A new computer virus, the "Fizzer" worm, spread rapidly across the Internet on Monday, infecting computer users in Asia, Europe and the United States, anti-virus officials said.Businesses in Asia were the first to report the attack. By mid-day in Europe, tens of thousands of computer users had been hit, with more cases expected in North America as the business day wears on. UK-based virus detection firm MessageLabs recorded 17,765 cases in 24 hours. "We've upgraded it to high-risk just for the fact that we've seen so many in the last day," said Mark Toshack,a virus analyst at MessageLabs.