The flu continues to spread across the US, with elevated activity in nearly every state.

The CDC estimates there have been at least 3.7 million flu cases so far this season, 32,000 of which required hospitalization. Nearly 2,000 people have died, including 19 children.

Four antiviral medications are available, including Tamiflu and Xofluza. All have been shown to be effective against 99 percent of flu viruses tested.

Most people getting sick are infected with a strain called B/Victoria, which usually doesn’t pop up until the end of flu season. Those viruses tend to strike children and young adults more often, but anyone can be affected. In general, B strains are less likely than A strains to cause severe infections. There’s also evidence now that A strains are increasing.