Health officials on swine flu: "Not out of woods yet"

Priests — some in masks — pray during a Mass celebrated without the presence of faithful at the

Health officials around the world are cautioning that despite encouraging signs, swine flu still poses a very real threat.

Worldwide, laboratories now have confirmed 898 human cases of the new swine flu in 18 countries, according to the World Health Organization. Swine flu has become widespread in the United States, with 226 cases in 30 states and more expected to turn up in additional states in the next few days, federal health officials said Sunday.

"I think it's circulating all over the U.S. The virus has arrived, I would say, in most of the country now," said Dr. Anne Schuchat, the interim deputy director for science and public health at the Centers for Disease Control and Prevention (CDC).

"The good news is when we look at this virus right now, we're not seeing some of the things in the virus that have been associated in the past with more severe flu. That's encouraging, but it doesn't mean we're out of the woods yet," said Dr. Richard Besser, acting CDC chief.

Schuchat said the virus, called H1N1 by scientists, had a number of unusual features that made it cause for concern. It has flared up at a time of year when the flu season is normally ending. It is new, so people probably have little or no resistance to it.

And unlike the common types of seasonal flu, it appears to infect an unusually high percentage of young people, the median age being 17.

"Most experts would agree that the current outbreak that we are experiencing is mild to moderate in severity," Dr. Jon Andrus of the Pan American Health Organization said in a teleconference from Washington. "That is not to say that things cannot change very rapidly and very dramatically."

Under one scenario, the virus could peter out now, only to roar back in the fall when flu seasons begins. Flu season in the Southern Hemisphere is about to begin, and U.S. authorities will watch how the swine flu circulates there over the coming months as they prepare the first vaccine and then decide whether to order that large amounts of it be produced in the fall.

Production of regular winter flu vaccine is going full-tilt, "to make sure we kind of clear the decks," Health and Human Services Secretary Kathleen Sebelius said Sunday on NBC News' "Meet the Press."

"We are testing the virus strain for H1N1 virus so that we're ready to go into production later, in a month or two, when we make sure that we have the right dosage and the right tests. So we'll be ready for both," she said.

Schuchat said scientists at the CDC were preparing a "seed stock" from virus samples that could be used for a vaccine.

Outside the Americas, the country with the most cases is Spain, with 44. All but four involved people who had recently traveled to Mexico, and all are recovering, the Spanish Health Ministry said.

Mexico's swine-flu outbreak probably peaked last week, and patients are responding well to antiviral treatments, Health Minister Jose Cordova said yesterday in Mexico City. The virus has been confirmed in 23 of Mexico's 31 states and the capital district.