Fort Collins confirmed its first human West Nile infection of the season this week after a blood donor tested positive for the mosquito-transmitted virus.

At this point, the southeast Fort Collins donor is asymptomatic, according to county health officials. About 75 percent of people infected with West Nile virus don't develop any symptoms.

Blood donations are screened prior to distribution to ensure recipient safety. Blood donations that test positive for West Nile are discarded and not used for transfusions, county health officials said.

The donor's case is the first West Nile infection of the season in Larimer County, which regularly ranks among the top 10 counties in the nation for West Nile virus.

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