According to the latest state data, this is the first monkeypox case reported north of the Sacramento area.
The Humboldt County Department of Health and Human Services says the patient is doing well and self-isolating at home.
Humboldt County received 20 vaccines earlier this month, some of which will be used for staff, who will in turn help vaccinate community members. The county has ordered more vaccines, and expects them to arrive soon.
The county also received a shipment of antiviral medication that can be used for individuals with more serious symptoms.
To date, there have been more than 1,200 cases of the virus reported in California, with a majority in Los Angeles and San Francisco.
Health officials in Oregon have reported only 72 cases as of Tuesday, and none have been identified further south than Lane County.
The monkeypox virus spreads through close personal contact. Public health officials recommend practicing good hygiene and avoiding close contact with people showing symptoms.