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Review
. 2016;55(24):3579-3584.
doi: 10.2169/internalmedicine.55.7107. Epub 2016 Dec 15.

An Epidemiological Analysis of Summer Influenza Epidemics in Okinawa

Satoko Sunagawa  1 , Yoshikazu Iha, Katsuya Taira, Sho Okano, Takeshi Kinjo, Futoshi Higa, Kazufumi Kuba, Masao Tateyama, Katsunori Nakamura, Shota Nakamura, Daisuke Motooka, Toshihiro Horii, Gretchen L Parrott, Jiro Fujita
Affiliations
Review

An Epidemiological Analysis of Summer Influenza Epidemics in Okinawa

Satoko Sunagawa et al. Intern Med. 2016.

Abstract

Objective This study evaluates the difference between winter influenza and summer influenza in Okinawa. Methods From January 2007 to June 2014, weekly rapid antigen test (RAT) results performed in four acute care hospitals were collected for the surveillance of regional influenza prevalence in the Naha region of the Okinawa Islands. Results An antigenic data analysis revealed that multiple H1N1 and H3N2 viruses consistently co-circulate in Okinawa, creating synchronized seasonal patterns and a high genetic diversity of influenza A. Additionally, influenza B viruses play a significant role in summer epidemics, almost every year. To further understand influenza epidemics during the summer in Okinawa, we evaluated the full genome sequences of some representative human influenza A and influenza B viruses isolated in Okinawa. Phylogenetic data analysis also revealed that multiple H1N1 and H3N2 viruses consistently co-circulate in Okinawa. Conclusion This surveillance revealed a distinct epidemic pattern of seasonal and pandemic influenza in this subtropical region.

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Figures

Figure 1.
Figure 1.
Incidence of influenza A and B from 2007 to 2014 in four participating hospitals in the Naha region of Okinawa, Japan. Green designates the number of rapid antigen tests performed, blue designates the number of positive results for influenza A virus, and red designates the number of positive results for influenza B.
Figure 2.
Figure 2.
A genomic analysis of the hemagglutinin gene of A/H3N2 viruses obtained in Okinawa.
See this image and copyright information in PMC

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