Circulation and characterization of seasonal influenza viruses in Cambodia, 2012‐2015

Paul F. Horwood (1, 2) , Erik A. Karlsson (1) , Srey Viseth Horm (1) , Sovann Ly (3) , Seng Heng (3) , Savuth Chin (4) , Chau Darapheak (4) , David Saunders (5) , Lon Chanthap (5) , Sareth Rith (1) , Phalla Y (1) , Kim Lay Chea (1) , Borann Sar (6) , Amy Parry (7) , Vanra Ieng (7) , Reiko Tsuyouka (7) , Yi-Mo Deng (8) , Aeron C. Hurt (8) , Ian G. Barr (8) , Naomi Komadina (8, 9) , Philippe Buchy (1, 10) , Philippe Dussart (1)

1 Unité de Virologie / Virology Unit [Phnom Penh]
2 JCU - James Cook University
3 Ministry of Health [Phnom Penh]
4 National Institute of Public Health [Phnom Penh, Cambodge]
5 AFRIMS - Armed Forces Research Institute of Medical Sciences [Bangkok]
6 Centers for Disease Control and Prevention [Phnom Penh]
7 WHO - World Health Organization [Phnom Penh]
8 The Peter Doherty Institute for Infection and Immunity [Melbourne]
9 Monash University [Melbourne]
10 GlaxoSmithKline Vaccines [Singapore]

Background: Influenza virus circulation is monitored through the Cambodian in- fluenza-like illness (ILI) sentinel surveillance system and isolates are characterized by the National Influenza Centre (NIC). Seasonal influenza circulation has previ- ously been characterized by year-round activity and a peak during the rainy season (June-November). Objectives: We documented the circulation of seasonal influenza in Cambodia for 2012-2015 and investigated genetic, antigenic, and antiviral resistance characteris- tics of influenza isolates. Patients/Methods: Respiratory samples were collected from patients presenting with influenza-like illness (ILI) at 11 hospitals throughout Cambodia. First-line screen- ing was conducted by the National Institute of Public Health and the Armed Forces Research Institute of Medical Sciences. Confirmation of testing and genetic, anti- genic and antiviral resistance characterization was conducted by Institute Pasteur in Cambodia, the NIC. Additional virus characterization was conducted by the WHO Collaborating Centre for Reference and Research on Influenza (Melbourne, Australia). Results: Between 2012 and 2015, 1,238 influenza-positive samples were submitted to the NIC. Influenza A(H3N2) (55.3%) was the dominant subtype, followed by in- fluenza B (30.9%; predominantly B/Yamagata-lineage) and A(H1N1)pdm09 (13.9%). Circulation of influenza viruses began earlier in 2014 and 2015 than previously de- scribed, coincident with the emergence of A(H3N2) clades 3C.2a and 3C.3a, respec- tively. There was high diversity in the antigenicity of A(H3N2) viruses, and to a smaller extent influenza B viruses, during this period, with some mismatches with the north- ern and southern hemisphere vaccine formulations. All isolates tested were suscepti- ble to the influenza antiviral drugs oseltamivir and zanamivir. Conclusions: Seasonal and year-round co-circulation of multiple influenza types/sub- types were detected in Cambodia during 2012-2015.

Keywords: A(H1N1)pdm09; A(H3N2); Cambodia; influenza A virus; influenza B virus; surveillance

Domains: Life Sciences [q-bio]; Microbiology and Parasitology; Virology; Life Sciences [q-bio]; Biodiversity; Systematics, Phylogenetics and taxonomy

Paul F. Horwood, Erik A. Karlsson, Srey Viseth Horm, Sovann Ly, Seng Heng, et al.. Circulation and characterization of seasonal influenza viruses in Cambodia, 2012‐2015. Influenza and Other Respiratory Viruses, 2019, 13 (5), pp.465 - 476. ⟨10.1111/irv.12647⟩. ⟨pasteur-03214750⟩