The World Health Organization has raised its alert level to Phase 5, meaning the probability of a pandemic is "high to certain," as swine flu spreads around the planet.
"Influenza pandemics must be taken seriously precisely because of their capacity to spread rapidly through every country in the world," Margaret Chan, WHO director-general, told reporters Wednesday.
"On the positive side, the world is better prepared for an influenza pandemic than at any time in history."
She said increased investment in preparation measures for the avian flu virus has resulted in quick action on the new threat of swine flu.
Phase 5 is the second-highest pandemic alert level. Phase 6 means a pandemic is in progress, and there are sustained outbreaks in more than one region of the world.
Dr. Keiji Fukuda, a spokesperson for the agency, said the virus has quickly spread throughout the world due to a combination of international travel and person-to-person transmission.
"It's clear that the virus is spreading and we don't see any evidence of this slowing down at this point," Fukuda said at an earlier news conference in Geneva, Switzerland.
While the virus has been largely mild in nature outside of Mexico -- where it is the suspected cause of more than 150 deaths -- scientists are not clear how the swine flu will develop in future.
"We don't quite know how this is going to evolve, but we will monitor the situation very carefully, we will report the findings as they come available to us," Fukuda said.
The latest update from the WHO came on the same day that U.S. officials confirmed the first swine flu death outside of Mexico.
A 23-month-old Mexican boy died at a Houston hospital on Monday evening. Tests have since confirmed that swine flu was the cause.
Houston health official David Persse said the little boy first fell ill while visiting relatives in Brownsville, Texas, more than two weeks ago.
"This child is a resident of Mexico who travelled to Brownsville, Texas, to visit family," Persse said at a news conference Wednesday morning.
"It was there, in Brownsville, where the child first became ill and was taken to hospital."
The boy was admitted to a Brownsville hospital on April 13, and transferred to a Houston hospital the next day, he said.
Persse said the surviving family members are "asymptomatic" and not suffering from exposure to the swine flu virus at this point.
Dr. Richard Besser, acting director of the U.S. Centers for Disease Control and Prevention, confirmed the child's death from swine flu on Wednesday.
U.S. expects further swine flu deaths
Besser told CTV's Canada AM that it is likely that the U.S. will see further deaths from swine flu, as the illness spreads.
"We will expect to see more severe cases and I will expect to see more deaths," he said.
The child is believed to be the first person to die of swine flu outside of Mexico.
U.S. President Barack Obama said he wanted to convey his "thoughts and prayers" to the family of the young flu victim.
And he said U.S. citizens "should know" the government is doing everything it can to contain the swine flu threat.
Besser said authorities are still trying to determine why the majority of swine flu cases outside of Mexico have been much milder than where the virus was first identified.
Besser said authorities are now working to limit the impact of swine flu as best they can.
"When you have a new strain of infectious disease in a small, isolated area, you can talk about trying to contain," Besser said.
"When you have a disease that's already spread beyond one country's borders, or even within a country beyond a small region, you talk about what can you do to reduce the impact on people's health."
Obama said it may be necessary to close some schools if confirmed swine flu infections are identified.
He said public health officials have recommended "that schools with confirmed cases ... should consider closing if the situation becomes more serious."
Mild cases in U.S., around world
Almost 100 swine flu cases have been identified in 11 U.S. states, but so far, they appear to be mild forms of the disease.
Forty-five cases had been confirmed in New York State alone by the end of Tuesday.
In Europe, Germany and Austria became the third and fourth countries to confirm cases of swine flu on Wednesday, following previously confirmed cases in Britain and Spain.
Swine flu has also been found in several other countries including Canada, the United States and New Zealand.
So far, none of the 19 Canadian cases are believed to be serious.
New Zealand's senior regional health manager, Dr. Julia Peters, said Wednesday that the country has 14 confirmed cases of swine flu, and is testing another 44 suspected cases.
In Egypt, the government ordered the slaughtering of all 300,000 pigs within the country as a precautionary measure.
"It has been decided to immediately start slaughtering all the pigs in Egypt using the full capacity of the country's slaughterhouses," Health Minister Hatem el-Gabaly told reporters Wednesday.
No swine flu cases have been identified in Egypt, though two cases have been reported in neighbouring Israel.
In Switzerland, Fukuda said there was no evidence to suggest people were getting sick from contact with pigs.
With files from The Associated Press
