Skip Navigation LinksIncrease-in-Introductions-of-Clade-I-Mpox-and-increases-in-Clade-II-Mpox-Within-California Increase in Introductions of Clade I Mpox and increases in Clade II Mpox Within California

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GAVIN NEWSOM
Governor

State of California—Health and Human Services Agency
California Department of Public Health


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​                                           Health Update                                           ​

TO: Healthcare Providers, Commercial Laboratories, and Local Health Departments
Increase in Introductions of Clade I Mpox and increases in Clade II Mpox Within California
6/12/2026



​Key M​essages

  • ​There has been an increase in travel-related introductions of clade I mpox into California and the U.S. in 2026 and clade II mpox cases have increased in California. Increases in clade I community transmission in Western Europe suggest that additional travel-related clade I mpox cases should be expected in California.
    • Clinicians should have a heightened index of suspicion for mpox and particularly for clade I mpox in individuals who report recent international travel or sexual or intimate contact with someone who recently traveled internationally, especially to an area where clade I is circulating.
    • Providers and assistants including cleaning staff should wear full PPE (gloves, gown, goggles, and fit tested N-95 respirator).
    • Mpox testing should be considered for patients with compatible signs and symptoms (PDF), regardless of vaccination status or previous infection.
      • ​Laboratory testing that is positive for orthopoxvirus infection but negative or indeterminate for clade II mpox infection is likely clade I mpox.
    • ​Providers should report suspect or confirmed clade I mpox cases immediately to their local health department and/or CDPH.
    • Mpox vaccination with two doses is recommended for individuals who may be at risk for mpox including immune compromised individuals and is expected to protect against both clade I and clade II mpox or any subclades. 

​Backg​round

Since January 2026, there have been seven travel-related clade I mpox cases reported in California, compared to five total clade I mpox cases in 2024 and 2025 (total 12 confirmed clade I cases in California). Similarly, the U.S. Centers for Disease Control and Prevention (CDC) has reported 25 travel-related cases of clade I mpox since November 2024, more than half which have occurred since March 2026. This increase in introductions of clade I mpox to California are likely a result of increased community transmission in several countries globally, including in Western Europe. Additional travel-related clade I mpox cases in California and the U.S. are expected.

There have also been recent increases in clade II mpox cases reported in California. In 2026, clade II cases are roughly three times the number of cases in previous years.

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

Recommenda​tions

Recommendations for Health Care Providers

  • Mpox should be considered as a differential diagnosis in sexually active patients with rash, lesion(s), or proctitis. Testing is still warranted among vaccinated persons (or those with previous mpox infection) if compatible signs and symptoms (PDF, 1.2MB) are present.

  • Have a heightened index of suspicion for clade I mpox in patients of any age or gender who present with compatible signs and symptoms AND who report recent international travel or sexual contact with someone who recently traveled internationally, especially to an area where clade I is circulating.

    • ​If laboratory testing confirms orthopoxvirus infection but negative or indeterminate for clade II mpox infection, clade I mpox infection is likely and should be reported to your local health department immediately.

  • Providers should report suspect or confirmed clade I mpox cases immediately to their local health department and/or CDPH.  Do not wait for laboratory confirmation.

  • Symptoms among people with prior mpox infection or vaccination are more likely to be mild, and may present with flu-like symptoms, including fevers, chills, lymphadenopathy or malaise, for several days before or simultaneously with development of mpox lesions.

  • Vac​cinate at risk individuals including those traveling to countries where mpox is spreading – and anticipate sexual or intimate contact. See recommendations: Mpox Vaccination. The vaccine is safe for people who are immunocompromised or taking immune suppressing medications.​

Follow  specimen collection guidelines 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-roof 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.

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.

  • Full PPE should be worn 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.

Treatment
There is no treatment specifically approved for mpox. Most cases of mpox are mild and resolve with supportive care and pain management.

For patients with severe or complicated mpox infections, providers are advised to consult their infectious disease providers, CDPH, and the U.S. Centers for Disease Control and Prevention (CDC). Certain therapeutics may be recommended for these patients, as well as for patients with risk factors for disease progression (e.g., severe immunocompromise).

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 (VRDL): (510) 307-8585 or VRDL.Submittal@cdph.ca.gov.

Recommendations for Local Health Departments

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

  • 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

  • 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 

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