11/21/2024 CDC Issues Alert for First Case of Clade I Mpox Diagnosed in the United States

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  • Level: Laboratory Advisory
  • Audience: Clinical Laboratory Professionals
LOCS: Laboratory Outreach Communication System

LOCS Message

On November 18, 2024, the U.S. Centers for Disease Control and Prevention (CDC) issued a Health Alert Network (HAN) Health Advisory about the first case of clade I mpox diagnosed in the United States. On November 15, 2024, the California Department of Public Health (CDPH) confirmed the first reported case of clade I mpox in the U.S. from an individual who had recently traveled to areas experiencing clade I monkeypox virus (MPXV) transmission. CDC and the local and state health departments are investigating potential contacts, but the risk of clade I mpox in the U.S. remains low and no additional cases have been detected as of November 21, 2024.

Given the widespread outbreaks in Central and Eastern Africa, additional travel-associated cases may be reported in the U.S. in the future. There is no change to CDC clinical or travel guidance since publication of the HAN Health Update 516. Clinicians should be aware of mpox symptoms, assess travel history and other risk factors when considering MPXV testing. Clinicians should report suspected and confirmed cases of clade I mpox to local, territorial, and state public health authorities as soon as possible. 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. CDC recommends vaccination to people who are eligible for mpox vaccine, including those who may have a recent MPXV exposure.

For laboratories performing mpox testing using an orthopoxvirus or monkeypox virus (MPXV) generic test without any additional clade-specific testing occurring, CDC recommends sending clinical specimens collected from patients who traveled from any country with clade I mpox cases, or had close or intimate contact with symptomatic people from affected countries, to a laboratory that can perform clade-specific testing as quickly as possible. If clade-specific testing is warranted but is not available in a jurisdiction, specimen submission to a public health laboratory with testing capability or to CDC is encouraged. Specimen submission to CDC can be coordinated through your state or local health department. 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 NVO test) as part of a testing strategy to ensure mpox cases are not missed.

Laboratories using CDC's non-variola orthopoxvirus (NVO) test should continue submitting a duplicate specimen to CDC from all patients with positive NVO test results for routine MPXV clade-specific testing if they are not performing clade-specific testing in their laboratory. Laboratories with clade-specific testing available should alert their state health department and CDC (poxvirus@cdc.gov) if results indicate detection of clade I MPXV.

Please review the HAN 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).

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