Monkeypox virus | |
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Colorized transmission electron micrograph of monkeypox virus particles (teal) found within an infected cell (brown), cultured in the laboratory. | |
Virus classification ![]() | |
(unranked): | Virus |
Realm: | Varidnaviria |
Kingdom: | Bamfordvirae |
Phylum: | Nucleocytoviricota |
Class: | Pokkesviricetes |
Order: | Chitovirales |
Family: | Poxviridae |
Genus: | Orthopoxvirus |
Species: | Monkeypox virus |
Clades | |
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Synonyms | |
MPV, MPXV, hMPXV, [ongoing consideration about changing the virus's name] Contents |
The monkeypox virus (MPV, MPXV, or hMPXV) [1] [lower-alpha 1] is a species of double-stranded DNA virus that causes 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. The 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. [3] Symptoms of mpox in humans include a rash that forms blisters and then crusts over, fever, and swollen lymph nodes. [4] The virus is transmissible between animals and humans by direct contact to the lesions or bodily fluids. [5] The virus was given the name monkeypox virus after being isolated from monkeys, but most of the carriers of this virus are smaller mammals. [4]
The virus is endemic in Central Africa, where infections in humans are relatively frequent. [4] [6] 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. [7]
MPV is part of the genus Orthopoxvirus, belonging to the Poxviridae family, which have been listed by the WHO as diseases with epidemic or pandemic potential. [8] 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. [4]
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. [9] Through phylogenetic analysis, it was found that MPV is not a direct descendant of the variola virus. [9]
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. [10] 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. [11]
The genome of the monkeypox virus comprises 200 kb of double-stranded DNA coding for 191 proteins. [12] [13] 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. [14] 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. [11]
Monkeypox virus is relatively large, compared to other viruses. This makes it harder for the virus to breach the host defences, such as crossing gap junctions. Furthermore, the large size makes it harder for the virus to replicate quickly and evade immune response. [11] To evade host immune systems, and buy more time for replication, monkeypox and other orthopox viruses have evolved mechanisms to evade host immune cells. [15]
![]() | This section may be too technical for most readers to understand.(June 2023) |
As an Orthopoxvirus, MPV replication occurs entirely in the cell cytoplasm within 'factories' – created from the host rough endoplasmic reticulum (ER) – where viral mRNA transcription and translation also take place. [16] [17] The factories are also where DNA replication, gene expression, and assembly of mature virions (MV) are located. [18]
MPV virions (MVs) are able to bind to the cell surface with the help of viral proteins. [19] Virus entry into the host cell plasma membrane is dependent on a neutral pH, otherwise entry occurs via a low-pH dependent endocytic route. [19] The MV of the monkeypox virus has an Entry Fusion Complex (EFC), allowing it to enter the host cell after attachment. [19]
The viral mRNA is translated into structural virion protein by the host ribosomes. [16] Gene expression begins when MPV releases viral proteins and enzymatic factors that disable the cell. [20] Mature virions are infectious. However, they will stay inside the cell until they are transported from the factories to the Golgi/endosomal compartment. [18] Protein synthesis allows for the ER membrane of the factory to dismantle, while small lipid-bilayer membranes will appear to encapsulate the genomes of new virions, now extracellular viruses (EVs). [20] [16] [18] The VPS52 and VPS54 genes of the GARP complex, which is important for transport, are necessary for wrapping the virus, and formation of EVs. [18] DNA concatemers process the genomes, which appear in new virions, along with other enzymes, and genetic information needed for the replication cycle to occur. [20] EVs are necessary for the spread of the virus from cell-to-cell and its long-distance spread. [18]
Zoonotic transmission can occur from direct contact with the blood, bodily fluids, wounds, or mucosal lesions of infected animals whether they are dead or alive. The virus is thought to have originated in Africa where the virus has been observed in multiple animals, including rope squirrels, tree squirrels, Gambian pouched rats, dormice, and different species of monkeys. Though the natural reservoir of the monkeypox virus has not yet been established, rodents are speculated to be the most likely reservoir. Eating meat that has not been properly cooked and consuming other products of infected animals proves to be a major risk factor in the spread of infection. [21]
Monkeypox virus can be transmitted from one person to another through contact with infectious lesion material or fluid on the skin, in the mouth or on the genitals; this includes touching, close contact and during sex. It may also spread by means of respiratory droplets from talking, coughing or sneezing. [4] [23] During the 2022-2023 outbreak, transmission between people was almost exclusively via sexual contact. [24] There is a lower risk of infection from fomites (objects which can become infectious after being touched by an infected person) such as clothing or bedding, but precautions should be taken. [4]
