(AP) -- The new swine flu virus lacks genes that made the 1918 pandemic strain so deadly, a U.S. health official said Friday.
CDC flu chief Dr. Nancy Cox said the good news is "we do not see the markers for virulence that were seen in the 1918 virus."
The global flu epidemic early last century was possibly the deadliest outbreak of all time. The virus was an H1N1 strain - different from the H1N1 strain involved in the current outbreak - and struck mostly healthy young adults. Experts estimate it killed about 40 to 50 million people worldwide.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.