The number of influenza patients nationwide has surged in the past week to about 640,000, compared to about 330,000 patients recorded the previous week, the National Institute of Infectious Diseases said Friday.

NIID officials believe almost all of these people are suffering from the new strain of influenza.

The number of flu patients reported by about 5,000 designated medical institutions across the country from Oct. 5 to Sunday was 12.92 per facility--double the 6.4 patients recorded during the Sept. 28 to Oct. 4 period, NIID officials said.

This is the first time since the new-flu epidemic started that the number of patients per facility has exceeded the national warning level of 10 patients per facility.

By prefecture, Hokkaido had the highest ratio, at 38.96 patients per facility--easily exceeding the prefectural alarm level of 30--followed by Aichi Prefecture with 23.52, Fukuoka Prefecture with 23.48, Kanagawa Prefecture with 21.63, Okinawa Prefecture with 19.48, Tokyo with 18.98 and Osaka Prefecture with 16.96.

At a press conference Friday, Shinya Adachi, parliamentary secretary for health, labor and welfare, said, "Emergency units for outpatients are overcrowded due to a sudden surge in the number of [new-flu] patients."

In addition, people are streaming into medical facilities seeking examinations to verify potential cases of new flu, motivated by such circumstances as family members displaying symptoms of the new flu.

1 dose deemed effective

Inoculation with domestically produced new-flu vaccines is effective for a healthy adult even if only a single dose of vaccine is used, the National Hospital Organization said Friday.

The organization reported the results of clinical tests to a specialists' meeting held at the Health, Labor and Welfare Ministry.

Those attending the meeting will discuss a review of the current inoculation plan under which the organization assumed that the vaccine needed to be administered twice.

The clinical tests have been held by the organization since Sept. 17 on a group of 200 healthy adults aged 20 years or older, the organization said.

When the organization inspected the blood before and after the vaccine was administered once to the test subjects, it confirmed the effectiveness of the vaccine. New-flu antibodies increased in the blood of 72 out of 96, or 75 percent, of subjects who were administered a normal dose of the vaccine, according to the tests.