Health Advisory: Mpox Caused by Human Transmission in the Democratic Republic of the Congo

December 12, 2023

Action Requested 

• Be aware that CDC has issued an advisory regarding the occurrence, geographic spread, and sexually associated human-to-human transmission of Clade I Monkeypox virus (MPXV) in the Democratic Republic of the Congo (DRC). 
  • MPXV has two distinct genetic clades (subtypes), and cases of Clade I MPXV have not been reported in the U.S. at this time. However, clinicians should be aware of the possibility of Clade I MPXV in travelers who have been in DRC.
• If a patient in Snohomish County has mpox-like symptoms, which may include a diffuse rash and lymphadenopathy, and recent travel to DRC, clinicians should notify the Snohomish County Health Department immediately. 
  • Call 425-339-3503 to reach the Communicable Disease program by phone.
  • Please complete and fax the Communicable Disease Report Form (PDF) and any accompanying lab reports to 425-339-8706. 
• Submit lesion specimens for clade-specific testing.
• Encourage vaccination for patients who are eligible, as vaccination uptake remains low in the U.S. 
  • Vaccines (e.g., JYNNEOS, ACAM2000) and other medical countermeasures (e.g., tecovirimat, brincidofovir, and vaccinia immune globulin intravenous) are available and expected to be effective for both Clade I and Clade II MPXV infections.
  • Vaccination with JYNNEOS or ACAM2000 or prior MPXV infection should provide antibodies that will provide cross-protection to other orthopoxviruses, including Clade I MPXV. The Advisory Committee on Immunization Practices (ACIP) recommends that people ≥18 years of age with risk factors for mpox be vaccinated, before an exposure, with two doses of the JYNNEOS vaccine 28 days apart unless they were previously infected with mpox or already received two doses. There is no recommendation regarding vaccination for travelers who do not otherwise meet the eligibility criteria. 
  • Eligible patients who have only received one dose of the JYNNEOS vaccine should receive the second dose as soon as possible, regardless of the amount of time that has elapsed since the first dose.
• Continue to consider mpox when evaluating the cause of rashes. Mpox lesions may be small, firm and rubbery, deep-seated, and well-circumscribed, or they may be large, with diffuse, centrifugal lesion distribution. Lymphadenopathy may also be present.
  • During the Clade II outbreak, among people with severe immunocompromise (e.g., due to advanced HIV with CD4 <200 or solid organ transplantation), rash lesions have generally been diffusely distributed, appearing large, necrotic, and fungating (i.e., appearing or progressing like a fungal infection). 
  • Consideration of mpox should be heightened in patients who have epidemiologic characteristics supportive of mpox (including travel from mpox-endemic regions such as DRC within 21 days of illness onset).
• For patients with travel to DRC within 21 days of illness onset, CDC recommends that clinicians pursue MPXV clade-specific testing starting with a consultation with state health departments for testing options (e.g., molecular testing or genetic sequencing). 
  • Contact the Snohomish County Health Department Communicable Disease Program at 425-339-3503 if you have questions about testing.  
  • CDC recommends clinicians follow specimen collection guidelines (including collection of two swabs per lesion) to ensure specimen availability for testing. Unroofing or aspiration of lesions or otherwise using sharp instruments for mpox testing is not recommended due to the risk of sharps injury. 
• Contact the Health Department promptly for any mpox cases for which severe manifestations might occur. Tecovirimat is available through the STOMP trial and Investigational New Drug (IND) protocol.
• Healthcare personnel who evaluate and provide care to patients with mpox and laboratory personnel should continue to follow existing CDC guidance on infection prevention and control for mpox. These are effective in minimizing transmission.

Background

MPXV has two distinct genetic clades (subtypes of MPXV), I and II, which are endemic to central and west Africa, respectively. Clade IIb MPXV has been associated with the 2022-23 global outbreak that has predominately affected gay, bisexual, and other men who have sex with men (MSM). Clade I MPXV is capable of human-to-human spread but has previously been associated with non-sexual routes of transmission; and Clade I has previously been observed to be more transmissible and to cause more severe infections than Clade II. Since January 1, 2023, DRC has reported 12,569 suspected mpox cases (i.e., clinically diagnosed but not laboratory-confirmed) and 581 deaths (5% of suspected mpox cases). This is a substantial increase from the median 3,767 suspected mpox cases reported annually in DRC during the years 2016-2021. Clade I MPXV has been confirmed among cases for which testing was conducted. A recent World Health Organization (WHO) report noted that mpox cases in 2023 have been reported in more DRC provinces than in previous years (i.e., 22 of 26 provinces). This includes cases in urban settings where mpox does not normally occur (Kinshasa and South Kivu Province). In two provinces, outbreaks of Clade I MPXV associated with sexual contact, including among MSM, have been reported for the first time in DRC. Mpox vaccination is not generally available in DRC.

As part of surveillance for viral variants in the United States, CDC has tested a subset of positive MPXV or orthopoxvirus cases from commercial and state laboratories and performed clade-specific testing for 150 cases in 2023 (~12% of U.S. cases); no Clade I MPXV infections have been detected thus far. There are no direct commercial passenger flights from DRC to the United States, and the current threat for Clade I MPXV in travelers remains low. Clade II MPXV infections continue to occur in the United States. CDC encourages U.S. clinicians to continue to be alert for patients presenting with lesions consistent with mpox. Suspicion for Clade I MPXV should be high for people with travel to DRC within 21 days of illness onset, and clade-specific testing of MPXV should be performed in specimens from suspect mpox case-patients who report recent travel to DRC.

Most patients who have recovered from mpox (including infection with Clade II MPXV) or have been vaccinated with JYNNEOS or ACAM2000 are expected to have cross-protection to Clade I MPXV. However, clinicians are recommended to consider mpox as a possible diagnosis if a consistent clinical presentation occurs, even in those who are vaccinated or were previously diagnosed with mpox.

See full CDC HAN Advisory for additional information

Additional Resources

• Mpox Clinical Recognition and Vaccine Information for Healthcare Providers: Information For Healthcare Professionals | Mpox | Poxvirus | CDC
• Mpox Information for the Public: Your Health | Mpox | Poxvirus | CDC
• Biosafety and Select Agent Considerations: Laboratory Procedures | Mpox | Poxvirus | CDC
• Diagnostic Specimen Packaging and Shipping: Transporting Infectious Substances Safely.pdf (dot.gov)