感染症と治療ジャーナル

抽象的な

Characterization of Influenza Viruses Responsible for Acute Respiratory Illness in Cambodia from 2015 to 2016

Bonath Ka, Martine Valette, Monidarin Chou and Bruno Lina

Background: Acute Respiratory Infection (ARI) is a leading cause of morbidity and mortality worldwide. During a study describing the circulation and the prevalence of respiratory viruses and bacteria in Cambodia, an ancillary analysis focussed on influenza viruses.

Method: Between July 2015 and December 2016, 18 to 50-year-old patients presenting with ARI (cough+sore throat+fever ≥ 37.5°C) and attending four referral hospitals were included. In each site, out-patients, in-patients and non-ARI controls (outpatients with non-infectious diseases) were recruited. Clinical information and nasal washes were collected. Influenza and other respiratory pathogens were screened by multiplex real-time PCR. Each influenza virus detected was subsequently typed, subtyped, cultured, tested for Neuraminidase Inhibitors susceptibility and sequenced by direct whole genome sequencing.

Results: Amongst the 1006 included patients, 48 were positive for influenza (5.4%), including 36 Influenza A (19 A(H1N1)pdm09 and 17 A(H3N2)), 11 Influenza B (9 Yamagata and 2 Victoria) and one A(H1N1)pdm09+B Victoria co-infection. Overall, 11 in-patients (6 H1N1pdm09, 2 H3N2, 2 B and 1 H1N1pdm09+B co-infection), 36 out-patients (12 A(H1N1)pdm09, 15 A(H3N2) and 9 B) and 1 control (1 H1N1pdm09) were positive. These viruses circulated year-round with 2 peaks during the rainy season (August 2015 and June 2016), and a switch from A(H3N2) to BYamagata
and to A(H1N1)pdm09 with almost no overlap was observed. All viruses were similar to the vaccine strains, and susceptible to NAI.

Conclusion: We report a low prevalence of influenza in this adult population (5.4%). Most cases were due to
influenza A (77.1%) with a balanced distribution between A(H1N1)pdm09 and A(H3N2) (20 vs. 17), and a higher
proportion of A(H1N1)pdm09 in in-patients. No molecular difference was observed between viruses of in- and outpatients,
and no resistance was detected. The year-round circulation and virus switch is similar to this reported in
other sub-tropical areas.