Monkeypox virus

The monkeypox virus (MPV, MPXV, or hMPXV) is a species of double-stranded DNA viruses that cause mpox disease in humans and other mammals. It is a zoonotic virus belonging to the Orthopoxvirus genus, making it closely related to the variola, cowpox, and vaccinia viruses. MPV is oval, with a lipoprotein outer membrane. Its genome is approximately 190 kb. Smallpox and monkeypox viruses are both orthopoxviruses, and the smallpox vaccine is effective against mpox if given within 3–5 years before the disease is contracted. Symptoms of mpox in humans include a rash that forms blisters and then crusts over, fever, and swollen lymph nodes. The virus is transmissible between animals and humans by direct contact to the lesions or via bodily fluids.

The virus was given the name monkeypox virus after being isolated from monkeys, but most of the carriers of this virus are smaller mammals.

The virus is endemic in Central Africa, where infections in humans are relatively frequent. Though there are many natural hosts for the monkeypox virus, the exact reservoirs and how the virus is circulated in nature needs to be studied further.

The monkeypox virus is a zoonotic virus belonging to the genus Orthopoxvirus, which itself is a member of the family Poxviridae (also known as the poxvirus family). Of note, the Orthopoxvirus genus includes the variola virus that prior to eradication via the advent of the smallpox vaccine, was the cause of the infectious human disease known as smallpox. Members of the poxvirus family, include the monkeypox virus itself have been listed by the WHO as diseases with epidemic or pandemic potential. The monkeypox virus is listed as being a potentially high or severe threat pathogen in both the European Union (EU) and the United States of America.

There are two subtypes or clades, clade I historically associated with the Congo Basin and clade II historically associated with West Africa. A global outbreak during 2022–2023 was caused by clade II.

MPV is 96.3% identical to the variola virus in regards to its coding region, but it does differ in parts of the genome which encode for virulence and host range. Through phylogenetic analysis, it was found that MPV is not a direct descendant of the variola virus.

The monkeypox virus, like other poxviruses, is oval, with a lipoprotein outer membrane. The outer membrane protects the enzymes, DNA, and transcription factors of the virus. Typical DNA viruses replicate and express their genome in the nucleus of eukaryotic cells, relying heavily on the host cell's machinery. However, monkeypox viruses rely mostly on proteins encoded in their genome that allow them to replicate in the cytoplasm.

The genome of the monkeypox virus comprises 200 kb of double-stranded DNA coding for 191 proteins. Similar to other poxviruses, the virions of monkey pox have large oval envelopes. Within each virion, there is a core which holds the genome, along with the enzymes that assist in dissolving the protein coat and replication. The center of the genome codes for genes involved in key functions such as viral transcription and assembly; genes located on the extremities of the viral genome are associated more with interactions between the virus and the host cell, such as spike protein characteristics.