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Monkeypox Virus - Mpox. ARUP Consult®. Retrieved May 15, 2025, https://arupconsult.com/content/monkeypox

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Monkeypox Virus - Mpox

Last Literature Review: May 2025 Last Update:

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Monkeypox Virus: What the Lab Needs to Know
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Mpox 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 (e.g., 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 or next generation sequencing (NGS) to detect monkeypox virus DNA. In some situations, detection of orthopoxvirus indicates probable mpox. 

For information about the current status of the monkeypox virus, refer to the CDC’s page on the ongoing global outbreak of clade II mpox. 
 

Quick Answers for Clinicians

Where can I find information about the current outbreak of mpox?

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 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.

How is mpox diagnosed?

Mpox is diagnosed through laboratory testing. The recommended laboratory test is a polymerase chain reaction (PCR) assay of a sample collected from an infected lesion.  Next generation sequencing (NGS) can also be used.  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. Probable monkeypox virus infection can be determined with a positive orthopoxvirus test and no suspicion of other recent orthopoxvirus exposure. 

Which other diseases should be considered when evaluating individuals with suspected mpox?

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 and 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.

What is the role of laboratory testing in differentiating types of mpox?

Mpox is caused by two types of monkeypox virus, clade I and clade II, which can be differentiated by the detection of clade-specific monkeypox virus DNA by polymerase chain reaction (PCR) testing or next generation sequencing (NGS).  Clade II mpox, endemic to West Africa, is circulating as part of the global outbreak, and clade I mpox is typically associated with recent travel to Central or East Africa (regions where it is endemic).  Treatment generally does not differ between clade I- and clade II-associated infections.  Clade-specific testing may be available through public health laboratories.

Indications for Testing

Testing may be appropriate in the presence of characteristic signs and symptoms (e.g., 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 of mpox.  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) testing, usually by 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. Probable monkeypox virus infection can be determined with a positive orthopoxvirus test and no suspicion of other recent orthopoxvirus exposure. 

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 Orthopoxvirus/Monkeypox Virus Testing page.

Viral culture and serology tests are not recommended for the diagnosis of mpox.

ARUP Laboratory Tests

References