(AP) — Health officials in Nebraska’s largest county say a 75-year-old man infected with the West Nile virus is their first case this year.

The Douglas County health department said Monday that the unidentified man has been hospitalized. Officials say he traveled recently to an area in Nebraska where mosquito pools have tested positive for the virus, and they believe he was exposed on that trip.

So far this year, no mosquitoes in Douglas County have tested positive for the virus.

Dr. Adi Pour, the county’s health director, says cases are typically reported around this time of year. Officials note that most people who are infected have no symptoms, or experience mild flu-like symptoms. The most vulnerable people are those who are at least 50 years old or have weakened immune systems.