Laboratory and Epidemiology Communications Low Hemagglutinin-Titer Strains of Pandemic Influenza A (H1N1) 2009 Virus Circulated in Toyama Prefecture, Japan, during the 2009-2011 Influenza Seasons

*Corresponding author: Mailing address: Department of Virology, Toyama Institute of Health, 17-1 Nakataikoyama, Imizu-shi, Toyama 939-0363, Japan. Tel:+81-76656-8143, Fax: +81-766-56-7326, E-mail: masatsugu. obuchi@pref.toyama.lg.jp Fig. 1. Comparison of the HA titers of pandemic influenza A (H1N1) 2009 virus isolates obtained during the 2009–2010 and 2010–2011 seasons in Toyama Prefecture, Japan. HA assay was performed with 0.75z guinea pig erythrocytes. Jpn. J. Infect. Dis., 64, 2011