​Key Me​ssages

• Three new unrelated clade I mpox cases have been confirmed in Southern California with no history of recent international travel. Public health investigation indicates that community transmission of clade I mpox within California is occurring among gay, bisexual, and other men who have sex with men and their social networks.  

• At this time, clade I mpox has not been shown to be more transmissible than clade II . Transmission studies are ongoing.

• Clade I mpox transmission can occur through sexual or intimate contact (e.g., massage, cuddling) or shared living spaces or personal items.

• Clade I mpox can be severe. Risk of severe disease and hospitalization are highest for people with weakened immune systems.

• At this time, the overall risk of clade I mpox to the general population in California and the United States continues to be low. 

• Commercial laboratories should retain positive orthopoxvirus specimens and await guidance for further testing from the public health department.

• Mpox vaccination with two doses is recommended for individuals who may be at risk for mpox and is expected to protect against both clade I and clade II mpox or any subclades. Providers should incorporate assessments for mpox risk and vaccination status at all sexual health visits.

• Boosters (third doses) are not recommended at this time.

• Vaccines are available at many chain pharmacies and certain clinics—see Mpox Vaccine Locator.

• Mpox testing should be considered for patients with compatible signs and symptoms (PDF), regardless of vaccination status or previous infection. 
  

​Background

In October 2025, three clade I mpox cases were identified in Southern California who did not report travel history, or contact with one another. This is indicative of community spread of clade I monkeypox virus (MPXV) in California. All prior cases of clade I mpox in California and in the United States have been associated with international travel to areas in which spread of clade I MPXV is ongoing.

As of October 15, all three patients required hospitalization and are recovering with standard medical care. Contact investigation is ongoing.  The California Department of Public Health (CDPH) continues to work closely with local public health departments to conduct enhanced surveillance to detect additional clade I cases. There have also been recent increases in clade II mpox cases reported in California.

At this time, clade I mpox has not been shown to be more transmissible than clade II. Transmission studies are ongoing. Transmission can occur via sexual contact, non-sexual close contact (e.g., massage, cuddling), shared living spaces or personal items. Clade I mpox can be severe. Risk of severe disease and hospitalization are highest for people with weakened immune systems. ​

Recommendations 

Recommendations for Commercial Laboratories

Commercial laboratories should not discard the following California specimens:

• Positive orthopoxvirus (NVO or OPXV) without clade determination

• Positive monkeypoxvirus (MPXV generic) without clade determination

• Positive orthopoxvirus (NVO or OPXV) with indeterminate clade II MPXV

• Positive orthopoxvirus (NVO or OPXV) with a negative clade II MPXV

Commercial laboratories will be contacted by the public health department. Specimens will be directed to either the local public health laboratory or to the CDPH Viral and Rickettsial Disease Laboratory: (510) 307-8585 or VRDL.Submittal@cdph.ca.gov. ​

Recommendations for Healthcare Providers

Mpox guidance including practice recommendations and information on clinical recognition, treatment, and vaccination are outlined in CDPH Health Advisory: Recent Rise of Mpox Cases in California and the Bay Area (8/26/2025). These recommendations apply to both clade I and clade II mpox.

Follow  specimen collection guidelines and your lab submission criteria to collect specimens, from 2 lesions.

• Use 2 sterile synthetic swabs to vigorously swab each lesion, place into appropriate sterile container labeled with anatomic location.

• Do not de-r oof or aspirate lesion(s) due to risk of sharps injury and exposure. 

• Do not use antiseptic or other topicals before swabbing as these can interfere with test results.

Ensure infection control measures are in place for all suspected clade I and II mpox cases at the time of presentation for clinical care.

Infection Control

• Patients with a rash should be roomed promptly and wear appropriate source control as able (e.g., well-fitted face mask and lesions covered with clothing or bandages).

• Healthcare providers and assisting staff should wear full personal protective equipment (PPE) when evaluating someone with mpox symptoms. This includes gloves, a gown, eyewear, and a fit-tested N95 respirator.

• Special precautions, including full PPE, should also be taken when cleaning and disinfecting rooms after a visit.

Home Isolation Recommendations

Any patients being tested for suspected clade I or II mpox should be advised to isolate at home, away from others, pending results.

• Home isolation should continue for the duration of mpox illness, until the rash is healed.

• Isolation, disinfection, and other precautions within the household are recommended. Clade I mpox may spread, including within the household (e.g., through contaminated surfaces or linens).

• Post-exposure prophylaxis (PEP) with JYNNEOS vaccine is recommended for close contacts of people with mpox—including household contacts and recent sexual contacts. PEP can be given within 14 days of last exposure but is most effective when given as soon as possible. See vaccination section below.

Vaccination

The mpox vaccine is expected to be protective against both clade I and clade II mpox and remains the best strategy to protect against complications including severe illness, hospitalization, and death.

To simplify assessment and improve community vaccination coverage among those at increased risk of exposure given current outbreak data, CDPH recommends the mpox vaccine for any person who:

• Is gay, bisexual, or other man who has sex with men or

• Is transgender, nonbinary, or gender-diverse or

• Has HIV, or is taking/eligible for HIV PrEP or doxy PEP or
  

• Was exposed to someone with mpox in the last 14 days or
  

• Is planning to travel to sub-Saharan Africa, the Middle East or a country with a clade I mpox outbreak and anticipates sexual or intimate contact while traveling or
  

• Anticipates attending a commercial sex event or venue (like a sex club or bathhouse) or

• Has a sex partner with any of the above risks or
  

• Requests mpox vaccination, even if they have not disclosed any risks listed above
  

JYNNEOS is covered by Medi-Cal and most private insurers. It is also on the formularies for AIDS Drug Assistance Program (ADAP) and Pre-Exposure Prophylaxis Program (PrEP-AP), which helps cover the cost of medications, certain vaccines, lab tests, and doctor's visits for HIV prevention in eligible Californians.

Mpox vaccines are available at many chain pharmacies and certain clinics—see Mpox Vaccine Locator.​

Recommendations for Local Health Departments

Notify CDPH immediately if clade I mpox is confirmed or suspected. This includes symptomatic patients who:

• History of international travel or close contact to an international traveler in the prior 21 days, or

• History of close contact to a clade I mpox case or
  

• Have preliminary mpox test results that suggest clade I MPXV:

• Positive orthopoxvirus (NVO+, OPXV+) with negative clade II MPXV

• Positive orthopoxvirus (NVO+, OPXV+) with indeterminate clade II MPXV ​