BEIJING, Jan. 9 (Xinhua) -- Schools in China are ordered to improve sanitary conditions and upgrade diseases prevention efforts, as contagious diseases have reportedly affected about 490 students in recent three months.

    The Ministry of Education issued an health alert circular on Tuesday, asking schools to take better prevention measures that can effectively deter the spread of contagious diseases among students.

    The ministry said local education authorities and school heads are to blame for the health hazard incidents caused by the lack of prevention measures.

    The incidents included Hepatitis-A infection cases in Hunan, Guizhou, Jiangxi, Chongqing and Guangxi, which involved more than 350 students.

    The ministry has ordered a disease prevention overhaul nationwide.