The current seasonal vaccine against the flu would have little effect in fighting swine flu, the World Health Organization said Friday, as it confirmed more human cases around the world.

Beth Weiman, a lead microbiologist, tests a suspected swine flu sample at the Washington State Public Health Laboratories in Shoreline, Wash. (Elaine Thompson/Associated Press)

Though testing is still being done, the consensus among medical experts is that there is very little chance the seasonal vaccine will be effective against the current outbreak of the H1N1 virus, Marie-Paule Kieny, director of WHO's initiative for vaccine research, told a news conference in Geneva on Friday.

"It would be critically important to have a vaccine if you want to stop a pandemic which might be coming with this virus," Kieny said.

But WHO has "no doubt making a successful vaccine is possible" in a relatively short period of time because there is already a great deal of experience developing vaccines to combat against seasonal influenza, Kieny said.

It will be at least four months before the first doses of a new vaccine would be available to immunize against the H1N1 virus, she said.

Samples that are needed to create a vaccine will be sent to manufacturers by the end of May, Kieny said.

WHO does not yet have any estimates on the cost of developing or administering a vaccine.

The organization has been speaking with Swiss drug maker Roche Holding AG, which makes Tamiflu, an antiviral that has proven effective against the virus, about making it available to developing countries deemed in need of supplies, said WHO spokesman Thomas Abraham.

The manufacturing of the vaccine will proceed unless there is a clear indication that there is no longer a need for it, Kieny said.

Police officers wearing masks seal off Metro Park Hotel in Hong Kong on Friday as the first swine flu case in the city was confirmed. (Vincent Yu/Associated Press)

Hundreds of tourists and employees were under quarantine in a downtown Hong Kong hotel Saturday after a Mexican guest tested positive for swine flu. With the outbreak on its doorstep, China suspended direct flights from Mexico.

Officials were trying to notify the other 140 people who were on the same flight as the guest, who flew from Mexico to Hong Kong via Shanghai on China Eastern Airlines flight MU505 on Thursday afternoon.

Hours after the first confirmed case in Asia was reported, the continent got its second: tests showed a South Korean woman also had the disease. She has been under quarantine since returning earlier this week from Mexico.

WHO is reporting 365 confirmed cases in 13 countries:

• 141 in the United States (one death).
• 156 in Mexico (nine deaths).
• 34 confirmed cases in Canada.
• 13 in Spain.
• Eight in the United Kingdom.
• Three in Germany.
• Three in New Zealand.
• Two in Israel.
• One in Austria.
• One in the Netherlands.
• One in Switzerland.
• One in Hong Kong.
• One in Denmark.

The number of confirmed cases and deaths reported by WHO may not match the numbers reported by countries, because they may not yet have reported them to the international health body.

For example, Canadian officials have confirmed 55 cases, but they are not yet included in WHO's official tally, nor is South Korea's first case confirmed on Friday.

Case found in N.B.

On Friday, New Brunswick health officials confirmed the province's first case of swine flu — in a woman in her 20s who had recently returned from Mexico.

Health officials in Denmark also reported on Friday that it had confirmed its first case of the virus.

The U.S. Centers for Disease Control and Prevention said on Friday the country's number of confirmed cases had risen to 141 of the H1N1 flu in 19 states.

WHO raised its global pandemic alert level to five, its second-highest level, on Wednesday. Phase 5 is called when there is human-to-human spread of a virus in at least two countries in one region, according to the organization's pandemic response guidelines.

The classification means a pandemic is imminent and countries must finalize preparations to deal with the outbreak of swine flu, officials said.

WHO's emergency committee, which can recommend a change to the pandemic alert level, is not scheduled to hold any meetings on Friday, though the committee will convene if the flu outbreaks widens, officials said.

To declare a full-blown pandemic, WHO would have to be convinced the new virus is spreading in a sustained way among communities in another region besides North America.

Watching for human-to-human spread

Two women chat in the trendy la Condesa neighbourhood of Mexico City. Streets and parks in the area are all but empty as the Mexican government warns people to stay inside to prevent the further spread of swine flu. (Submitted by Kristan Taylor)

Abraham said officials are watching a case in Spain where the patient had not travelled to Mexico. That would indicate human-to-human spread.

"We need to be sure it is actually established in communities," Abraham said, "not just stray cases of a traveller passing it on to one person or two people."

British health officials also reported Friday that a swine flu case has been found in a Scottish man who had not been to Mexico.

Over the next week, medical experts will be able to get a better understanding of how transmissible the virus is, said Dr. Donald Low, medical director of Ontario's Public Health Laboratories.

The number of specimens being sent for testing in Canadian laboratories is increasing but officials are still waiting to see the number of positive results, Low said.

"This is a brand new disease," Low said. "It's a historic event. Most of us have not lived through a pandemic and we've never been in a situation where we're actually looking as it evolves."

New cases in Mexico levelling off

Mexico, which is where the outbreak is believed to have started, opted to shut down parts of the country for five days, beginning on Friday, in a bid to control the spread of the illness.

Wearing protective face masks to protect against swine flu contagion, Alan Martinez, left, and Jaqueline Garcia Gonzalez look at each other while waiting in line to be examined by a doctor at a mobile medical brigade set up in downtown Mexico City. (Rodrigo Abd/Associated Press)

New cases and suspected deaths in Mexico appear to be leveling off, said Mexican Health Secretary Jose Angel Cordova.

Cordova said the public hospitals that treat roughly half the country admitted just 46 patients with severe flu symptoms on Thursday, down from 212 patients on April 20. "This is encouraging," he said.

Mexico raised its confirmed swine flu death toll on Friday from 15 to 16 and said the total number of confirmed cases of the virus had risen to 397.

Shutting down non-essential government services and private businesses should help further slow the spread of the virus, according to officials.

Mexican President Felipe Calderon said authorities would use the extensive shutdown to consider whether to extend emergency measures or ease some restrictions. The five days include Friday's Labour Day holiday, the weekend, and the Cinco de Mayo observance on Monday, minimizing the disruption.

With files from The Associated Press