This article needs to be updated.(September 2015) |
Arbovirus infection | |
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Tissue infected with the Rift Valley fever virus | |
Specialty | Infectious disease |
Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term arbovirus is a portmanteau word (arthropod-borne virus). [1] Tibovirus (tick-borne virus) is sometimes used to more specifically describe viruses transmitted by ticks, a superorder within the arthropods. [2] Arboviruses can affect both animals (including humans) and plants. [3] In humans, symptoms of arbovirus infection generally occur 3–15 days after exposure to the virus and last three or four days. The most common clinical features of infection are fever, headache, and malaise, but encephalitis and viral hemorrhagic fever may also occur. [4]
The incubation period – the time between when infection occurs and when symptoms appear – varies from virus to virus, but is usually limited between 2 and 15 days for arboviruses. [5] The majority of infections, however, are asymptomatic. [6] Among cases in which symptoms do appear, symptoms tend to be non-specific, resembling a flu-like illness, and are not indicative of a specific causative agent. These symptoms include fever, headache, malaise, rash and fatigue. Rarely, vomiting and hemorrhagic fever may occur. The central nervous system can also be affected by infection, as encephalitis and meningitis are sometimes observed. [7] Prognosis is good for most people, but is poor in those who develop severe symptoms, with up to a 20% mortality rate in this population depending on the virus. The very young, elderly, pregnant women, and people with immune deficiencies are more likely to develop severe symptoms.[ citation needed ]
Arbovirus | Disease(s) | Incubation period | Symptoms | Duration of symptoms | Complications | Case fatality rate | Vector(s) | Primary host(s) | Geographic distribution | Does infection provide lifelong immunity? |
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Dengue virus | Dengue fever | 3–14 days | Asymptomatic in most cases; fever, headache, rash, muscle, and joint pains | 7–10 days | Shock, internal bleeding, and organ damage | <1% with treatment, 1–5% without; about 25% in severe cases | Aedes mosquitoes, especially Aedes aegypti | Humans | Near the equator globally | Varies [note 1] |
Japanese encephalitis virus | Japanese encephalitis | 5–15 days | Asymptomatic in most cases; fever, headache, fatigue, nausea, and vomiting | Encephalitis, seizures, paralysis, coma, and long-term brain damage | 20–30% in encephalitis cases | Culex mosquitoes, especially Culex tritaeniorhynchus | Domestic pigs and wading birds | Southeast and East Asia | Yes | |
Rift Valley fever virus | Rift Valley fever | 2–6 days | Fever, headache, myalgia and liver abnormalities | 4–7 days | Hemorrhagic fever, meningoencephalitis | 1% in humans; in pregnant livestock, 100% fatality rate for fetuses | Culex tritaeniorhynchus and Aedes vexans | Micropteropus pusillus and Hipposideros abae | Eastern, Southern, and Western Africa | Yes |
Tick-borne encephalitis virus | Tick-borne encephalitis | 7–14 days | Fever, headache, muscle pain, nausea, vomiting, meningitis, and encephalitis | Paralysis and long-term brain damage | 1–2% | Ixodes scapularis , Ixodes ricinus , and Ixodes persulcatus | Small rodents | Eastern Europe and Southern Russia | Yes | |
West Nile virus | West Nile fever, encephalitis | 2–15 days | Asymptomatic in most cases; fever, headache, fatigue, nausea, vomiting, rash | 3–6 days | Swollen lymph nodes, meningitis, encephalitis, acute flaccid paralysis | 3–15% in severe cases | Culex mosquitoes | Passerine birds | North America, Europe, West and Central Asia, Oceania, and Africa | Yes |
Yellow fever virus | Yellow fever | 3–6 days | Fever, headache, back pain, loss of appetite, nausea, and vomiting | 3–4 days | Jaundice, liver damage, gastrointestinal bleeding, recurring fever | 3% in general; 20% in cases with severe complications | Aedes mosquitoes, especially Aedes aegypti | Primates | Tropical and subtropical regions of South America and Africa | Yes |
Arboviruses maintain themselves in nature by going through a cycle between a host, an organism that carries the virus, and a vector, an organism that carries and transmits the virus to other organisms. [9] For arboviruses, vectors are commonly mosquitoes, ticks, sandflies [10] and other arthropods that consume the blood of vertebrates for nutritious or developmental purposes. [11] Vertebrates which have their blood consumed act as the hosts, with each vector generally having an affinity for the blood of specific species, making those species the hosts. [12]
