日本流感疫情持续高位，七成地区达“警报”级别

Group 1 - The core point of the article highlights a significant increase in flu cases in Japan, with nearly 160,000 reported cases in a week, leading to 35 out of 47 prefectures reaching "alert" levels for flu outbreaks [1] - As of February 15, over 8,174 schools and kindergartens across Japan have either fully or partially suspended classes due to the flu outbreak [1] - The flu season in Japan is expected to last until March or April, with the possibility of patients experiencing infections twice during this period [2] Group 2 - The recent flu season in Japan has shown an unusual pattern with two waves of high incidence, the first wave primarily involving H1N1 (A strain) and the second wave dominated by H3N2 (B strain) [2] - The increase in flu cases is attributed to dry weather conditions, which have weakened patients' immune systems and facilitated virus proliferation [1]