That compares with 416 the previous week and is the highest number of new test-confirmed cases reported in a week since the country began tracking the weekly reports in 1993, TT news agency reported.
State epidemiologist Annika Linde told TT last week an estimated 100,000 Swedes were sick with flu the week of Feb. 12 -- many more than the confirmed number of cases.
Anders Wallenstein, a specialist at the Swedish Institute for Communicable Disease Control, said that total number likely had increased last week.
The flu has hit hardest in the Umea area in northern Sweden, on the west coast and in Skane in the south, officials said.
Experts predict the number of people coming down with the flu will rise for a few more weeks, but maybe not as quickly.