"The critical thing we need to find out is how much it's varying right now," Shaw explained. "Whenever a virus comes into a population it is going to start evolving fairly quickly, as it sort of adapts itself to a new host. That's going to be very important for selecting vaccine strain."
So far, researchers have seen very little variation, "which is kind of typical for an outbreak situation," Shaw said. That's because "a virus comes in and spreads very rapidly and it hasn't had a whole lot of time to change. That's what we are seeing in this case, which indicates to us that this is truly new."
When the virus samples first come in to the lab, they are handled by researchers wearing special protective clothing, face masks and double gloves. Shaw says the virus is "actually easily inactivated by detergents, soaps, alcohol. You wouldn't think so given how it is spread, but it is an easily inactivated virus."
Once inactivated, the samples are brought to a different lab, where scientists are studying the genetic make-up of the virus. They have found virtually no difference between the strain circulating in Mexico and the strain in the U.S. So the virus alone cannot explain the disparity in deaths.
"Something is different, we haven't figured out what yet," Shaw said. "It is not the virus, apparently, it is something else"
CDC scientists are also doing the critical initial work necessary for vaccine development, including trying to grow the virus. At first, that effort was not going well. "We were getting very, I won't say discouraged, but disappointed at first because it took several days before we could get one growing," Shaw said. "But now we're, we have over a dozen growing."
The scientists hope to have a key ingredient ready to send out to potential vaccine manufacturers in the next week. What's critical, Shaw said, is to find a strain that "looks typical of what's out there. That will give the most protection."
Any vaccine, though, will take months to make. The government said today one could be ready for testing by this fall.
U.S. government health officials have said for years now that it was inevitable that a potential pandemic flu virus would appear. Still, in many ways, this virus has caught them by surprise.
"The main thing it points out," said Shaw, "is regardless how we study what happened in the past, every new situation is truly new and different. This one was a total surprise coming out of Mexico. The assumption was it would come out of Asia, a larger population for variants to appear and of course we've been following the (Asian) avian influenza very carefully."
"This one just came out of nowhere."