FIRST LOOK: Swine Flu Virus Revealed  

Scientists have snapped the first ever portrait of H1N1, the new swine flu virus that has swept the globe in recent weeks.
A virus cell (such as the H1N1 swine flu cells above) is made up of a core that contains genetic material, which is surrounded by a protein-filled coat that allows the virus to catch onto and invade target cells. Each cell measures about one-ten-thousandth of a millimeter wide.
The samples, obtained from an infected patient in California, were photographed on April 27, 2009, at the U.S. Centers for Disease Control and Prevention's headquarters in Atlanta, Georgia.
(See more swine flu pictures.)
As of May 4, 2009, 286 people have swine flu in the United States, according to the CDC. Twenty countries have seen nearly a thousand instances of swine flu, the World Health Organization reported. (See a map of swine flu's spread.)
The new virus is similar to flu viruses that normally occur in pigs in North America. But H1N1 has genes from European and Asian pigs, as well as from birds and humans, which makes the virus a very different organism, experts say.
No one knows how severe this virus will become, but so far in the U.S. most cases have been mild.
"It's a situation where we should be cautious but not panicky," Susan Rehm, medical director for the National Foundation for Infectious Diseases, said on April 29.
"From what we understand so far, the severity doesn't seem to be much different than what it is in regular seasonal influenza."
—Christine Dell'Amore
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Photograph courtesy CDC Influenza Laboratory