MONDAY, May 4, 2009 (HealthDay News) -- The number of confirmed swine flu cases in the United States climbed Monday to 286 in 36 states. But, the revised numbers indicate catching up on a backlog of lab tests, and not a sudden rise in new infections, federal health officials said.
And, while insisting that "we are not out of the woods," Dr. Richard Besser, acting director of the U.S. Centers for Disease Control and Prevention, said during an afternoon teleconference that "we are seeing a lot of encouraging signs."
Among the encouraging signs: "So far the severity of illness we are seeing in this country is very similar to what we see with seasonal flu," Besser said. "And that's encouraging information."
In addition, some of the initial lab tests are heartening, Besser said. "The lack of some of the factors that have been associated with more severe disease in previous pandemics, we are not seeing those."
Testing for the virus is also becoming faster, Besser said. "We have distributed test kits to every state and this will allow for more rapid diagnosis at the state level," he said.
And, he added, "The situation in Mexico is encouraging. It appears that things are leveling off in Mexico."
On Monday in Mexico -- believed to be the source of the swine flu outbreak -- officials declared the epidemic to be waning. They scaled back their flu alert, saying they would allow cafes, museums and libraries to reopen this week after a five-day shutdown of nonessential businesses. Inspections of schools must be finished before students can return to class, the Associated Press reported.
Officials from the World Health Organization said it was premature for countries to ease up on efforts to control the outbreak, but added that there were no imminent plans to raise the pandemic alert level.
What U.S. officials don't know is whether the never-before-seen virus will return, perhaps in a more dangerous form, when the regular flu season begins again late this year. Because the pathogen is a genetic mix of pig, bird and human flu strains, health officials are worried that humans may have no natural immunity to it.
Besser said Monday that the CDC continues to work to prepare a vaccine, although "the decision doesn't need to be made now whether to manufacture a vaccine" for the next flu season.
Federal health officials will be looking for clues to what the swine flu virus -- officially designated H1N1 -- will do in the fall by monitoring what happens in the Southern Hemisphere, where the flu season there is just getting under way. "That will tell us a lot about whether the virus is changing, whether it's becoming more severe and what measures we might want to take in the fall," he said.
Besser said Monday that there were more than "700 probable cases in a total of 44 states. This likely represents an underestimation of the total number of cases taking place across the country."
The World Health Organization reported Monday that the disease continues to spread around the globe, with 20 countries reporting 985 confirmed cases. Mexico heads the list of countries with 590 laboratory-confirmed cases of infection, including 25 deaths. The United States is next on the list with 226 confirmed human cases, including one death -- a 23-month-old Mexican boy who had traveled to Houston last month for medical treatment.
Currently, the WHO has labeled the outbreak a Phase 5 outbreak, meaning the disease is spreading throughout communities in at least two countries in one of WHO's six regions -- in this case the United States and Mexico. To reach Phase 6, the geographic spread of the disease would have to occur in at least one other country in another region.
Mexican officials on Monday lowered the country's health alert level from red -- or "high" -- to orange -- or "elevated," CNN reported.
"The measures we have taken, and above all the public's reaction, have led to an improvement," Mexico City Mayor Marcelo Ebrard said at a news conference. "But I insist that the virus is still present, that we need to remain on alert, and the resumption of activities will be little by little, not all at once."
As with the previously tested strains of the swine flu virus, new testing has found that the pathogen remains susceptible to the two common antiviral drugs Tamiflu and Relenza, according to the CDC.
Since schools are the focus of many of the outbreaks, the CDC has issued revised recommendations for school closings.
Because children may shed the virus longer than adults, the agency is now recommending that affected schools remain closed for two weeks instead of one, Dr. Anne Schuchat, interim deputy director for the CDC's science and public health program, said during a teleconference on Saturday.
The U.S. Education Department has said that more than 430 schools had closed, affecting about 245,000 children.
St. Francis Preparatory School, the Catholic school that was at the center of swine flu reports in New York City last week, reopened for classes on Monday after being shuttered for a week. City Health Commissioner Dr. Thomas Frieden said there were 73 confirmed cases of swine flu in the city and six probable cases awaiting diagnosis. Almost all the patients have ties to St. Francis, a few have ties to Mexico, and three cases have no known link to either, Frieden said, The New York Times reported.
In a strange twist on Saturday, swine flu was discovered for the first time during this outbreak in pigs. WHO officials reported that the virus had been detected in sick pigs on a farm in Alberta, Canada.
Until now, it was not known whether the virus could infect pigs, even though its genetic makeup clearly points to pigs as the source of the pathogen. However, in this case a human appears to have infected the livestock, not the other way around, the WHO reported. A worker on the farm had traveled to Mexico, come back to Canada and fallen ill.
WHO officials stressed that the swine flu cannot be transmitted through the consumption of pork products.
For more on swine flu, visit the U.S. Centers for Disease Control and Prevention.