The Centres for Disease Control and Prevention confirmed the first death in California due to monkeypox, CNN reported on Tuesday.
The US Centres for Disease Control and Prevention said the person had a severely weakened immune system and had been hospitalised.
Health officials said people who are severely immunocompromised and may have been infected should seek medical care and treatment early.
Deaths from monkeypox are extremely rare and often affect babies, pregnant women and people with weakened immune systems, such as from HIV.
A person in Harris County, Texas, who had monkeypox died last month, but the virus’ role in that death has not been confirmed.
There have been almost 22,000 cases of probable or confirmed monkeypox reported in the US this year, as of Monday, CDC data shows. California has the most cases: 4,300.