The virus then enters the body through broken skin, or mucosal surfaces such as the mouth, respiratory tract, or genitals. [25] [26]
There are two recorded instances of human to animal transmission. Both occurred during the 2022–2023 global mpox outbreak. In both cases, the owners of a pet dog first became infected with mpox and transmitted the infection to the pet. [27] [26]
Initial symptoms of mpox infection are fever, muscle pains, and sore throat, followed by an itchy or painful rash, headache, swollen lymph nodes, and fatigue. Not everyone will exhibit the complete range of symptoms. [28] [29]
Most mpox patients become symptomatic 4–11 days after infection. However, the incubation period can be as short as one day. The 2022–2023 outbreak revealed that incubation periods of up to 4 weeks are possible, with 5% of cases having incubation periods longer than the previously assumed 21 days. [28] [30]Historically, smallpox vaccine had been reported to reduce the risk of mpox among previously vaccinated persons in Africa. The decrease in immunity to poxviruses in exposed populations is a factor in the increasing prevalence of human mpox. It is attributed to waning cross-protective immunity among those vaccinated before 1980, when mass smallpox vaccinations were discontinued, and to the gradually increasing proportion of unvaccinated individuals. [33]
As of August 2024 there are 4 vaccines in use to prevent mpox, although supplies are limited. All were originally developed to combat smallpox. [34]
The MVA-BN vaccine, originally developed for smallpox, has been approved in the United States for use by persons who are either considered at high risk of exposure to mpox, or who may have recently been exposed to it. [39] [40] [41] The United States Centers for Disease Control and Prevention (CDC) recommends that persons investigating mpox outbreaks, those caring for infected individuals or animals, and those exposed by close or intimate contact with infected individuals or animals should receive a vaccination. [42]
The CDC has made detailed recommendations in addition to the standard precautions for infection control. These include that healthcare providers don a gown, mask, goggles, and a disposable filtering respirator (such as an N95), and that an infected person should be isolated a private room to keep others from possible contact. [43]
Those living in countries where mpox is endemic should avoid contact with sick mammals such as rodents, marsupials, non-human primates (dead or alive) that could harbour Orthopoxvirus monkeypox and should refrain from eating or handling wild game (bush meat). [44] [45]
During the 2022–2023 outbreak, several public health authorities launched public awareness campaigns in order to reduce spread of the disease. [46] [47] [48]Pox viruses have mechanisms to evade the hosts' innate and adaptive immune systems. Viral proteins, expressed by infected cells, employ multiple approaches to limit immune system activity, including binding to, and preventing activation of proteins within the host's immune system, and preventing infected cells from dying to enable them to continue replicating the monkey pox virus. [54]
The virus is subclassified into two clades, clade I and clade II. [4] At the protein level, the clades share 170 orthologs, and their transcriptional regulatory sequences show no significant differences. [8] Both clades have 53 common virulence genes, which contain different types of amino acid changes. 121 of the amino acid changes in the virulence genes are silent, while 61 are conservative, and 93 are non-conservative. [8]
Historically, the case fatality rate (CFR) of past outbreaks was estimated at between 1% and 10%, with clade I considered to be more severe than clade II. [55] The CFR of the 2022-2023 global outbreak (caused by clade IIb) has been very low - estimated at 0.16%, with the majority of deaths in individuals who were already immunocompromised. [56]
Name [57] | Former names [57] | Nations [58] [59] | |
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Clade I | Congo Basin Central African | ||
Clade II | Clade IIa | West African | |
Clade IIb | Widespread globally - See 2022–2023 mpox outbreak § Cases per country and territory |
Monkeypox virus was first identified by Preben von Magnus in Copenhagen, Denmark, in 1958 in crab-eating macaque monkeys (Macaca fascicularis) being used as laboratory animals. [60] The virus was originally given the name monkeypox virus because it had been isolated from monkeys; subsequent research reveals that monkeys are not the main host. Other small mammals in the tropical forests of Central and West Africa [61] are suspected to form a natural reservoir. [8]
The first human infection was diagnosed 1970, in the Democratic Republic of Congo. [4] Small viral outbreaks with secondary human-to-human infection occur routinely in endemic areas of Central Africa; the primary route of infection is thought to be contact with the infected animals or their bodily fluids. [62] The first reported outbreak in humans outside of Africa occurred in 2003 in the United States; it was traced to Gambian pouched rats which had been imported as exotic pets. [63] There have subsequently been a number of outbreaks to regions outside of the endemic areas in Central Africa.
