Small studies in ferrets at the CDC suggest that when compared with seasonal flu, the virus appears to cause more severe disease but also seems to spread less easily.

CNN: CDC: U.S. may need 600 million swine flu vaccine doses

Even though the regular seasonal flu vaccine contains a strain of the A-flu virus group, it will not prevent you from getting sick if you come in contact with the new flu strain.

CNN: CDC: Increase seen in new swine flu strain

The resulting surge of papers revealed that the virus is vulnerable to existing seasonal-flu vaccine and common drugs, allaying fears that mischief-makers would conjure it up and wreak havoc.

ECONOMIST: Flu research and public safety

Scientists believe the H1N1 virus epidemic is no more dangerous than seasonal flu, and schools should act accordingly, Sebelius said.

CNN: Second U.S. death linked to swine flu, officials say

For them, only injections of H1N1 and seasonal flu vaccines are appropriate, since they contain inactivated or dead virus.

CNN: Study: Underlying conditions playing less of role in H1N1

So far this year, however, there's little sign of seasonal flu in the U.S., where nearly all of the circulating flu virus is H1N1, or swine flu, Frieden said.

MSN: Seasonal flu vaccine could run short, CDC says

In Chile and Australia, two countries with many flu cases, she said H1N1 appears to be the dominant strain, "crowding out" the seasonal influenza virus.

CNN: Swine flu 'not stoppable,' World Health Organization says

The virus, which is spread through coughing and sneezing, has symptoms similar to those produced by ordinary seasonal flu - fever, cough, sore throat, aches, chills and fatigue.

BBC: Island 'prepared' for swine flu