About
- Level: Laboratory Advisory
- Audience: Clinical Laboratory Professionals
LOCS message
On November 15, 2024, the first case of clade I mpox was diagnosed in the United States. Three additional cases due to travel were reported in the U.S. since that time. No additional cases have been detected as of February 12, 2025.
The CDC continues to assess the risk of clade I mpox to the U.S. general population as low. However, given the widespread outbreaks in Central and Eastern Africa, additional travel-associated cases may be reported in the U.S.
State, local, and territorial public health authorities should promptly report cases to CDC—including orthopoxvirus generic (i.e., non-variola orthopoxvirus) positive and clade II negative test results from patients with travel history to countries affected by clade I mpox.
Due to mutations that may impact clade-specific PCR tests, laboratories should use a test that targets a viral essential gene (e.g., the CDC non-variola orthopoxvirus (NVO) test). CDC recommends that laboratories using an orthopoxvirus or monkeypox virus (MPXV) generic test without additional clade-specific testing send all orthopoxvirus or MPXV positive clinical specimens for clade-specific testing. If clade-specific testing is not available in a jurisdiction, specimen submission to a capable public health laboratory or to CDC is encouraged. Your state or local health department can coordinate specimen submission to CDC. Expedited clade testing should be performed for mpox cases that have known international travel to countries with clade I mpox cases.
Laboratories using CDC's NVO test that are not performing their own MPXV clade-specific testing should continue submitting the duplicate specimen from patients with positive NVO test results to CDC. Specimens should be submitted to CDC under surveillance OR for Clinical Laboratory Improvement Amendments (CLIA) testing. Some non-CDC laboratories have other options for clade-specific testing (e.g., molecular testing or genetic sequencing). These laboratories should alert their state health department and CDC (poxvirus@cdc.gov) if results indicate detection of clade I MPXV.
Additional guidance:
Refer to HAN Health Update 516 for the most recent CDC clinical and travel guidance on clade I mpox. Clinicians should know mpox symptoms and ask patients about recent travel history and other risk factors for mpox, and consider MPXV testing. Suspected and confirmed cases of clade I mpox should be reported to the local, territorial, and state public health authorities as soon as possible. CDC recommends vaccination to people who are eligible for mpox vaccine, including those who may have a recent MPXV exposure.
Please review the additional resources below for recommendations and resources for clinicians and public health practitioners, health departments, laboratories, and for the public.
We encourage you to share this message widely with your network(s).
Resources
- About Mpox | CDC
- First Case of Clade I Mpox Diagnosed in the United States | HAN
- California Reports First Known U.S. Case of Emerging Mpox Strain | CDPH
- Risk to United States from clade I mpox outbreak in Central and Eastern Africa | CDC
- Prevention Strategies for Mpox, including Vaccinating People at Risk via Sexual Exposure, for U.S. Travelers Visiting Countries with Clade I Mpox Outbreaks | HAN
- Clinical Features of Mpox | CDC
- Mpox Case Definitions | Travel History and Other Risk Factors | CDC
- Diagnostic Testing for Mpox | CDC
- Mpox Case Definitions | CDC
- Interim Clinical Considerations for Use of Vaccine for Mpox Prevention in the United States | CDC
- Mpox Monitoring and Risk Assessment for People Exposed in the Community | CDC
- Test Order | Submitting Specimens to CDC | CDC
- After Hours/Epi-on-Call Contact Lists | CSTE
Contact us
Please use the information below if you have any questions.
- If you are a clinical or public health laboratory professional, contact LOCS.
- For media inquiries, contact the CDC Newsroom.
- For all other questions, contact CDC-INFO.
Thank you,
The Laboratory Outreach Communication System
Laboratory Outreach Communication System (LOCS) | Division of Laboratory Systems (DLS)
Office of Laboratory Systems and Response (OLSR)
Centers for Disease Control and Prevention (CDC)
LOCS@cdc.gov
www.cdc.gov/locs/php/about