Tokyo - Japan will set up fever clinics across the nation to treat patients with swine flu if the disease reaches Japan, a ministry official said Thursday.

The government's plan to designate some medical facilities as fever clinics was intended to prevent in-hospital spread of flu infections, according to the Health, Welfare and Labour Ministry.

A government task force decided on the new scheme after the World Health Organization upgraded its influenza alert level to phase 5, which means the world is facing an imminent risk of a pandemic from swine flu. Phase 6 is the highest state of alert.

Japan would not "fundamentally change its present policy immediately because of the upgrading of the alert phase, but will thoroughly carry out preventive measures to keep the flu at bay," Chief Cabinet Secretary Takeo Kawamura said.

Kawamura was referring to the government's policy of advising citizens to act carefully when travelling abroad but did not intend to urge them to postpone traveling to countries affected by the flu, other than Mexico.

There have been no confirmed or suspected cases of swine flu infections so far in Japan.

The flu death toll rose to 159, and the number of infections is 2,498 in Mexico's flu outbreak. Of these, 1,311 people remain in hospital and most have not yet been identified as swine flu cases. Mexico confirmed 91 swine-flu infections and eight deaths.