Mpox is an infectious viral disease that can occur in humans and other animals. Symptoms include a rash that forms blisters and then crusts over, fever, and swollen lymph nodes. The illness is usually mild, and most of infected individuals recover within a few weeks without treatment. The time from exposure to the onset of symptoms ranges from five to twenty-one days, and symptoms typically last from two to four weeks. However, cases may be severe, especially in children, pregnant women, or people with suppressed immune systems.
Vaccinia virus is a large, complex, enveloped virus belonging to the poxvirus family. It has a linear, double-stranded DNA genome approximately 190 kbp in length, which encodes approximately 250 genes. The dimensions of the virion are roughly 360 × 270 × 250 nm, with a mass of approximately 5–10 fg. The vaccinia virus is the source of the modern smallpox vaccine, which the World Health Organization (WHO) used to eradicate smallpox in a global vaccination campaign in 1958–1977. Although smallpox no longer exists in the wild, vaccinia virus is still studied widely by scientists as a tool for gene therapy and genetic engineering.
Modified vaccinia Ankara (MVA) is an attenuated (weakened) strain of the vaccinia virus. It is being used as a vaccine against smallpox and mpox, having fewer side effects than smallpox vaccines derived from other poxviruses.
Orthopoxvirus is a genus of viruses in the family Poxviridae and subfamily Chordopoxvirinae. Vertebrates, including mammals and humans, and arthropods serve as natural hosts. There are 12 species in this genus. Diseases associated with this genus include smallpox, cowpox, horsepox, camelpox, and mpox. The most widely known member of the genus is Variola virus, which causes smallpox. It was eradicated globally by 1977, through the use of Vaccinia virus as a vaccine. The most recently described species is the Alaskapox virus, first isolated in 2015.
An outbreak of Monkeypox began in May 2003 in the United States. By July, a total of 71 cases were found in six Midwestern states including Wisconsin, Indiana (16), Illinois (12), Kansas (1), Missouri (2), and Ohio (1). The cause of the outbreak was traced to three species of African rodents imported from Ghana on April 9, 2003, into the United States by an exotic animal importer in Texas. These were shipped from Texas to an Illinois distributor, who housed them with prairie dogs, which then became infected.
In May 2022, the World Health Organization (WHO) made an emergency announcement of the existence of a multi-country outbreak of mpox, a viral disease then commonly known as "monkeypox". The initial cluster of cases was found in the United Kingdom, where the first case was detected in London on 6 May 2022 in a patient with a recent travel history from Nigeria where the disease has been endemic. On 16 May, the UK Health Security Agency (UKHSA) confirmed four new cases with no link to travel to a country where mpox is endemic. Subsequently, cases have been reported from many countries and regions. The outbreak marked the first time mpox had spread widely outside Central and West Africa. The disease had been circulating and evolving in human hosts over several years before the outbreak and was caused by the clade IIb variant of the virus.
The 2022–2023 mpox outbreak in the United Kingdom is part of the larger outbreak of human mpox caused by the West African clade (type) of the monkeypox virus. The United Kingdom was the first country, outside of the endemic African areas, to experience an outbreak. As of 22 July 2022, there were 2,208 confirmed cases in the United Kingdom, with 2,115 in England, 54 in Scotland, 24 in Wales, and 15 in Northern Ireland.
