A South Carolina man who was bitten by mosquitoes while fishing is the year's first U.S. case of West Nile virus, the Associated Press reports.

The man, whose name was withheld by the Centers for Disease Control and Prevention (CDC), is said to be older than 65 and otherwise in good health. He was released from the hospital in June and is improving, reports the AP.

The virus is transmitted when a mosquito bites an infected bird, then bites a person. It normally causes flu-like symptoms, but the virus can be deadly in people with weaker immune systems.

Last year, there were 4,156 U.S. cases of West Nile and 284 deaths, the CDC says.