The health ministry has decided to designate the deadly H5N1 strain of avian influenza as an infectious disease, officials said.

The designation will enable authorities to force infected persons to be hospitalized for treatment and impose restrictions on their work activities, the officials of the Health, Labor and Welfare Ministry said.

The plan was approved at a meeting Friday of the ministry's Health Sciences Council and will be implemented this summer, the officials said.

The last time the ministry took such a step was in July 2003, when severe acute respiratory syndrome, or SARS, was designated as an infectious disease.

The government had initially planned to designate the H5N1 strain of bird flu as an infectious disease once an outbreak was confirmed.

But it decided to proceed with the designation anyway in part because H5N1 has been spreading rapidly in various parts of the world, with about 190 cases of human infection confirmed since mid-2003 in nine countries in Asia and in the Middle East, the officials said.

The health ministry also considers it necessary to take preventive measures because H5N1 has the potential to mutate into a form that can be passed easily from person to person and because the World Health Organization has called for isolating a patient infected with H5N1. Currently, the H5N1 strain of bird flu falls in a category of diseases for which authorities are not allowed to isolate a patient.