The Wisconsin researchers also said the H1N1 swine flu virus seems to be closely related to the viruses responsible for the deadly 1918-19 Spanish flu pandemic, a finding that has been reported before. Antibodies taken from patients born before 1920 can recognize the H1N1 swine flu virus, but not so for people born after 1920, the scientists said.
But, the researchers added, all antiviral drugs tested, including Tamiflu, were effective in cell cultures against the new virus, lending support to the use of these drugs as a first line of defense.
Last week, U.S. health officials warned against complacency and said the country should be prepared for the swine flu virus' expected return in the fall.
Health and Human Services Secretary Kathleen Sebelius, Department of Homeland Security Secretary Janet Napolitano, Education Secretary Arne Duncan and others led on Thursday an H1N1 swine flu "preparedness summit" at the National Institutes of Health in Bethesda, Md.
"Scientists and public health experts forecast that the impact of H1N1 may well worsen in the fall -- when the regular flu season hits, or even earlier, when schools start to open -- which is only five or six weeks away in some cases," Sebelius said in a news release.
The H1N1 swine flu first surfaced in the United States in mid-April, and has since infected an estimated 1 million Americans or more. Although the virus continues to produce mild illness and patients recover fairly quickly, 211 people in the United States have died from the disease, according to the U.S. Centers for Disease Control and Prevention.
The most recent figures from the World Health Organization put the number of deaths globally at 429.
Health officials are worried that the H1N1 virus could mutate, becoming more virulent and dangerous.
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