California confirms first known U.S. case of emerging mpox strain; risk to public 'very low'

California health officials confirmed Saturday the first known case of an emerging mpox strain in the United States, though they say the risk to the general public remains “very low.”

The California Department of Public Health said the first known case of clade I mpox — a different strain of mpox than what has been circulating in the U.S. in recent years — was confirmed in a person who recently traveled to Africa, with the case connected to an ongoing outbreak there.

The person received treatment in San Mateo County and is currently isolating amid their recovery.

“People who had close contact with this individual are being contacted by public health workers, but there is no concern or evidence that mpox clade I is currently spreading between individuals in California or the United States,” the state’s public health department said in an emailed statement Saturday.

What is mpox?

Mpox, formerly called monkeypox, is caused by infection with the monkeypox virus, according to the U.S. Centers for Disease Control and Prevention. The virus is similar to the one that causes smallpox, the CDC says. It is not related to chickenpox.

The disease is zoonotic and can spread from vertebrate animals to humans, though more human-to-human transmissions have been reported in recent years, according to Politico.

What is clade I mpox?

According to the Center for Disease Control, there are two types of mpox, clade I and clade II. Clade I has historically caused a higher number of people with mpox to get severely sick or die compared to clade II.

How does mpox spread?

Mpox is usually passed from rodents and primates to humans through bites, aerosol transmission, or contact with infected fluids.

Person-to-person transmission is usually through close contact with respiratory secretions, inflected skin lesions or recently contaminated objects, according to the WHO.

The California Department of Public Health said the clade I strain of mpox “spreads in a similar manner as clade II mpox, through close (skin-skin), intimate and sexual contact.”

What are the symptoms of mpox?

Mpox symptoms, while similar to smallpox, are less severe, according to WHO. Those infected with mpox often get rashes and other symptoms. Rashes go through several stages, including scabs, before healing, the CDC says.

The emerging mpox strain leads to more severe illnesses than the other, according to the CDC.

"The virus can cause flu-like symptoms and/or a distinct rash that can be bumpy or fluid-filled on the face, body, genitals, arms, and legs. Rash and sores may also be limited to one part of the body," according to a CDPH statement. "Symptoms can start 3 (to) 21 days after​​ exposure."

Who is the risk of contracting mpox in the United States?

The CDC reports a low risk of getting pox in the general population. However, the risk to gay, bisexual, and other men who have sex with men who have more than one sexual partner is assessed as low to moderate in the United States.

What preventative steps can you take?

The California Department of Public Health recommends the following preventative steps to avoid the spread of mpox:

• Getting vaccinated if you may be at risk for mpox.
• Taking precautions if you were exposed to mpox. Get the mpox vaccine before symptoms develop and consider avoiding intimate contact with others for 21 days. Watch yourself for symptoms and get tested if they develop.
• Preventing spread if you have been told you have mpox. Avoid contact with others until the rash is healed, clean and disinfect shared areas at home and notify people who may have been exposed.
• Talking to any sexual partners.
• Avoiding skin-to-skin contact with those who have a rash or sores that look like mpox.
• Not sharing items with someone who has mpox.
• Washing your hands often.
• Protecting yourself when caring for someone with mpox by using masks, gowns and gloves.