April 2010 H1N1 activity has slowed in the US, except for an upsurge in cases in several southeastern states. Officials are monitoring the situation, as this may or may not be the beginning of a third wave of the virus. The Centers for Disease Control continues to urge people to be vaccinated for H1N1. About 1 in 4 people have been vaccinated. South Dakota leads the nation in the rate of vaccination at 34%.