The World Health Organization raised its pandemic alert level to Phase 4 on Monday, verifying human-to-human transmission of swine flu, as the suspected death toll from the virus in Mexico hit 149.

Meanwhile, the United States cautioned against non-essential travel to Mexico and tightened its borders along the southern states. The European Union also advised Europeans to be wary about travelling on Mexico -- and parts of the U.S.

In newly-revised alert levels released this week, WHO defines Phase 4 as "human-to-human transmission of an animal or human-animal influenza reassortant virus able to sustain community-level outbreaks has been verified."

Phase 4 normally calls on affected countries to contain the outbreak. But WHO spokesperson Dr. Keiji Fukuda said that "given the current situation," the the focus should be on mitigation.

"This virus has already spread quite far, so at this time containment is not a feasible option," he said.

Fukuda also said the WHO director-general has recommended not closing borders or restricting travel. However, those who are sick should delay their travel plans.

Phase 5 would mean there is a high-to-certain probability of a pandemic, while Phase 6 means a pandemic is in progress.

The swine flu outbreak has now reached beyond North America, reaching into Europe. So far, confirmed cases have been found in:

  • United States: 42
  • Mexico: 26
  • Canada: 6
  • Spain: 1
  • Scotland: 2

Mexico has suffered the brunt of the outbreak. Schools across the country were ordered to close Monday as officials revealed that the suspected death toll from swine flu has reached 149.

Health Secretary Jose Angel Cordova said only 20 people have been confirmed to have died directly from swine flu.

Cordova said tests were still being conducted on the rest of the dead.

In total, Cordova said 1,995 people have been hospitalized in Mexico with serious cases of pneumonia since the first case of swine flu was reported on April 13.

Of those hospitalized, 1,070 have since been released.

All schools have been suspended until May 6.

In Mexico City, CTV's Tom Walters said there is a sense of fear among residents.

"We were very struck yesterday by just how many people you see wearing masks and by how many people are avoiding public gatherings," Walters reported Monday morning.

"...There is a great effort being made here to keep people from interacting and certainly to keep them from gathering in groups."

Swine flu, also known as A H1N1, is normally contracted through contact with pigs.

However, it appears that this strain is spread through human-to-human contact.

Symptoms include fever, muscle and joint pain, cough, sore throat, eye pain, shortness of breath and extreme fatigue.

Confirmed cases

Spain reported the first confirmed case of swine flu outside North America Monday.

Spain's Health Minister Trinidad Jimenez said a young man who recently returned from Mexico, where swine flu was first reported, has contracted the virus but is responding well to treatment.

Another 20 people in Spain are suspected of having the disease.

Nicola Sturgeon, Scotland's health secretary, later said two cases have been conclusively confirmed in Scotland.

In Luxembourg, European Union Health Commissioner Andorra Vassiliou told reporters that Europeans "should avoid travelling to Mexico or the United States of America unless it is very urgent for them."

In Canada, four of the six cases of swine flu are in Nova Scotia and two in British Columbia.

On Monday, U.S. President Barack Obama said the spread of swine flu was a cause for concern but "not a cause of alarm."

Obama, speaking in Washington, said his administration was "closely monitoring" cases involving swine flu and the ongoing threat.

Global spread

In New Zealand, officials reported suspected swine flu cases Monday in a second group of teenage students who had just returned from a class trip to Mexico.

Two students and a parent among the group of 15 became have mild flu symptoms.

All of the students and their families have voluntarily quarantined themselves as laboratory results are expected within days.

In Israel, two people are under observation for swine flu while France and Brazil are also reporting suspected cases.

In Asia, Singapore, Thailand, Japan, Indonesia, South Korea and the Philippines used thermal scanners to check passengers for signs of fever.

China said anyone who experiences flu-like symptoms within two weeks of arrival must report to authorities.

China and Russia have both banned imports of pork and pork products from Mexico and three U.S. states where swine flu has been reported.

Canadian infectious disease specialist Dr. Neil Rau warned Monday that the flu is going to spread quickly.

"This is going to be all over the world within the next week or two -- we know that for sure," Rau told CTV's Canada AM.

"At first that sounds scary but it may not be that dangerous a virus as we initially thought."

Rau said life must go on in Mexico and around the world.

"I think what's going to happen in Mexico is the WHO is going to finish its investigations within the next few days and the war is going to be over," Rau said.

"They're going to realize that it's not as dangerous a virus as we first thought and life will return to usual."

With files from The Associated Press