First U.S. monkeypox death confirmed in California as nearly 22,000 cases reported nationwide

California has confirmed the first death due to monkeypox in the United States this year as nearly 22,000 monkeypox cases have been reported nationwide.

The Los Angeles Department of Public Health and the U.S. Centers for Disease Control and Prevention (CDC) confirmed on Monday that a Los Angeles County resident died due to monkeypox infection.

The resident was "severely immunocompromised and had been hospitalized," according to a release of the Los Angeles Department of Public Health.

No further information on the individual such as age, gender or ethnicity was shared by the department, which cited a need to protect "confidentiality and privacy."

Persons severely immunocompromised who suspect they have monkeypox are encouraged to seek medical care and treatment early and remain under the care of a provider during their illness, said the department.

The person's "impaired immune system could not control the virus once it entered his body, the virus multiplied in an uncontained fashion and it likely spread to several organ systems, causing their malfunction," William Schaffner, a professor in the Division of Infectious Diseases at Vanderbilt University Medical Center, told CNN.

This is the first known death from monkeypox reported in the United States.

Last month, a Texas man, who was also described as being severely immunocompromised, died after being diagnosed with monkeypox, but the role that the infection played in his death is still being investigated.

Nearly 22,000 monkeypox cases had been confirmed in the United States as of Monday, according to the latest CDC data. California has the most confirmed cases among U.S. states so far, with 4,300 cases, followed by New York with 3,591 and Florida with 2,193, according to CDC data.

Monkeypox infections are rarely fatal, with most cases resolving within two to four weeks. According to the World Health Organization, the disease has a fatality rate of around 3 to 6 percent.

However, immunocompromised individuals are more likely to experience severe illness when infected, according to the CDC.

Trends in monkeypox cases appear to be leveling off, but the public should not let down their guard, health experts warned.

"We're continuing to see a downward trend in Europe," World Health Organization Director-General Tedros Adhanom Ghebreyesus said last week. "While reported cases from the Americas also declined last week, it's harder to draw firm conclusions about the epidemic in that region. Some countries in the Americas continue to report increasing number of cases and in some there is likely to be underreporting due to stigma and discrimination or a lack of information for those who need it most."

"A downward trend can be the most dangerous time if it opens the door to complacency," he warned.