On April 14, 2026, the first clade I mpox case in San Francisco (SF) was confirmed. The case occurred in an unvaccinated adult who was hospitalized and is improving. The individual reported close contact with someone who traveled internationally to an area where clade I mpox is circulating.

Clade I mpox is distinct from clade II mpox. The mpox outbreak in the United States that began in 2022 is due to clade II mpox and has led to 1066 cases in SF as of April 9, 2026. In contrast, an outbreak of clade I mpox in Central and Eastern Africa has been ongoing since 2023, with sporadic travel-associated cases reported in non-endemic countries and increasing reports of locally-acquired clade I mpox in Europe. Over the last two years, 15 clade I mpox cases have been reported in the United States, including 6 in California. Public health officials are monitoring cases to determine if clade I mpox is more severe than clade II mpox in the United States.

The patient, who had not received the mpox vaccine, was hospitalized and is improving, according to SFPDH.

The agency said that this clade I mpox patient had reported close contact with another person who had traveled internationally.

The Centers for Disease Control and Prevention said that until now, 15 cases of clade I mpox have been detected in the U.S. since late 2024. Over a quarter of these cases were diagnosed in March 2026 alone.

According to the CDC, all U.S. cases of clade I mpox — which are not linked — were in people who had either recently traveled to areas associated with the outbreak in Central and Eastern Africa or parts of Western Europe with more recent outbreaks, or, like the San Francisco case, were linked to travel.

The Hawai‘i Department of Health is reporting a wastewater sample from O‘ahu that has tested positive for clade I mpox. The sample was collected on April 13, 2026, from a wastewater treatment facility on Joint Base Pearl Harbor Hickam. This is the first time clade I mpox has been detected in wastewater in Hawaiʻi. To date, no clinical case of clade I mpox has been identified in Hawai‘i.

At this time, the risk for the general public is low. The presence of clade I mpox virus in wastewater does not confirm a clinical case or community spread. Instead, it serves as an indicator to be alert for possible mpox cases. People at higher risk of mpox infection should consider being vaccinated with two doses of the JYNNEOS (mpox) vaccine if not already protected.

The JBPHH facility serves not only on-base military housing and facilities, but public sites that receive large numbers of residents and visitors, including the Pearl Harbor National Memorial Museum.

DOH was notified of the initial detection on April 20, 2026, with positive confirmatory results received on April 24, 2026.