MANILA, June 12 (Xinhua) -- The chief of the World Health Organization (WHO) in Western Pacific region Friday urged underdeveloped countries to keep vigilant of the health threat brought by waves of pandemics, after the Geneva-based U.N. body declared the highest alert for the spread of the A/H1N1 influenza virus.

    "The world and in particular the Western Pacific Region needs to be on its toes," said Dr Shin Young-soo, WHO's Regional Director for the Western Pacific, warning of "more severe disease" riding on the next waves of the flu pandemic to attack less developed countries which may have poor health care systems and many people with underlying health problems.

    As of June 12, more than 30,000 laboratory-confirmed cases of influenza A/H1N1 had been reported worldwide, while in the Western Pacific Region more than 2,200 cases had been reported in nine countries. However, according to the WHO, there have been no deaths from influenza A/H1N1 in the Western Pacific.

    The WHO, on June 11, raised its influenza pandemic alert level for the virus to Phase six, which signifies the beginning of global spread as community-based spread has appeared in two regions -- the North America where the virus originated and the Oceania.

    Dr Shin Young-soo, however, said that by now the influenza A/H1N1 is still a virus of moderate severity which produces mild illness in the majority of cases.

    "Phase six indicates how far the pandemic has spread, and is not a sign the disease has grown more dangerous," he said.

    WHO advises governments to calibrate their responses to match the circumstances in their communities. This may mean that some countries will focus in the short term on containment measures, while others will move from containment to mitigation and care of the vulnerable members of society.

    Calibration of responses should be in keeping with the outbreak situation in each country. Countries with no cases are advised to remain vigilant and enhance surveillance, Dr Shin said. Countries with widespread community transmission should ensure patients receive prompt health care, and consider shifting from containment to mitigation while taking steps to increase surveillance efforts and laboratory capacity.

Special Report:  World Tackles A/H1N1 Flu