The World Health Organization said the outbreak is moving closer to becoming a full-scale pandemic.
Dr. Keiji Fukuda, the organization's top flu expert, told reporters in Geneva that the latest developments are moving the agency closer to raising its pandemic alert to phase 5, indicating widespread human-to-human transmission. That's just one step below level 6, a full-fledged pandemic.
In Washington, Homeland Security Secretary Janet Napolitano was questioned closely by senators about whether the U.S. should close its border with Mexico, where the outbreak apparently began and the casualties have been the greatest. She repeated the administration's position that questioning of people at borders and ports of entry was sufficient for now and said closing borders "has not been merited by the facts."
Dr. Richard Besser, the acting chief of the Centers for Disease Control and Prevention, said in Atlanta there were confirmed cases in ten states, with 51 in New York, 16 in Texas and 14 in California. Two cases have been confirmed in Kansas, Massachusetts and Michigan, while single cases have been reported in Arizona, Indiana, Nevada and Ohio.
State officials in Maine said laboratory tests had confirmed three cases in that state, although those had not yet been included in the CDC count.
In a possible outbreak north of the Mexican border, the commandant of the Marine Corps said a Marine in southern California might have the illness and 39 Marines were being confined on their California base until tests come back.
Marine General James Conway told a Pentagon briefing an initial test indicated the sick Marine -- who was not identified -- might have /*swine flu*/ but his illness did not appear life-threatening.
Obama said he wanted to extend "my thoughts and prayers" to the family of a nearly two-year-old Mexican boy who died in Houston, the first confirmed U.S. fatality among more than five dozen infections. Health officials in Texas said the child had traveled with his family on April 4 from Mexico to Brownsville, had become ill there and was hospitalized before being brought to Houston where he died Monday night.
Texas called off all public high school athletic and academic competitions at least until May 11 due to the outbreak.
"This is obviously a serious situation," and "we are closely and continuously monitoring" it, Obama said of the spreading illness.
Those sentiments were echoed by the Senate's top Republican. "This is a very worrisome situation and we're all following it very closely," said Minority Leader Mitch McConnell of Kentucky. "We stand ready to closely work with the administration to protect the American people as this situation unfolds."
Laboratory testing shows the new virus is treatable by the anti-flu drugs Tamiflu and Relenza, and the first shipments from a federal stockpile arrived Wednesday in New York City and several other locations. The government was shipping to states enough medication to treat 11 million people as a precaution. All states should get their share by May 3.
No shortages have been reported anywhere. There's plenty in regular pharmacies, federal health officials said.
Meanwhile, Egypt's government ordered the slaughter of all pigs in the country as a precaution, though no swine flu cases have been reported there. Egypt's overwhelmingly Muslim population does not eat pork, but farmers raise some 300,000-350,000 pigs for the Christian minority.
The disease is not spread by eating pork, and farmers were to be allowed to sell the meat from the slaughtered animals.
In fact, officials appeared to go out of their way on Wednesday to not call the strain "swine flu." Obama called the bug the "H1N1 virus."
"The disease is not a food-borne illness," Rear Adm. Anne Schuchat, CDC's interim science and public health deputy direct, told the Senate Homeland Security Committee.
She said the strain is particularly worrisome because "it's a virus that hasn't been around before. The general population doesn't have immunity from it."
People have various levels of protection against other more common types of flu because they are exposed to it over time, and that protection accumulates. She suggested that some older people might have more resistance to this particular strain than younger people because its traits might resemble outbreaks of decades ago.
Germany and Austria became the latest countries to report swine flu infections. Germany reported four cases on Wednesday, Austria one case.
New Zealand's total rose to 14. Britain had earlier reported five cases, Spain four. There were 13 cases in Canada and two in Israel.
Obama said it is the recommendation of public health officials that authorities at schools with confirmed or suspected cases of swine flu "should strongly consider temporarily closing so that we can be as safe as possible."
He was underscoring advice that the CDC provided earlier to cities and states, and that some schools -- most prominently in New York City -- already have followed.
"If the situation becomes more serious and we have to take more extensive steps, then parents should also think about contingencies if schools in their areas do temporarily shut down, figuring out and planning what their child care situation would be," Obama advised.
Former Kansas Gov. Kathleen Sebelius, on her first full day as health and human services secretary, said school closings cause "a large ripple effect."
"What happens to the parents? Where do those children go? Do you close the day care center if a younger sibling is there?" Sebelius asked at a briefing for reporters.
Obama advised people to take their own precautions -- washing hands, staying home if they are sick, and keeping sick kids home.
Obama said the federal government is "prepared to do whatever is necessary to control the impact of this virus." He noted his request for $1.5 billion in emergency funding to ensure adequate supplies of vaccines.
CDC for days has said people with flulike symptoms should stay home -- but now also is stressing that other family members should consider staying home or at least limiting how much they go out until they're sure they didn't catch it.
Besser, the acting CDC director, called it "an abundance of caution," but stressed that it's voluntary and that the government hasn't urged actual quarantine, which isn't really effective with flu.