WEDNESDAY, May 6 (HealthDay News) -- While the large majority of U.S. cases of swine flu continue to be mild, those who are hospitalized with more severe disease appear to be atypically young, federal health officials said Wednesday.
The median age of hospitalized individuals with swine flu is 15, which is younger than occurs with regular seasonal flu, Dr. Richard Besser, acting director of the U.S. Centers for Disease Control and Prevention, said during an afternoon news conference.
"We are seeing the same distribution in hospitalized patients as we are in milder cases in the community, and that's younger than what you would see in seasonal flu," Besser said. "In seasonal flu you tend to see a predominance of burden of disease in the elderly and in the very young, and here we are seeing it more in the younger population."
"That is something we are keeping our eye on. That is something that raises concern," he added.
Overall, the age spread for hospitalized patients ranges from 8 months to 53 years of age, Besser said. Why the more severe cases are skewing young remains unclear, he said, but it could be that younger people are getting sicker sooner, or older people may have some kind of built-in immunity.
In any case, the U.S. outbreak of H1N1 swine flu is continuing and, although most cases are still mild, more deaths are expected, Besser said. "We remain concerned," he said. "We are seeing continued spread around the country. We are seeing increases in numbers of patients."
The death earlier this week of a woman in Texas, the first U.S. resident to die from the swine flu, "reminds us that influenza can be a very serious infection, and it's one we need to continue to take very seriously," Besser added.
According to the Associated Press, Texas health officials have not said that the death of 33-year-old schoolteacher Judy Trunnell was directly caused by the H1N1 flu, noting that she also had unspecified "chronic underlying conditions."
Late Tuesday, reports surfaced that the government would ask Americans to get three vaccinations for the upcoming flu season -- one for the seasonal flu and two for this new strain of H1N1. However, on Wednesday Besser said that it was premature to make that decision.
"Before a vaccine is administered there are a series of studies that need to be taken. These are under the direction of the National Institutes of Health and approved by the Food and Drug Administration. They need to do studies to determine how much of the antigen needs to be in the vaccine to stimulate protection," he said.
"They will also need to see -- do you get sufficient immunity from one dose, do you need more than one dose," Besser said. "With each vaccine it's different, with different age groups it's different. It's really early to say how many vaccines someone is going to need until those studies are done," he said. "Hopefully, we will be able to find a vaccine that worked with one dose."
Besser said that, as of Wednesday, the CDC was reporting 1,487 probable and confirmed cases in 44 states. "That's an increase of around 400 from yesterday. There are around 850 probable cases and 642 confirmed cases. The confirmed cases are in 41 states," he said.
In addition, there are 35 confirmed hospitalizations from the flu and an additional 17 probably caused by flu, Besser said. Much of the increase in cases is due to catching up on testing, but there is a real increase in disease too, he said.
Besser noted that in Mexico, the outbreak's epicenter, the flu is disappearing in some areas and popping up in others, which is what will be seen in the United States as well.
"When you see a large outbreak or epidemic it is frequently made up of a series of smaller outbreaks and epidemics. What they are seeing in Mexico is parts of the country where they are seeing increases in disease and in parts of the country they are seeing decreases in disease. When you add that all up it may show some leveling off, but it doesn't give a sense of how dynamic the situation is," he said.
The World Health Organization is now reporting about 1,500 cases of swine flu in 22 countries, with Canada, Spain and the United Kingdom having the most cases outside of Mexico and the United States.
Last week, a 23-month-old boy from Mexico, who also had underlying health problems, died from the swine flu illness in a Houston hospital. He was the first fatality in the United States from the current swine flu outbreak.
On Tuesday, U.S. health officials said the outbreak of swine flu appears similar to the seasonal flu in its severity, so schools across the nation should remain open and any schools that did close should reopen.
This announcement marked a change from the previous guidance, which recommended that affected schools close for at least two weeks. Students who are sick with flu-like symptoms should stay home for at least a week, officials cautioned.
What health experts 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.
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.
And that has led to a boom in sales of the two drugs in the United States, the AP reported. Frightened by the prospects of the swine flu, Americans are snapping up the two antiviral medicines that treat the virus, whether they have it or not.
On Wednesday afternoon, the U.S. Food and Drug Administration said it had approved a new manufacturing facility used to produce influenza vaccines. The facility is approved for seasonal flu vaccine production and could be used to produce vaccine against the new H1N1 swine flu strain.
The facility, located in the United States, is owned and operated by Sanofi Pasteur, and will greatly increase the company's production capability, the FDA said in a news release.
For more on swine flu, visit the U.S. Centers for Disease Control and Prevention.
SOURCES: May 6, 2009, teleconference with Richard Besser, M.D., acting director of the U.S. Centers for Disease Control and Prevention; May 6, 2009, news release, U.S. Food and Drug Administration; May 5, 2009, teleconference with Kathleen Sebelius, secretary, U.S. Department of Health & Human Services, and Richard Besser, M.D., acting director of the U.S. Centers for Disease Control and Prevention; Associated Press; Washington Post