Mpox Updates for Clinicians: First Reported Case of Clade I Mpox in the United States
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Cross-posted from: CDC | NCHHSTP
Dear Clinicians,
December 5, 2024
On November 15, 2024, the California Department of Public Health confirmed the first reported case of clade I mpox in the United States. The individual, who sought medical care for mpox symptoms in San Mateo County, had recently traveled to areas in Eastern Africa experiencing clade I mpox transmission.
Consistent with recent travel-associated clade I mpox cases in other countries, the patient has relatively mild illness and is recovering. CDC and the local and state health departments are tracing the individual’s potential contacts; no additional cases in the United States have been detected as of December 5, 2024. A Health Alert Network (HAN) Health Advisory was issued on November 18, 2024, that included recommendations for clinicians and public health practitioners for mpox clinical recognition, diagnosis, testing, prevention, and surveillance.
Given the ongoing global outbreaks of clade I and clade II mpox, we are sharing CDC’s current recommendations to help inform clinical practice for patients at risk for mpox, those with symptoms consistent with mpox, and patients traveling to areas in Africa that are experiencing sustained clade I mpox transmission, including eligibility for mpox vaccine. While the risk to the general population of the United States posed by the clade I mpox outbreak remains low, as providers, you are the country’s first line of defense in preventing the spread of mpox.
Recommendations for Clinicians and Public Health Practitioners
- Discuss mpox prevention and risk reduction strategies with all your patients traveling to countries with ongoing human-to-human transmission of clade I mpox.
- Take a comprehensive sexual health history and discuss your patient’s travel plans, including if your patient anticipates any sexual or direct skin-to-skin contact (e.g., hugging, kissing, massage) with individuals in areas with ongoing mpox clade I transmission.
- Recommend vaccination with the 2-dose JYNNEOS vaccine series to any adult, regardless of gender identity or sexual orientation, if they are traveling to a country where clade I mpox is spreading between people AND they anticipate experiencing any of the following:
- Sex with a new partner
- Sex at a commercial sex venue, like a sex club or bathhouse
- Sex in exchange for money, goods, drugs, or other trade
- Sex in association with a large public event, such as a rave, party, or festival
- Consider mpox as a possible diagnosis in patients with epidemiologic characteristics and lesions or other clinical signs and symptoms consistent with mpox.
Several countries in Central and Eastern Africa, including the Democratic Republic of the Congo and neighboring countries, are experiencing outbreaks of clade I mpox. Travel-associated clade I mpox cases have been reported in countries in Africa, Asia, and Europe (see CDC’s website for an up-to-date list of the countries affected by clade I mpox outbreaks). Clade I mpox has historically caused a higher proportion of people with mpox to get severely ill or die compared to clade II. However, recent data demonstrate that infections from clade I mpox in the current outbreak may not be as clinically severe as in previous outbreaks.
In September 2024, CDC issued a HAN Health Update and an updated Level 2 Travel Health Notice (practice enhanced precautions) for travelers to Central and Eastern Africa to provide recommendations to clinicians and public health practitioners regarding prevention strategies for mpox for U.S. travelers visiting countries with clade I mpox outbreaks, including vaccinating people at risk via sexual exposure.
Because there are several travel-related cases of clade I mpox around the world and an ongoing global outbreak of clade II mpox, please consider a diagnosis of mpox when determining the cause of a rash or other symptoms consistent with mpox presentation. Early symptoms may include fever, malaise, headache, sore throat, or cough, and (in many cases) swollen lymph nodes. Lymphadenopathy is a characteristic feature of mpox, and lymph nodes may swell in the neck (submandibular & cervical), armpits (axillary), or groin (inguinal) and can occur on both sides of the body or just one.
People with mpox infection develop lesionsExit Disclaimer that typically progress from macules to papules, vesicles, pustules, and then scabs. Many recent clade II mpox cases have presented without early symptoms and have only localized lesions rather than a diffuse rash.
CDC has resources to support the diagnosis and management of patients with mpox, including information on clinical features of mpox, diagnostic tests, case reporting, treatment options, and prevention and infection control guidance for healthcare settings. In the ongoing clade II mpox outbreak, HIV infection and other STIs are highly prevalent among people with mpox. People with immunocompromise (e.g., from advanced HIV) are at risk for severe manifestations of mpox; there is treatment guidance specific to persons with, or at risk for, severe manifestations of mpox. All sexually active adults and adolescents in whom mpox is suspected should be evaluated for HIV and other STIs, including syphilis, gonorrhea, and chlamydia, and provided with appropriate care and prevention information.
JYNNEOS is now routinely available in retail pharmacies and clinics. For more information about paying for the mpox vaccine, review CDC’s mpox vaccine coverage fact sheet.
CDC does not recommend that people who have previously been infected with clade II mpox receive mpox vaccination. Because orthopoxviruses (such as monkeypox virus (MPXV), vaccinia virus and variola virus (smallpox)) are so closely related, vaccination or infection with one provides protection against another. For instance, JYNNEOS (a vaccinia virus vaccine) provides protection against both clades of mpox; this same basis was behind the smallpox eradication campaign that utilized vaccinia virus vaccine for smallpox protection. Similarly, the MPXV clades are >95% genetically alike, therefore infection with one would similarly provide protection against the other.
CDC is available as you continue this work and has free tools available as you navigate sexual health care for your patients. If you have questions about mpox or need clinical consultation, please email poxvirus@cdc.gov or for emergencies, call CDC’s 24/7 Emergency Operations Center at 770-488-7100.
In Partnership,
/Jonathan Mermin/
Jonathan Mermin, MD, MPH
Rear Admiral, USPHS (retired)
Director
National Center for HIV, Viral Hepatitis, STD, and TB Prevention
Centers for Disease Control and Prevention
Stay connected:@DrMerminCDC & Connections
/Daniel Jernigan/
Daniel Jernigan, MD, MPH
Director
National Center for Emerging and Zoonotic Infectious Diseases
Centers for Disease Control and Prevention