The 2022–2023 mpox outbreak in the United States is part of the larger outbreak of human mpox caused by the West African clade of the monkeypox virus. The United States was the fourth country outside of the African countries with endemic mpox, to experience an outbreak in 2022. The first case was documented in Boston, Massachusetts, on May 17, 2022. As of August 22, mpox has spread to all 50 states in the United States, as well as Washington, D.C., and Puerto Rico. The United States has the highest number of mpox cases in the world. California has the highest number of mpox cases in the United States.
The 2022–2023 mpox outbreak in Canada is a part of the outbreak of human mpox caused by the West African clade of the monkeypox virus. The outbreak started in Canada on May 19, 2022, with the country since then becoming one of the most affected in the Americas.
The 2022–2023 mpox outbreak in Italy is part of the larger outbreak of human mpox caused by the West African clade of the monkeypox virus. Italy was the sixth country, outside of the African countries with endemic mpox, to experience an outbreak in 2022. The first case was documented in Rome, Italy, on May 19, 2022. As of August 5th, Italy has 505 cases.
The 2022 – 2023 mpox outbreak in France is part of the larger outbreak of human mpox caused by the West African clade of the monkeypox virus. France had its first case on 20 May 2022.
The 2022–2023 mpox outbreak in Belgium is part of the larger outbreak of human mpox caused by the West African clade of the monkeypox virus. Belgium was the fifth country, outside of the African countries with endemic mpox, to experience an outbreak in 2022. The first case was documented in Antwerp, Belgium, on 19 May 2022. As of 10 August, Belgium has 546 cases and 1 suspected case.
The 2022–2023 mpox outbreak in Israel is a part of the ongoing outbreak of human mpox caused by the West African clade of the monkeypox virus. The outbreak was first reported in Israel on 20 May 2022 when the Health Ministry announced a suspected case which was confirmed on 21 May 2022. One month later, on 21 June, the first locally transmitted case was reported.
The 2022–2023 mpox outbreak in Switzerland is a part of the outbreak of human mpox caused by the West African clade of the monkeypox virus. The outbreak started in Switzerland on 19 May 2022, with the country since then becoming one of the most affected in Europe.
The 2022–2023 mpox outbreak in Austria is part of the larger outbreak of human mpox caused by the West African clade of the monkeypox virus. Austria is the fifteenth country outside of Africa to experience an endemic mpox outbreak. The first case was reported in Vienna, Austria, on 22 May 2022. As of 2 December, Austria has confirmed a total of 327 cases.
The 2022–2023 mpox outbreak in Mexico is part of the larger outbreak of human mpox caused by the West African clade of the monkeypox virus. Mexico is the twenty-fourth country outside of Africa to experience an endemic mpox outbreak. The first case was reported in Mexico City, Mexico, on May 28, 2022. As of December 8th 2022, Mexico had confirmed a total of 3455 cases in all 32 states and 4 deaths.
The 2022–2023 mpox outbreak in Brazil is a part of the ongoing outbreak of human mpox caused by the West African clade of the monkeypox virus. The outbreak was first reported in Brazil on 9 June 2022 when a man in São Paulo was registered as the country's index case.
The 2022–2023 mpox outbreak in India is a part of the ongoing outbreak of human mpox caused by the West African clade of the monkeypox virus. The outbreak was first reported in India on 14 July 2022 when Kerala's State Health Minister Veena George announced a suspected imported case which was confirmed hours later by the NIV. India was the tenth country to report a mpox case in Asia and the first in South Asia. Currently, India has reported 23 cases of mpox.
The 2022–2023 mpox outbreak in the Netherlands is an ongoing global outbreak which has also spread in the Netherlands. The RIVM declared the disease an A-disease which makes it mandatory to report suspected cases to the GGD. The first human case of mpox in the Netherlands has been identified at the 21 May 2022. The outbreak does have a noticeable impact at the society, especially with people spreading misinformation related to the virus. The ongoing COVID-19 pandemic in the Netherlands has increased the fear among the community for a new pandemic like mpox.
The 2022–2023 mpox outbreak in South Africa is a part of the larger outbreak of human mpox caused by the West African clade of the monkeypox virus. South Africa was the forty-seventh country, outside of the African countries with endemic mpox, to experience an outbreak in 2022. The first case of mpox in South Africa was on June 23, 2022.