospitalizations in 2023).

Conclusions: Influenza surveillance in Lao PDR provides clinicians and public health authorities with information on geographic and temporal patterns of influenza transmission. Influenza surveillance data support current vaccination timing and recommendations to vaccinate certain populations, especially young children.

Keywords: epidemiology; hospitalization; human influenza; reverse transcriptase polymerase chain reaction; sentinel surveillance; vaccination.

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Conflict of interest statement

The findings and conclusions in this article are those of the authors and do not necessarily represent the official position of the U.S. Centers for Disease Control and Prevention (CDC).

May Chiew, Pakapak Ketmayoon, Melissa Jiao, Sonesavanh Phimmasine, Kim Carmela Co, Phetdavanh Leuangvilay, and Satoko Otsu reported receiving financial support from U.S. Centers for Disease Control and Prevention and U.S. Defense Threat Reduction Agency for attending meetings and for official travel.

Figures

FIGURE 1
FIGURE 1
Location of influenza sentinel surveillance sites in Lao PDR, 2016–2023. Abbreviations: ILI, influenza‐like illness; PDR, People's Democratic Republic; SARI, severe acute respiratory illness.
FIGURE 2
FIGURE 2
Weekly percent positivity for influenza (top) and number of ILI and SARI specimens tested for influenza (bottom), Lao PDR 2016–2023. Abbreviations: PDR, People's Democratic Republic.
FIGURE 3
FIGURE 3
Proportion of influenza subtypes detected by month, Lao PDR 2016–2023. Abbreviations: PDR, People's Democratic Republic.
FIGURE 4
FIGURE 4
Proportional contributions of influenza‐associated ILI and SARI to hospital loads at nine sentinel sites, Lao PDR 2019–2023. ILI, influenza‐like illness; PDR, People's Democratic Republic; SARI, severe acute respiratory illness.
See this image and copyright information in PMC

References

    1. El Guerche‐Séblain C., Caini S., Paget J., Vanhems P., and Schellevis F., “Epidemiology and Timing of Seasonal Influenza Epidemics in the Asia‐Pacific Region, 2010–2017: Implications for Influenza Vaccination Programs,” BMC Public Health 19, no. 1 (2019): 331. - PMC - PubMed
    1. Western Pacific Region Global Influenza Surveillance and Response System , “Epidemiological and Virological Characteristics of Influenza in the Western Pacific Region of the World Health Organization, 2006‐2010,” PLoS ONE 7, no. 5 (2012): e37568. - PMC - PubMed
    1. Young B. E. and Chen M., “Influenza in Temperate and Tropical Asia: A Review of Epidemiology and Vaccinology,” Human Vaccines & Immunotherapeutics 16, no. 7 (2020): 1659–1667. - PMC - PubMed
    1. Cowling B. J., Caini S., Chotpitayasunondh T., et al., “Influenza in the Asia‐Pacific Region: Findings and Recommendations From the Global Influenza Initiative,” Vaccine 35, no. 6 (2017): 856–864. - PubMed
    1. Saha S., Chadha M., Al Mamun A., et al., “Influenza Seasonality and Vaccination Timing in Tropical and Subtropical Areas of Southern and South‐Eastern Asia,” Bulletin of the World Health Organization 92, no. 5 (2014): 318–330. - PMC - PubMed

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