The new swine flu strain lacks traits that made the 1918 pandemic so deadly, US authorities said Friday, amid a 50-state effort to contain the disease and spread prudence, not panic, among the public.
The US Centers for Disease Control and Prevention (CDC) said total confirmed cases of H1N1 influenza in the United States had climbed to 143 across 20 states and that more were expected in the coming weeks.
"I'm optimistic that we are going to be able to manage this effectively, but we still have more work to do," President Barack Obama said as he discussed the government response to the outbreak with his cabinet at the White House.
"We are essentially ensuring that in the worst case scenario we can manage this appropriately," said Obama, who noted that seasonal flu in the United States kills about 36,000 people and forces 200,000 hospitalizations annually.
Amid rampant references to the 1918 influenza outbreak that killed perhaps as many as 50 million people worldwide, officials said the new strain did not appear as deadly.
"We do not see the markers for virulence that were seen in the 1918 virus," Nancy Cox, the chief of the CDC's influenza division, told reporters on a conference call.
But Cox warned there was still "a great deal" that scientists "do not understand" about the 1918 influenza strain, which is thought to have been the deadliest influenza outbreak ever.
The median age of those confirmed ill in the United States was 17, with patients ranging in age from one year old to 81, said acting deputy CDC director Anne Schuchat.
The CDC said research into a vaccine against the new strain was making strides -- though one would likely not be available for months -- and stressed that most US cases had thus far been "relatively mild."
"Thankfully, we are not seeing as much severity as has been reported out of Mexico," acting CDC director Richard Besser said, as authorities south of the border gave an updated confirmed toll of 15 dead and 328 people infected.
US Vice President Joe Biden's home state of Delaware, Illinois, Kentucky, Florida and Virginia were the latest to battle the virus that has also reached into the heart of the US capital.
Officials urged common-sense steps like frequent, careful hand-washing, and said sick people should avoid travel -- but urged the healthy population not to shun restaurants, airplanes, or other crowded areas.
"It's really important that we strike a balance and that we don't do more harm with intervention than this virus is causing," Schuchat told National Public Radio.
Hundreds of schools closed across the country, as the number of suspected cases rose and was expected to climb further in the coming days -- partly because of intense new scrutiny of people with flu symptoms.
"In the next week we're going to hear reports of a lot more cases. We've now got people in every state and every health department working with us to detect these cases," said CDC respiratory disease section chief Cynthia Whitney.
"We're concerned about the possibility of severe cases, and we know there are likely to be some. But the majority of what we have seen so far has been mild, self-limited illness," said Schuchat.
Whitney told CNN there had "been a lot of progress" in research on a vaccine, with scientists selecting strains to go into the inoculation and working to grow them in the vast quantities needed.
"We're very hopeful," she said.
US authorities were still coping with the fallout from Biden's suggestion -- later retracted by his office and the White House -- that the public avoid travel on airplanes and subways.
"A clear message is: If you have the flu or flu-like symptoms, you shouldn't be getting on an airplane, or you shouldn't be getting in a subway. But for the general population, that's quite fine to do," Besser told ABC television.
Continental Airlines Friday announced it would roughly halve its service to Mexico for the month of May, citing low demand.
Prior to the reductions, Continental operated an average of 450 weekly flights to the country.
Only one person has so far died in the United States from the H1N1 flu virus: a Mexican toddler who was visiting relatives in Texas.
The US Marine Corps reported Friday that a total of three marines had contracted the disease.
Source: AFP Global Edition
