West Nile virus cases in the U.S. hit 4,531 as of Tuesday, including 183 deaths, making 2012 the second-worst year ever for the mosquito-borne illness, the Centers for Disease Control and Prevention reported Wednesday.
Cases were up 8% from last week, to 282, including 15 more deaths reported, said Erin Staples, a West Nile expert for the CDC. The numbers don't represent a new wave of mosquito activity, but rather cases slowly working their way through to the CDC, she said. "It's a reporting lag. We're not hearing from our state partners that they're getting a deluge of cases."