What the CDC shows is an ecosystem made up of a hub (CDC), multimedia (YouTube) and distribution (Twitter, email etc), all optimized to provide users what they need in a search. 

1. The Main site – http://emergency.cdc.gov/
2. Swine (H1N1) specific site – Swine Flu – http://www.cdc.gov/h1n1flu/
3. Example of collateral – http://www.cdc.gov/h1n1flu/recommendations.htm
4. Multimedia on YouTube – http://www.youtube.com/user/CDCStreamingHealth
5. Distribution/Alerts via Twitter (as well as email, RSS and related tools) – http://twitter.com/CDCemergency

The result is all key properties showing up on page 1 of a Google search for the swine H1N1 flu.  Different search strings do get different results but the CDC results are generally at the top or referred to in other articles at the top.

The search string: http://www.google.com/search?hl=en&safe=off&rls=com.microsoft%3Aen-us%3AIE-SearchBox&rlz=1I7GGLJ_en&q=cdc+swine+flu+h1n1+flu

Sample screen shot: