Surveillance results and analysis of influenza virus in Dongguan City from 2004 to 2006

Objective The study was conducted to determine the prevalence of influenza (flu) infection in Dongguan City. Methods Swabs of clinic suspected influenza patients were collected for the vaccination of MDCK cells with isolation culture in CO2 tank with the temperature of 33.5 ℃. Hemagglutination test-positive samples were collected for identification. Results In 2004, there were 42 influenza virus isolated cases from 412 patients, with the positive isolation rate of 10.19%, of which there were 24 cases of H3N2 and 18 cases of B-type. In 2005, there were 19 influenza virus isolated cases from 521 patients, with the positive isolation rate of 3.65%, of which there were 10 cases of H3N2, 5 cases of H1N1 and 5 cases of B-type. In 2006, there were 105 influenza virus isolated cases from 945 patients, with the positive isolation rate of 11.11%, of which there were 37 cases of H1N1 and 68 cases of B-type. Positive isolation rates between the three years had significant differences (2=24.42, P0.01), and those in 2004 and 2006 were higher than those from 2005. Conclusions The positive isolation rate in 2006 was the highest, whereas that in 2005 was the lowest. In 2004, there were only B type and H3N2 isolated, while in 2005 H1N1 added in, there was no H3N2 isolated but H1N1 and B type in 2006. The prevailing B type, followed by H1N1, was found in 2006.