BEIJING, June 12 (Xinhua) -- China is strengthening prevention and control of bird flu although no new human cases have been confirmed for more than a month, a health official said Monday.

    "We are still keeping a close eye on bird flu and have strengthened scientific research and nationwide surveillance," said Ministry of Health spokesman Mao Qun'an.

    So far, the virus outside of the human infections had shown no sign of mutation, and human-to-human transmission was still unproved in clinical studies, he said.

    China had enhanced research in human vaccines and drugs as well, he added.

    Monitoring of unexplained pneumonia cases had also been strengthened by the ministry, which required local health institutes to screen pneumonia cases and report immediately to health authorities cases with unknown causes, Mao said.

    Meanwhile, the Chinese government was working closely with international organizations in fighting bird flu.

    Last week, China joined in a pandemic response exercise in prevention and control of bird flu held by the Asia Pacific Economic Cooperation (APEC), which aimed to test the preparations of the organization's members for an epidemic in terms of information sharing, technological support and prevention of cross-border spread.

    Mao reiterated that the public should stay away from sick or dead poultry.

    China has reported 18 cases of human infection of bird flu since last November with 12 fatalities. The last case was confirmed on April 27.

    Globally, 225 human infections, including 128 deaths, have been recorded by the World Health Organization (WHO), according to the WHO website.

    At the 59th World Health Assembly held in late May, members agreed on a resolution to voluntarily implement the WHO's International Health Regulations a year earlier than scheduled in the field of flu pandemic prevention.

    In the resolution, WHO members agreed to give transparent and urgent notice of any probable or confirmed human cases of bird flu, and pledged to provide financial and other assistance to governments that lack the means to respond to an avian or pandemic-type flu outbreak. Enditem