The number of West African monkeypox cases in the US has risen significantly in the last week to 349. In response, the Centers for Disease Control and Prevention has launched an Emergency Operations Center that will monitor and coordinate the emergency response to monkeypox and mobilize additional personnel and resources. The Center is staffed by 300 CDC staff in collaboration with local, national, and international officials.
The clinical presentation of monkeypox is a prodrome including fever, lymphadenopathy, headache, and muscle aches followed by the development of a characteristic rash culminating in a firm, deep-seated, well-circumscribed, and sometimes umbilicated lesions. The rash usually starts on the face or in the oral cavity and progresses through several synchronized stages on each affected area and concentrates on the face and extremities, including lesions on the palms and soles.
On June 14th the CDC updated and expanded the US monkeypox case definition. This broader definition allows anyone who is suspected of having monkeypox to be tested and appropriate steps to protect the individuals who may have been exposed. The revised clinical and laboratory classification categories of suspected, probable, and confirmed cases also standardize the case reporting through the National Notifiable Diseases Surveillance System (NNDSS) which allows for better tracking of the disease.
The updated case definition is:
| Clinical and laboratory classification | Criteria |
| Suspected | New characteristic rash* OR |
| Meets one of the epidemiologic criteria and has high clinical suspicion† for monkeypox | |
| Probable | No suspicion of other recent Orthopoxvirus exposure (e.g., Vaccinia virus in ACAM2000 vaccination) AND demonstration of the presence of |
| Orthopoxvirus DNA by polymerase chain reaction testing of a clinical specimen OR | |
| Orthopoxvirus using immunohistochemical or electron microscopy testing methods OR | |
| Demonstration of detectable levels of anti-orthopoxvirus IgM antibody during the period of 4–56 days after rash onset | |
| Confirmed | Demonstration of the presence of Monkeypox virus DNA by polymerase chain reaction testing or Next-Generation sequencing of a clinical specimen OR |
| Isolation of Monkeypox virus in culture from a clinical specimen | |
| Epidemiologic classification | |
| Within 21 days of illness onset: | Reports having contact with a person or persons with a similar appearing rash or with a person who has received a diagnosis of confirmed or probable monkeypox OR |
| Had close or intimate in-person contact with persons in a social network experiencing monkeypox infections. This includes MSM who meet partners through an online website, digital application (“app”), or social event (e.g., a bar or party) OR | |
| Traveled, within 21 days of illness onset outside the United States to a country with confirmed cases of monkeypox or where Monkeypox virus is endemic OR | |
| Had contact with a dead or live wild animal or exotic pet that is an African endemic species, or used a product derived from such animals (e.g., game meat, creams, lotions, powders, etc.) | |
| Exclusions | |
| A case might be excluded as a suspected, probable, or confirmed case if: | An alternative diagnosis* can fully explain the illness OR |
| A person with symptoms consistent with monkeypox does not develop a rash within 5 days of illness onset OR | |
| A case where high-quality specimens do not demonstrate the presence of Orthopoxvirus or Monkeypox virus or antibodies to Orthopoxvirus | |
* The characteristic rash associated with monkeypox lesions involves the following: deep-seated and well-circumscribed lesions, often with central umbilication; and lesion progression through specific sequential stages: macules, papules, vesicles, pustules, and scabs. The rash can sometimes be confused with other diseases that are more commonly encountered in clinical practice (e.g., syphilis, herpes, and varicella-zoster). Historically, sporadic accounts of patients co-infected with Monkeypox virus and other infectious agents (e.g., varicella-zoster, syphilis) have been reported; so patients with a characteristic rash should be considered for Monkeypox virus testing, even if tests for other infectious agents are positive.
† Clinical suspicion may exist if lesions consistent with those from more common infections (e.g., syphilis, herpes, and varicella-zoster) co-exist with lesions that may be characteristic of monkeypox.
The CDC has also begun shipping orthopoxvirus tests to five commercial laboratory companies to expand monkeypox testing capacity and access across the country.
More Information on Monkeypox can be found here:
The CDC’s Monkeypox Outbreak 2022: Situation Summary (updated daily) may be found here:
Photo Credit: NHS England High Consequence Infectious Diseases Network