Los Angeles County has reported its first instance of a more severe form of Mpox, marking a significant development for local health officials.

The County Public Health Department announced on Thursday that a local resident has been diagnosed with Clade I Mpox. Notably, this individual has no recent history of international travel.

Clade I Mpox is recognized for its increased severity compared to Clade II, which generally results in milder symptoms. Clade II was the predominant strain during the 2022 U.S. outbreak when the virus was still commonly referred to as Monkeypox.

This discovery in a patient without recent travel history has caused concern among health experts. Clade I is typically associated with Central and Eastern Africa, regions that have faced outbreaks in the past few years, and it is thought to spread more readily than Clade II.

This case marks the second instance of Clade I Mpox in Los Angeles County this month, with the other occurring in Long Beach, which operates an independent health department. In contrast, the county has recorded 118 cases of the milder Clade II Mpox so far this year.

Both the L.A. County and Long Beach cases were found in individuals with no recent international travel history—the only two such cases in the U.S.

Both Clade I and II may present with flu-like symptoms and lesions or rash that can be easily spread through close personal contact, including intercourse and massage, or within households where occupants share personal items.

Health officials said the infected adult in L.A. County was hospitalized but is now recovering at home.

The Los Angeles County Department of Public Health is working with the California Department of Public Health and the Centers for Disease Control and Prevention to investigate the case, identify contacts and determine the source of the infection.

“This identification of cases of clade I mpox, which may cause more severe illness than the more common clade II, is concerning,” said Dr. Muntu Davis, L.A. County public health officer. “Early detection, testing and vaccination are vital to controlling the spread of this virus.”

Health officials continue to recommend the two-dose vaccine against Mpox, which protects against both versions of the virus. Vaccination is particularly recommended for gay and bisexual men, transgender and nonbinary individuals, and people living with or at risk of contracting HIV.

The vaccine, officials said, is available at pharmacies and public clinics across the county, and is free for those enrolled in certain public health programs. A full list of providers is available at the county’s Sexual Health Clinics page.