In 2022, 115 countries reported cases of mpox, leading to the declaration of a public health emergency of international concern (PHEIC). In 2024, a second PHEIC was declared based on the increase due to the rise in Monkeypox virus cases. The article “Mpox: current knowledge and understanding—a scoping review” in FEMS Microbiology Reviews discusses the Monkeypox virus, covering its molecular and clinical features, how the virus spreads, as well as recommendations for vaccination, infection control, and treatment. Helen Callaby explains in this #FascinatingMicrobes interview for the #FEMSmicroBlog.
What do we know about the Monkeypox virus?
The Monkeypox virus is a double-stranded DNA virus, in the genus Orthopox virus, which is the same genus that Smallpox belongs to. There are two recognized lineages of this disease-causing virus: clade I, formerly known as the Central African or Congo Basin clade, and clade II, formerly known as the West African clade.
The cases in the 2022 outbreak were similar to clade II or the West African Monkeypox virus isolates. However, it was different enough that the World Health Organization recognized two subclades within clade II: clade IIa and clade IIb. The cases in the 2024 outbreak were associated with the clade I virus.
What is the mpox disease like?
Mpox in humans is a rash illness resulting from infection with Monkeypox virus. Typically, although not in all cases, mpox may first present with a fever followed by enlarged lymph nodes and a rash. The description of the rash varies depending on which clade of the virus a person is infected with.
Mpox is usually diagnosed once the rash is apparent, using a swab from the lesion. Polymerase chain reaction then confirms the presence of Monkeypox virus.
Human cases have been reported in endemic areas for over 50 years. Yet, there was limited understanding of how the virus spreads to humans, the full range of symptoms, and the case fatality rate—especially when comparing the two clades. Some reports suggested that clade I may cause more severe symptoms and outcomes, but this was based on limited data.
How does mpox spread?
Mpox was originally thought to be primarily a zoonotic infection, meaning it spreads from animals to humans. It is now recognised that it can also spread by direct human-to-human contact, including sexual contact. However, it may also be able to spread via objects or other materials that the virus can live on, and possibly through respiratory infections.
There is a lack of research exploring suitable precautions for infection control to prevent transmission. As a precautionary measure, the World Health Organization recommends a respiratory mask for health workers during patient treatment due to the potential airborne transmission.
Is there a vaccine for mpox?
The vaccine we used to eradicate smallpox may also be effective against mpox, since it offers protection against closely related viruses. It is estimated to be nearly 80% effective in protecting against Clade II mpox. Yet, new vaccines are in trial, including mRNA candidates.
How can mpox be treated?
If the disease is mild, then mpox can be managed symptomatically. If it is severe, there are some anti-viral options, such as Tecovirimat, Cidofovir, and Brincidofovir, which may help overcome the viral infection and prevent significant complications. However, we still don’t fully understand how well they work.
Whilst mpox has been recognised as a potentially severe human disease for more than half a century, the two recent outbreaks have highlighted that we still need significant research to better understand this disease. We still lack a clear understanding of how infections by the two clades differ and how the disease progresses.
- Read the article “Mpox: current knowledge and understanding—a scoping review” by Callaby et al. in FEMS Microbiology Reviews (2025).
Helen Callaby is a PhD student on a Wellcome Trust-funded PhD at the University of Dundee, exploring the use of rapid infection diagnostics to optimise antimicrobial use for patients with multimorbidity in Scotland. Her background is as a specialty registrar in Infectious Diseases and Medical Microbiology. She has worked as a Senior Clinical Research Fellow at the Rare and Imported Pathogens Laboratory, Porton Down, during the 2022 Mpox Public Health Emergency of International Concern.
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The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.
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