THURSDAY, June 25, 2009 (HealthDay News) -- An estimated 1 million Americans have been infected with the H1N1 swine flu, which continues to produce mild illness and a fairly quick recovery in patients, U.S. health officials said Thursday.
The estimate is based on mathematical modeling, Lyn Finelli, a flu surveillance official with the U.S. Centers for Disease Control and Prevention, said at a vaccine advisory meeting in Atlanta, the Associated Press reported.
Nearly 28,000 cases -- about half the cases in the world -- have been reported to the CDC, including 3,065 hospitalizations and 127 deaths, the news service said. By comparison, an estimated 15 million to 60 million Americans are infected with the seasonal flu each year, leading to roughly 36,000 deaths.
Meanwhile, the head of the World Health Organization said Thursday that the previously undiscovered virus, which first surfaced in mid-April in Mexico, has yet to show any signs of mutating.
Health officials are closely monitoring the H1N1 swine flu virus as it migrates from the Northern Hemisphere to the Southern Hemisphere, where the flu season is now under way. Scientists are concerned the virus could mutate as it circulates around the world, becoming more virulent and posing a greater health threat.
"The virus is not mutating for the moment, it is stable," Margaret Chan, director general of the World Health Organization, said in Moscow, according to Agence France Press, citing Russian news agency reports.
Still, Chan underscored the need to closely monitor the virus' spread around the globe, adding that it was highly "unpredictable."
The WHO last week formally declared a pandemic, triggered by the rapid spread of the H1N1 virus across North America, Australia, South America, Europe and regions beyond.
What makes the H1N1 strain different from the typical seasonal flu is that about half of the people killed worldwide were young and previously healthy. In contrast, regular forms of the seasonal flu typically prove most lethal to the very young and the elderly.
Late last week, U.S. health officials said that the new H1N1 swine flu continued to spread in some parts of the country, especially in the Northeast, even though flu season is usually over by now.
"The U.S. will likely see [swine] flu activity continue throughout the summer," Dr. Daniel Jernigan, a medical epidemiologist with the CDC's Influenza Division, said during a press conference.
Even though H1N1 swine flu infections continue to be mild, for the most part, health-care workers need to do more to protect themselves from infection by the virus. A small sample of 26 health-care workers found that half became infected while at work, according to a report in the June 19 issue of the CDC's Morbidity and Mortality Weekly Report.
"This includes one case where the exposure was to another ill health-care person," Dr. Michael Bell, the CDC's associate director for infection control, said during a June 18 press conference.
Bell said infection-control procedures need to be taken seriously.
Bell reiterated that the H1N1 swine flu continues to produce relatively mild symptoms in patients, and much has been learned about the precautions that health-care workers need to take since the virus first surfaced in April. "These lessons need to be applied so if something worse comes around we will be prepared to deal with it safely," he said.
For more on swine flu, visit the U.S. Centers for Disease Control and Prevention.