May 20 (HealthDay News) -- Underscoring the belief that the new H1N1 swine flu is no more dangerous than regular flu, U.S. health officials said Tuesday that those hospitalized with the infection who have underlying health problems fare worse than otherwise healthy people who also have been hospitalized.
And that mirrors trends seen with seasonal -- or regular -- flu, officials said.
In an early release of the U.S. Centers for Disease Control and Prevention's journal Morbidity and Mortality Weekly Report, California health authorities assessed 30 people hospitalized for the H1N1 swine flu. One difference between these patients and patients with seasonal flu was their average age. At 27, the swine flu patients were much younger than most patients with seasonal flu who required hospitalization.
Health officials in both the United States and abroad have previously reported that the H1N1 swine flu seems to be targeting teens and young adults, unlike the regular flu, which usually strikes hardest at the elderly and the very young.
Also, about two-thirds of the hospitalized patients in California had at least one underlying medical condition that put them at higher risk for influenza and its complications, Dr. Anne Schuchat, the CDC's interim deputy director for science and public health program, said during an afternoon teleconference. "The most common conditions were chronic lung disease, conditions associated with immunosuppression, chronic heart disease, obesity and pregnancy. There were five pregnant women in this series of patients," she said.
"Although the majority of hospitalized people infected with this new H1N1 virus recovered without complications, certain people did have severe and prolonged disease," Schuchat said. "None of these patients died. There are still some of these patients in the hospital, so we don't know whether they will make it or not."
Meanwhile, the World Health Organization said Tuesday that production of an H1N1 swine flu vaccine could not begin until mid-July at the earliest, which is weeks later than previous estimates. It would then take months before a vaccine would be available, the Associated Press reported.
The reason: swine flu virus isn't growing very fast in laboratories, making it hard for scientists to get the key ingredient they need for a vaccine -- the "seed stock" from the virus, WHO officials said, the AP reported.
Vaccine experts estimated that, under the best of conditions, they could produce nearly 5 billion doses of swine flu vaccine over a year after beginning full-scale production.
The WHO's director-general, Dr. Margaret Chan, said it would be impossible to produce enough vaccine for all 6.8 billion people on the planet -- a potential scenario that could pit rich countries against poorer ones as they bid for the vaccine, the AP said.
WHO officials are meeting this week at their headquarters in Geneva, Switzerland, with representatives from about 30 drug companies to discuss the potential need for a vaccine and how best to produce it.
One factor complicating a decision on a swine flu vaccine is that most flu vaccine companies can only make limited amounts of both seasonal flu vaccine and pandemic vaccine, such as that needed for swine flu, and not at the same time. The producers also can't make large quantities of both types of vaccine because that would exceed manufacturing capacity.
Testing has found that the swine flu virus remains susceptible to two common antiviral drugs, Tamiflu and Relenza, according to the CDC.
In the United States, while most cases of swine flu continue to be no worse than seasonal flu, the death rate from the new H1N1 virus is slightly higher than that seen with seasonal flu, U.S. health officials said Monday.
"Our best estimate right now is that the fatality [rate] is likely a little bit higher than seasonal influenza, but not necessarily substantially higher," Schuchat said.
Schuchat added that the spread of the swine flu is far from over and could continue through the summer. "H1N1 is not going away, despite what you've heard," she said.
On Tuesday, the CDC was reporting 5,469 U.S. cases of swine flu in 48 states, and six deaths. Health officials said a Missouri man with swine flu had died, and testing was being done to see if the disease caused his death. Also, New York City health officials said they were investigating the death of a 16-month-old boy to determine if swine flu was the cause.
The World Health Organization on Tuesday was reporting 9,830 diagnosed cases in 40 countries, including at least 79 deaths, mostly in Mexico, believed to be the source of the outbreak.
The swine flu is a highly unusual mix of swine, bird and human flu viruses. Experts worry that, if the new flu virus mutates, people would have limited immunity to fight the infection.
The CDC is concerned with what will happen as the H1N1 virus moves into the Southern Hemisphere, where the flu season is about to start. The agency is also preparing for the virus' likely return in the fall to the Northern Hemisphere.
SOURCES: May 19, 2009, teleconference with Anne Schuchat, M.D., Interim Deputy Director for Science and Public Health Program, U.S. Centers for Disease Control and Prevention; Associated Press