Mpox strain that may be more severe and easily spread is found in L.A. County for first time

Two cases of a potentially more severe strain of mpox have been confirmed in Los Angeles County this week.

It’s the first time this particular type of mpox, known as “Clade I,” has been found in the United States among people who had no history of traveling overseas to high-risk areas.

The first case, reported publicly on Tuesday, involved a resident of Long Beach. The second, reported Thursday, was in a Los Angeles County resident. Both patients had to be hospitalized but are now recovering at home, health officials said.

“While the overall risk of … exposure to the public remains low, we are taking this very seriously,” Long Beach Mayor Rex Richardson said in a statement. “This underscores the importance of continued surveillance, early response and vaccination.”

This type of mpox is different from the one that spawned a global outbreak in 2022, which is known as “Clade II.”

Clade I is potentially even more concerning, however, because it may cause more severe illness and spread more easily, “including through close personal contact,” such as massage or cuddling, in addition to sex, the L.A. County Department of Public Health said.

“The identification of cases of Clade I mpox, which may cause more severe illness than the more-common Clade II, is concerning,” L.A. County health officer Dr. Muntu Davis said in a statement Thursday.

The California Department of Public Health said last year that Clade I has historically caused more severe illness than Clade II, but added that “recent infections from Clade I mpox may not be as clinically severe as in previous outbreaks, especially when cases have access to quality medical care.”

Mpox, formerly known as monkeypox, is primarily spread through close, intimate contact, such as through body fluids, sores, shared bedding or shared clothing, as well as kissing, coughing and sneezing, health officials say.

Tell-tale symptoms “include rash or unusual sores that look like pimples or pus-filled blisters on the face, body and genitals, fever, chills, headache, muscle aches or swelling of lymph nodes,” the L.A. County Department of Public Health said. Other symptoms can include a sore throat.

“Anyone who develops an unexplained rash or lesions should avoid sex and intimate contact and seek medical evaluation as soon as possible,” the Long Beach Department of Health and Human Services said.

People should get tested if they have symptoms, officials said. Those who have symptoms should also avoid sex or close contact.

Clade II mpox generally causes mild-to-moderate illness and has been circulating at low levels throughout the United States since 2022, according to the L.A. County Department of Public Health.

There have been 118 cases of Clade II mpox reported to the L.A. County Department of Public Health so far this year.

Before this week, there had been a total of six cases of Clade I mpox in the U.S. — all among people who had recently traveled to areas where this type of mpox is circulating, namely central and eastern Africa. None of those cases was linked to each other, according to the U.S. Centers for Disease Control and Prevention.

The CDC says there have been more than 40,000 cases of Clade I mpox in central and eastern Africa.

In the Democratic Republic of the Congo, one of the countries with confirmed cases, multiple modes of Clade I mpox transmission have been documented, including “contact with infected dead or live wild animals” and “household contact often involving crowded households,” in addition to sexual contact, according to the CDC.

The risk to the general U.S. population in the U.S. from Clade I mpox is considered “low,” the CDC says. The agency classifies the risk to gay and bisexual men who have sex with more than one partner as “low to moderate.”

Travel-associated cases of Clade I mpox have also been found in a number of other regions globally, including Asia, Australia, Europe and South America.

The first Clade I mpox case in the U.S. was reported 11 months ago — in someone in California who had traveled to Africa and received care in San Mateo County, according to the CDC and California Department of Public Health. That person had mild illness, the San Mateo County health department said at the time.

Most people who are infected get better within two to four weeks, the Long Beach Department of Health and Human Services said, “but antiviral treatments may be considered for individuals with or at risk of developing severe illness.”

The two-dose Jynneos vaccine is also available to help prevent the spread of mpox.

Those who only got one dose can get their second doses “no matter how long it’s been since the first dose,” the L.A. County Department of Public Health said.

Vaccines are widely available, and can be found at pharmacies like Walgreens and CVS. People can look up locations to get vaccinated through the vaccine’s manufacturer, Bavarian Nordic. The L.A. County Department of Public Health also maintains a list of vaccination sites.

The vaccine is available to people at higher risk for the illness, including those who were exposed to an infected individual over the last two weeks.

Also eligible for vaccination are gay and bisexual people and other men who have sex with men; transgender, nonbinary or gender-diverse people; people with HIV; people who are eligible or are taking medicine to prevent getting HIV from sex or injection drug use; people traveling to sub-Saharan Africa or areas with Clade I mpox outbreaks; people who plan to attend a commercial sex event or venue, like a sex club or bathhouse; people who have a sex partner at higher risk for getting infected; and anyone else who requests mpox vaccination.

Officials also recommend people with occupational risks for infection, like certain lab workers, also get vaccinated.