By CBS13 Staff

KNIGHTS LANDING (CBS13) — A mosquito sample in Yolo County has tested positive for the West Nile virus, officials say.

The test, which was confirmed on Wednesday, marks the first positive of the season for Yolo County.

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Sacramento-Yolo Mosquito & Vector Control District says the mosquito sample was collected from the Knights Landing area.

Officials say the test shows West Nile virus activity is already increasing.

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“This year, activity has started earlier than in recent years,” said Gary Goodman, vector control’s district manager, in a statement. “This is a cause for concern, especially as summer is around the corner and we are approaching the hottest months of the year when activity typically intensifies.”

Already this year, a total of 6 mosquito samples and 7 dead birds have tested positive for West Nile virus.

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West Nile virus season often starts in the summer and lasts through the fall. The virus could cause serious – sometimes fatal – illness in some people, but most don’t feel sick while only 1 in 5 develop a fever.