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FeedbackMpox is caused by an orthopoxvirus that is related to the virus that causes smallpox. Symptoms of mpox include fever, headache, muscle aches, swollen lymph nodes, and a rash that resembles pimples or blisters. Monkeypox virus is spread from person to person through direct contact with rashes, scabs, or body fluids or by respiratory secretions during close contact (eg, kissing, cuddling, or sexual contact). Monkeypox virus may also be spread through contact with shared objects such as linens, towels, or sexual implements. Pregnant individuals may also transmit the virus to a fetus through the placenta. Mpox is diagnosed using a polymerase chain reaction (PCR)-based assay to detect monkeypox virus DNA, or in some situations, orthopoxvirus DNA.
For information about the current status of the monkeypox virus, refer to the CDC’s 2022-2023 Outbreak Cases and Data page.
Quick Answers for Clinicians
The CDC provides detailed information about the current outbreak of mpox on its website. This is the best place to find up-to-date information on this rapidly evolving situation. For information about ARUP’s response to the mpox outbreak, including frequently asked questions about our laboratory testing, refer to ARUP’s Orthopoxvirus/Monkeypox Virus Testing page.
Mpox is diagnosed through laboratory testing. The recommended laboratory test is a polymerase chain reaction (PCR) assay that detects monkeypox virus DNA in a sample collected from an infected lesion. This test may be performed at a state health laboratory (recommended) or a reference laboratory. However, testing specifically for monkeypox virus is not necessary in some circumstances. According to the CDC, “Once results are received from the laboratory, a positive Orthopoxvirus test is considered to meet the case definition for probable Monkeypox virus infection since there are no other circulating Orthopoxviruses within the United States that cause systemic disease. Clinical care and prevention precautions should begin based on the Orthopoxvirus test result and should not wait for any additional viral characterization testing that may be performed.”
Mpox has a similar clinical presentation to several other diseases, particularly sexually transmitted infections. These include infections caused by Treponema pallidum (syphilis) and herpes simplex virus (herpes). Varicella-Zoster virus (the virus that causes chickenpox/shingles), although not sexually transmitted, may resemble mpox in clinical presentation. Bacterial skin infections, scabies, and medication-associated allergies may also cause mpox-like rashes. The diagnosis of a sexually transmitted infection such as syphilis or herpes does not rule out the presence of mpox.
ARUP offers only an orthopoxvirus assay for the diagnosis of mpox. This is in accordance with the CDC’s recommendations for monkeypox virus screening/testing. Given the documented circulation of monkeypox virus in the United States during the current outbreak and the absence of any other orthopoxviruses in circulation, monkeypox virus-specific laboratory testing is not always necessary. Nucleic acid amplification (NAA)-based testing that detects orthopoxvirus DNA is sufficient to meet the case definition of probable mpox infection in the United States.
Indications for Testing
Testing may be appropriate in the presence of characteristic signs and symptoms (eg, rash), when a patient has had contact with someone with confirmed or probable mpox, when a patient has had close or intimate contact with a person in a community with high monkeypox virus activity, or when a patient has traveled to a region with confirmed cases of mpox. For more information, refer to the CDC’s Case Definitions for Use in the 2022 Mpox Response. Clinicians should consult their state health department if an mpox infection or exposure is suspected.
Laboratory Testing
The recommended laboratory test for the diagnosis of mpox is nucleic acid amplification (NAA), usually PCR. The detection of monkeypox virus DNA by PCR or other NAA-based techniques is considered diagnostic. However, testing specifically for mpox is not necessary in some circumstances. According to the CDC, “Once results are received from the laboratory, a positive Orthopoxvirus test is considered to meet the case definition for probable Monkeypox virus infection since there are no other circulating Orthopoxviruses within the United States that cause systemic disease. Clinical care and prevention precautions should begin based on the Orthopoxvirus test result and should not wait for any additional viral characterization testing that may be performed.”
A specimen should be collected from infected or healing lesions.
It is recommended that the specimen be sent to a state health lab for testing, but testing is also available from reference laboratories.
Collection and transportation guidelines may vary based on the performing laboratory. Clinicians should consult their laboratory for specific specimen collection and handling instructions for samples that may be infected with monkeypox virus. The CDC provides detailed information about specimen collection for mpox assays.
More information about ARUP’s specimen collection requirements can be found on ARUP’s Orthopox/Monkeypox Virus Testing page.
Viral culture and serology tests are not recommended for the diagnosis of mpox.
ARUP Laboratory Tests
Qualitative Polymerase Chain Reaction
References
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CDC - Monkeypox: update for clinicians on testing and treatment
Centers for Disease Control and Prevention. Update for clinicians on testing and treatment for monkeypox. Updated Jul 2022; accessed Oct 2023.
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CDC - Mpox: 2022-2023 outbreak cases-data
Centers for Disease Control and Prevention. Mpox: 2022-2023 outbreak cases and data. Updated Sep 2023; accessed Oct 2023.
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CDC - Mpox: case definitions 2022
Centers for Disease Control and Prevention. Mpox: case definitions for use in the 2022 mpox response. Updated Jul 2022; accessed Oct 2023.
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cdc - guidelines-specimens-mpox testing
Centers for Disease Control and Prevention. Guidelines for collecting and handling specimens for mpox testing. Updated Sep 2022; accessed Oct 2023.
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