Pasadena has confirmed its first cases of monkeypox, the city’s public health department reported Tuesday.

Four cases were confirmed or deemed “probable” under the Centers for Disease Control and Prevention’s definition, authorities said.

All those infected were adults, officials said. They are recovering and being monitored by Pasadena health officials, according to the department, which operates independently of the Los Angeles County Public Health Department.

“We have been coordinating with our health care partners who are managing cases of monkeypox infections,” said Public Health Director and Health Officer Dr. Ying-Ying Goh in a statement. “We are recommending individual and community mitigation measures to reduce the risk of spread of the monkeypox virus, and we will continue to provide vaccination to eligible populations as quickly as we receive federally-supplied vaccine.”

The cases were announced just after the Los Angeles County Board of Supervisors unanimously ratified a local emergency declaration in response to the swiftly spreading outbreak, two months after the CDC identified the first case of monkeypox in the county.

The county’s vote came on the heels of Gov. Gavin Newsom’s statewide declaration of a State of Emergency on Monday. Both efforts aim to bolster vaccination efforts, even as county authorities warned that monkeypox cases had ballooned to more than 400 countywide.

Monkeypox is still considered rare. It can spread through contact with bodily fluids, sores, shared items — such as clothing and bedding — that have been contaminated with fluids from the sores of a contaminated person, local health officials said. It can be spread through sex, regardless of gender or sexual orientation.

It was discovered in 1958 in monkeys that were used for research. The first human case was discovered in 1970. It’s usually transmitted to humans from infected wild animals in Africa. It’s related to smallpox but far less lethal, experts say.

According to the CDC, it starts with fever, headache, muscle aches, chills and exhaustion. Then infected lesions form on the skin that eventually turn into scabs and fall off. Symptoms usually start within three weeks of exposure. The CDC says, “If someone has flu-like symptoms, they will usually develop a rash 1-4 days later. Monkeypox can be spread from the time symptoms start until the rash has healed, all scabs have fallen off, and a fresh layer of skin has formed.”

Pasadena Public Health Department is still in discussions about a possible health emergency, according to public information officer Lisa Derderian. Long Beach — which, like Pasadena, has its own health department — is considering such a declaration.

The state reported 423 confirmed cases in L.A. County on Tuesday, just ahead of 368 in San Francisco. From there, Riverside County has 33, Long Beach has 19, and 10 were confirmed out of Orange County.

“We will continue to provide vaccination to eligible populations as quickly as we receive federally-supplied vaccine,” Goh said.

With limited supplies available, Pasadena is providing monkeypox vaccines by invitation only to:

• People confirmed by Public Health to have had high- or intermediate-risk contact with someone with monkeypox, as defined by CDC.

• Residents who attended an event/venue where there was high risk of exposure to monkeypox virus through skin-to-skin or sexual contact.

• Gay or bisexual men and transgender people 18 years and older who meet one or more of a series of criteria.

Jill Stewart, Kristy Hutchings and Brennon Dixson contributed to this report.