The US was one of the last countries in the world to catch the 'Love Bug' computer virus that had swept through Asia and Europe while most Americans were still asleep.

Peter Tibbett, chief technologist at security company ICSA.net, estimated that the US had lost $100m by 9am Thursday in software damage and lost commerce, and said that a further $1bn would be lost by Monday morning.

The so-called Love Bug was first reported in Asia and swept through Europe early on Thursday. It is sent as an attachment to emails entitled 'ILOVEYOU' and is understood to have originated from the Philippines. The code in the software mentions 'Manila, Philippines,' and infected computers have been directed to four websites in that country.

The bug found its way into the email systems of America Online (AOL), the US's largest ISP. Although the company chose not to close down its servers, it did send out an email alert and told users to check its antivirus centre and messageboards.

The virus also affected servers at US media conglomerate Time Warner. A spokesman in New York said: "It's all over our system."

In California, telco Pacific Bell shut down its email servers to stop the bug from spreading.

A White House spokesman said that so far the virus has not penetrated the administration's systems, "but there have been some reports around the government about it", he said.