Jpn. J. Infect. Dis., 65 (4), 295-300, 2012

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Yoshikazu Iha^1,4, Futoshi Higa¹*, Satoko Sunagawa^1,2, Masamitsu Naka³, Haley L. Cash¹, Kazuya Miyagi¹, Shusaku Haranaga¹, Masao Tateyama¹, Tsukasa Uno², and Jiro Fujita¹

¹Department of Infectious, Respiratory, and Digestive Medicine, Control and Prevention of Infectious Diseases, ²Department of Hospital Pharmacy, and ⁴Department of Hospital Nursing, Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215; and ³Clinical Laboratory Center, the Medical Association of Naha City, Okinawa 900-0034, Japan

(Received October 25, 2011. Accepted April 17, 2012)

*Corresponding author: Mailing address: Department of Infectious, Respiratory, and Digestive Medicine, Control and Prevention of Infectious Diseases, Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan. Tel: +81-98-895-1144, Fax: +81-98-895-1414, E-mail: このメールアドレスはスパムボットから保護されています。閲覧するにはJavaScriptを有効にする必要があります。

SUMMARY: Climatic conditions may have affected the incidence of influenza during the pandemic of 2009 as well as at other times. This study evaluated the effects of climatic conditions on influenza incidence in Okinawa, a subtropical region in Japan, during the 2009 pandemic using surveillance data from rapid antigen test (RAT) results. Weekly RAT results performed in four acute care hospitals in the Naha region of the Okinawa Islands from January 2007 to July 2011 were anonymously collected for surveillance of regional influenza prevalence. Intense epidemic peaks were noted in August 2009 and December 2009–January 2010 during the influenza pandemic of 2009. RAT positivity rates were lower during the pandemic period than during the pre- and post-pandemic periods. Lower ambient temperature was associated with higher influenza incidence during pre- and post-pandemic periods but not during the pandemic of 2009. Lower relative humidity was associated with higher influenza incidence during the pandemic as well as during the other two periods. The association of climatic conditions and influenza incidence was less prominent during the pandemic of 2009 than during pre- and post-pandemic periods.