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J Clin Microbiol. 2009 Jan 21. [Epub ahead of print]
Epidemiologic study of influenza infection in Okinawa, Japan, from 2001 to 2007: changing patterns of seasonality and amantadine-resistant influenza A.
Suzuki Y, Taira K, Saito R, Nidaira M, Okano S, Zaraket H, Suzuki H. - Department of Public Health, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan; Department of Biological Science, Okinawa Prefectural Institute of Health and Environment, Okinawa, Japan.
To clarify influenza seasonal patterns and the prevalence of amantadine-resistant influenza A viruses in Okinawa located in southern extremity of Japan with subtropical climate, we conducted a laboratory-based study of influenza virus infections from 2001 to 2007.
The annual outbreaks tended to show two peaks in Okinawa in summer and winter, although main islands of Japan, located in temperate climate area, showed only winter activity of influenza.
Epidemic types and subtypes in Okinawa mostly matched with those of main islands of Japan in winter, so did with Taiwan in summer.
Rates of amantadine resistance dramatically increased from 7.3% in the 2002-2003 season to 90.0% in 2005 summer, and such a high rate of resistant continued for the rest of the study.
Phylogenetic analysis of the hemagglutinin (HA) gene of A/H3N2 isolates during 2002-2007 formed a monophyletic lineage that was divided into four period groups.
Each group included amantadine sensitive and resistant viruses within independent clusters.
In the 2005-2006 season, all of the amantadine-resistant viruses were clustered in clade N with dual (193 and 225 positions) amino acid mutations in their HA1 subunit.
Clade N amantadine-resistant viruses in 2005 existed in Okinawa several months before its circulation in main islands of Japan.
In conclusion, surveillance in Okinawa is important to monitor the influenza circulation to elucidate the dynamics of virus transmission in a border area between temperate and subtropical areas as one of the best sentinel points in Japan.
PMID: 19158265 [PubMed - as supplied by publisher
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Epidemiologic study of influenza infection in Okinawa, Japan, from 2001 to 2007: changing patterns of seasonality and amantadine-resistant influenza A.
Suzuki Y, Taira K, Saito R, Nidaira M, Okano S, Zaraket H, Suzuki H. - Department of Public Health, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan; Department of Biological Science, Okinawa Prefectural Institute of Health and Environment, Okinawa, Japan.
To clarify influenza seasonal patterns and the prevalence of amantadine-resistant influenza A viruses in Okinawa located in southern extremity of Japan with subtropical climate, we conducted a laboratory-based study of influenza virus infections from 2001 to 2007.
The annual outbreaks tended to show two peaks in Okinawa in summer and winter, although main islands of Japan, located in temperate climate area, showed only winter activity of influenza.
Epidemic types and subtypes in Okinawa mostly matched with those of main islands of Japan in winter, so did with Taiwan in summer.
Rates of amantadine resistance dramatically increased from 7.3% in the 2002-2003 season to 90.0% in 2005 summer, and such a high rate of resistant continued for the rest of the study.
Phylogenetic analysis of the hemagglutinin (HA) gene of A/H3N2 isolates during 2002-2007 formed a monophyletic lineage that was divided into four period groups.
Each group included amantadine sensitive and resistant viruses within independent clusters.
In the 2005-2006 season, all of the amantadine-resistant viruses were clustered in clade N with dual (193 and 225 positions) amino acid mutations in their HA1 subunit.
Clade N amantadine-resistant viruses in 2005 existed in Okinawa several months before its circulation in main islands of Japan.
In conclusion, surveillance in Okinawa is important to monitor the influenza circulation to elucidate the dynamics of virus transmission in a border area between temperate and subtropical areas as one of the best sentinel points in Japan.
PMID: 19158265 [PubMed - as supplied by publisher
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