WASHINGTON, Oct. 18 (UPI) -- Doctors say the H1N1 strain of influenza, commonly known as swine flu, is more likely to get deep into the lungs than seasonal influenza.

When that happens, patients tend to get viral pneumonia, The Washington Post reported.

The World Health Organization advised doctors to treat serious cases of H1N1 quickly with antiviral drugs and warned hospitals they may get a lot of extremely sick patients this winter.

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The experts said that, as with seasonal flu, most people infected with the H1N1 strain experience only mild illness. But they also stressed differences. While seasonal flu kills the elderly and people with compromised immune systems, H1N1 targets the young."

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