Canadian officials reacted with outrage to a World Health Organization warning that travelers should avoid Toronto because of the severe acute respiratory syndrome outbreak.

As Toronto businesses braced for disaster, Canada's SARS (more news | Web) outbreak claimed its 16th victim Wednesday: a 78-year old woman who officials said had a pre-existing medical condition.

"I've never been angrier in my life," Mayor Mel Lastman said. "I'm shocked. The medical evidence before us does not support this advisory."

The powerful influence of the travel advisory, issued by the Geneva-based organization, became immediately apparent as Britain followed suit, warning its citizens to avoid travel to Canada's largest city.

The Canadian province of Nova Scotia briefly did the same, but did a rapid about-face after a previously planned conference call of federal and provincial health ministers.

The city joins the WHO's list of SARS hot zones -- Hong Kong, Beijing, and the Chinese provinces of Guangdong and Shanxi.

But Canadian experts noted that of the 267 probable and suspect cases Ontario has recorded since the start of the outbreak, only 124 remain in hospital or under active surveillance in their homes.

"It is perfectly safe to walk down the street in Toronto. And all of us walk down the street every day, without masks," said Dr. James Young, Ontario's commissioner of public security.

The Health Canada agency plans to challenge the decision in the hopes of getting the WHO to reverse it, said Dr. Paul Gully, the department's senior director general for population and public health. On Wednesday, the organization said any SARS travel advisory it issues must remain in place for three weeks -- two full incubation periods for the disease.

The U.S. Centers for Disease Control and Prevention has issued a travel alert to Americans traveling to Toronto, suggesting they avoid health-care facilities and monitor their health for 10 days following their return. But it has not urged Americans not to come to Toronto. It has issued such warnings for Hong Kong and China.

Dr. David Heymann of the World Health Organization said the new travel alert, which includes Shanxi, was necessary because "these areas now have quite a high magnitude of disease, a great risk of transmission locally ... and also they've been exporting cases to other countries."

News of the WHO warning was met with dread by Toronto's business community, already reeling from the financial repercussions of the SARS outbreak so far in the city.

David Dodge, governor of the Bank of Canada, predicted the drop in travelers will affect the entire country. He said Toronto accounts for about a fifth of the total economic activity in the country.

Major League Baseball officials advised caution when players visit Toronto. Officials initially told them to avoid signing autographs, but later amended that.

The teams will be told to avoid crowds, hospitals and public transportation. And if they want to sign autographs, they ought to use their own pens, said Dr. Elliot Pellman, the league's medical adviser.