MONDAY, May 18, 2009 (HealthDay News) -- 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," Dr. Anne Schuchat, the U.S. Centers for Disease Control and Prevention's interim deputy director for science and public health program, said during an afternoon teleconference.
In addition, unlike seasonal flu, which typically strikes hardest at the very young and the elderly, the new H1N1 swine flu is largely affecting children, teens and young adults, with more hospitalizations of younger people, Schuchat said.
"The hospitalizations that we are tracking have this disproportionate occurrence among younger persons," she said. "That's very unusual to have so many people under 20 requiring hospitalization in some of those intensive-care units."
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.
The heat and humidity of summer months are less conducive to the spread of influenza virus, Schuchat said. "This is certainly a possibility -- it's not something I can predict. Most years, the seasonal influenza strains have very reduced circulation in the summer months. Unfortunately, we don't know if we are going to get a break this summer with this [H1N1] virus."
On Sunday night, an assistant principal at a New York City public school became the sixth person in the United States to die from the disease that was first identified last month. On Monday, ABC News rep[orted that New York City health officials announced the closure of three more school buildings for Tuesday, bringing the total number of schools closed due to swine flu to 16.
Health officials said Sunday that the death was not surprising, because even a normal flu season kills an estimated 36,000 Americans every year, and all signs suggest that swine flu causes mild cases of infection and the vast majority of patients recover quickly and fully.
The assistant principal, Mitchell Wiener, who worked at an intermediate school in Queens, had a history of medical problems that might have left him vulnerable to complications from swine flu. His family said he had gout, but the condition was being controlled with medication, The New York Times reported.
New York City's health commissioner, Dr. Thomas R. Frieden, who was just selected Friday by President Barack Obama to lead the Centers for Disease Control and Prevention, said, "We are now seeing a rising tide of flu in many parts of New York City." But he added: "Nothing we've seen so far suggests that it [swine flu] is more dangerous to someone who gets it than the flu that comes every year. We should not forget that the flu that comes every year kills about 1,000 New Yorkers," the Times reported.
Hours before Wiener's death, city officials announced that five more Queens schools had been closed. Wiener's school is one of eight schools temporarily shuttered in New York City by the city health department due to concerns about swine flu, CNN reported.
On Monday, the CDC was reporting 5,123 U.S. cases of swine flu in 48 states, and six deaths. For the most part, the infections continue to be mild and recovery is fairly quick.
The World Health Organization on Monday was reporting 8,480 diagnosed cases in 39 countries, including at least 75 deaths, mostly in Mexico, believed to be the source of the outbreak.
Testing has found that the swine flu virus remains susceptible to two common antiviral drugs, Tamiflu and Relenza, according to the CDC.
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 this new 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.
Meanwhile, the World Health Organization opened its annual meeting Monday in Geneva, Switzerland, with swine flu and the possibility of a vaccine dominating the agenda, the Associated Press reported.
The WHO's director-general, Dr. Margaret Chan, was expected to review experts' recommendations on which companies should produce a vaccine, how much they should make and how it could best be distributed, the news service said.
One factor complicating a decision 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, the AP said.
The WHO estimates up to 2 billion doses of swine flu vaccine could be produced yearly, though the first batches would not be available for four to six months.
Also Monday, health officials were examining new swine flu cases in Spain, Great Britain and especially Japan, where more than 130 people -- most of them teenagers -- have been infected, prompting the government to close 2,000 schools and cancel public events. Many of the new cases were transmitted in-country, meaning those infected had not traveled overseas recently, the AP said.
On Friday, U.S. health officials said the true number of swine flu infections could be higher than 100,000 nationwide.
Dr. Daniel Jernigan, of the CDC's Influenza Division, said that "estimates of the confirmed and probable cases in the United States is probably not the best indicator of transmission at this point. The outbreak is not localized, but is spreading and appears to be expanding throughout the United States. This is an ongoing public health threat."
It's difficult to estimate the number of people who may be infected with swine flu, Jernigan said, "but if we had to make an estimate, I would say that the amount of activity we are seeing with our influenza-like illness network is probably upwards of 100,000."
Jernigan said there also seemed to be more cases of flu generally in the United States -- both the seasonal and the H1N1 swine flu -- than is usually seen at this time of the year.
For more on swine flu, visit the U.S. Centers for Disease Control and Prevention.