The World Health Organization (search) said Tuesday it has decided against reinstating a travel warning to Canada's largest city despite a sickened U.S. traveler and a new suspected hospital outbreak in the Toronto (search) area.

A U.S. man who visited Toronto last month came down with SARS (search) after returning to his home near Raleigh, N.C., U.S. health officials confirmed.

The man visited a Toronto hospital patient who was sharing a room with people who later came down with SARS, officials said. His diagnosis raised the possibility of SARS spreading from people carrying the virus but not showing any symptoms.

Until now, health authorities have worked under the assumption that only symptomatic patients spread the illness.

Toronto has been linked to 11 — or 16 percent — of the U.S. probable cases, said Llelwyn Grant, a spokesman for the U.S. Centers for Disease Control and Prevention.

The Canadian city has had the highest concentration of SARS cases outside of Asia, with 33 deaths reported so far. Officials reported 64 probable cases Tuesday, down two from the previous day.

So far, Canada has reported 33 deaths and 216 cases, making it the world's No. 4 trouble spot.

Taiwan was angry Wednesday about a WHO decision not to lift a SARS travel advisory for the island as it has done for Canada.

Meanwhile, a top WHO disease expert sought answers from Beijing about a sharp drop in reported SARS cases there that hasn't matched more gradual decreases elsewhere. He declined to say whether WHO was considering lifting a travel advisory for the Chinese capital.

WHO considers the export of SARS cases a key factor in deciding to impose travel advisories, which governments are eager to avoid because of the cloud it casts over their tourism industries.

On the other hand, Taiwanese officials said Wednesday that WHO rejected the island's request to have its advisory canceled because the agency feared Taiwan might be exporting SARS cases.

Severe acute respiratory syndrome has infected more than 8,300 worldwide and has killed at least 790 — most of them in Asia.

The U.N. health agency has requested more information about six cases involving people who developed SARS symptoms after leaving Taiwan, said Su Yi-jen, chief of Taiwan's Center for Disease Control.

The Taiwanese official said the WHO decision was unfair and that Taiwan has filed a protest with the Geneva-based organization.

"None of the countries where those six people traveled to is treating them as SARS cases," Su said.

WHO is especially concerned about a Taiwanese traveler who developed SARS symptoms in Sao Paulo, Brazil, on June 4, Su said. The other sick travelers — who left Taiwan between March 4 and May 22 — went to the United States, South Korea, the Philippines, Germany and Thailand, he said.

The world's No. 3 SARS hotspot, Taiwan has reported 81 deaths and 687 cases. But in recent days, the number of new cases has plunged and a death hasn't been reported in 14 days.

Steven Kuo, spokesman for Taiwan's SARS Control Committee, said some Taiwanese officials suspect WHO is using a double standard or possibly caving in to political pressure when deciding when to cancel travel warnings.

"We have some feeling that there's something going on behind the scenes, but to be honest, I'm not too familiar with the Toronto case," Kuo said.

WHO also has a travel advisory against China's capital, Beijing. But a senior WHO official, Dr. David Heymann, wouldn't say on Wednesday whether the agency planned to drop the warning soon.

Heymann, the agency's Geneva-based chief of communicable diseases, did say that China needed to clarify data showing a sharp drop in new SARS cases. The disease has dropped more gradually in other affected areas.

"We have no reason to doubt this information," Heymann told reporters. "We have a few questions that we'd like to ask, to clarify a few things."

Heymann didn't give any details of what WHO wanted to clarify.

SARS has killed 343 people in China and has sickened more than 5,000.