In fact, all 40 U.S. cases so far have been mild or the patients have recovered, the U.S. Centers for Disease Control and Prevention reported.
And, in absolute numbers, the death toll is still nowhere near the roughly 35,000 lives snatched each year by the regular "garden variety" seasonal flu, Horovitz pointed out.
But could this outbreak morph into something more alarming?
"We just don't know yet," said Dr. Mark Metersky, spokesman for the American College of Chest Physicians and a professor of pulmonary and critical care medicine at the University of Connecticut School of Medicine in Farmington. "It's early in the outbreak."
Metersky pointed to a 1976 outbreak of swine flu that erupted at Fort Dix, N.J., caused a scare, but then quickly petered out with one death.
Perhaps the most disturbing trend in the Mexican outbreak is the fact that it is primarily young adults who are dying. That's not typical, experts said.
"It is usually people who are weakest, at extremes of age, very young and very old who succumb to influenza and this is a little bit scary because this is a pattern we saw in the [flu] pandemic in 1918," Metersky said.
On the upside, there's a good chance that swine flu may not stick around for long in northern climes, at least not this year. "This will probably have seasonality similar to the one of the regular flu," Topham said. He pointed out, however, that the regular winter flu is never quite gone, because as it wanes from the Northern Hemisphere, it re-establishes in the Southern one.
U.S. health officials declared a public health emergency Sunday in response to the swine flu outbreak, and the number of confirmed cases nationwide had doubled by Monday to 40. The 20 new cases all came from the New York City high school that had previously reported eight cases of the infectious disease.
Some of the U.S. cases, all of which so far have been mild, involved people who had recently returned from trips to Mexico.
Meanwhile, in Mexico, believed to be the source of the outbreak, authorities continued to take dramatic steps over the weekend -- including suspending public gatherings -- to try to contain the swine flu outbreak.
U.S. health officials have reported that they have 50 million doses of the antiviral flu medication Tamiflu. A quarter of those doses were being released to states, if needed.
"The benefits of antivirals are twofold," Lillibridge explained. "In treatment, to shorten the illness and promote recovery at an earlier time and to prevent complications. Second, it can be used in prevention. If you have been exposed to someone who has swine flu, [the drugs are] 70 to 90 percent effective if taken early enough."
Steps have also been taken to perhaps devise a vaccine against this strain of swine flu.
Swine flu is a respiratory disease of pigs caused by type A influenza. Swine flu does not normally infect humans. However, human infections do occur, usually after exposure to pigs. Symptoms resemble those of the regular flu, including sore throat, coughing and fever. The strain of swine flu circulating in North America appears to be a combination of pig, bird, and human flu strains, experts say.
What You Can Do
For right now and for the next few days, the only people who need to worry about infection are those who have been in Mexico or those who have been around people who have visited that country, said Dr. Mark Metersky, a spokesman for the American College of Chest Physicians.
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