Transmission between the vector and the host occurs when the vector feeds on the blood of the vertebrate, wherein the virus that has established an infection in the salivary glands of the vector comes into contact with the host's blood. [13] [14] While the virus is inside the host, it undergoes a process called amplification, where the virus replicates at sufficient levels to induce viremia, a condition in which there are large numbers of virions present in the blood. [15] The abundance of virions in the host's blood allows the host to transmit the virus to other organisms if its blood is consumed by them. When uninfected vectors become infected from feeding, they are then capable of transmitting the virus to uninfected hosts, resuming amplification of virus populations. If viremia is not achieved in a vertebrate, the species can be called a "dead-end host", as the virus cannot be transmitted back to the vector. [16]
An example of this vector-host relationship can be observed in the transmission of the West Nile virus. Female mosquitoes of the genus Culex prefer to consume the blood of passerine birds, making them the hosts of the virus. [17] When these birds are infected, the virus amplifies, potentially infecting multiple mosquitoes that feed on its blood. [15] These infected mosquitoes may go on to further transmit the virus to more birds. If the mosquito is unable to find its preferred food source, it will choose another. Human blood is sometimes consumed, but since the West Nile virus does not replicate that well in mammals, humans are considered a dead-end host. [16] [18]
Person-to-person transmission of arboviruses is not common, but can occur. Blood transfusions, organ transplantation, and the use of blood products can transmit arboviruses if the virus is present in the donor's blood or organs. [19] [20] [21] Because of this, blood and organs are often screened for viruses before being administered. [21] [22] Rarely, vertical transmission, or mother-to-child transmission, has been observed in infected pregnant [23] and breastfeeding women. [24] Exposure to used needles may also transmit arboviruses if they have been used by an infected person or animal. [25] This puts intravenous drug users and healthcare workers at risk for infection in regions where the arbovirus may be spreading in human populations. [21] [23]
This section is missing information about Jamestown Canyon Virus, La Crosse virus, Powassan virus, Eastern equine encephalitis virus, Saint Louis encephalitis, Western equine encephalitis virus, and more.(September 2015) |
Arboviruses are a polyphyletic group, belonging to various viral genera and therefore exhibiting different virologic characteristics.
Arbovirus | Genome type | Genome length | Diameter | Capsid shape | Enveloped? | Viral entry | Replication site | Viral shedding | Infected cell(s) | Genetic variability |
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African swine fever virus | dsDNA | 170-190 kilobases | ~200 nm | Icosahedral | Yes | Endocytosis | Nucleus | Budding | Endothelial cells and red and white blood cells | 22 genotypes |
Chikungunya virus (CHIKV) | +ssRNA | 11.6 kilobases | 60 - 70 nm | Icosahedral | Yes | Membrane fusion | Cell cytoplasm | Budding | Epithelial cells, endothelial cells, primary fibroblasts and macrophages | Three genotypes |
Dengue virus | +ssRNA | ~11,000 nucleobases | ~50 nm | Icosahedral | Yes | Membrane fusion | Cell cytoplasm | Budding | Langerhans and white blood cells | Four serotypes |
Japanese encephalitis virus | +ssRNA | ~11,000 nucleobases | ~50 nm | Icosahedral | Yes | Membrane fusion | Cell cytoplasm | Budding | Five genotypes | |
Rift Valley fever virus | -ssRNA | Spherical | Yes | Cell cytoplasm | Budding | None [note 1] | ||||
Tick-borne encephalitis virus | +ssRNA | ~11,000 nucleobases | 40-50 nm | Icosahedral | Yes | Membrane fusion | Cell cytoplasm | Budding | Neural cells | Five genotypes |
West Nile virus | +ssRNA | ~11,000 nucleobases (11-12 kilo bases) | 45-50 nm | Icosahedral | Yes | Membrane fusion | Cell cytoplasm | Budding | ||
Yellow fever virus | +ssRNA | ~11,000 nucleobases | 40-60 nm | Icosahedral | Yes | Membrane fusion | Cell cytoplasm | Budding | Hepatocytes and white blood cells | |
Zika virus | +ssRNA | 10794 nucleobases | 40 nm | Icosahedral | Yes | Membrane fusion | Cell cytoplasm | Budding |
Preliminary diagnosis of arbovirus infection is usually based on clinical presentations of symptoms, places and dates of travel, activities, and epidemiological history of the location where infection occurred. [26] Definitive diagnosis is typically made in a laboratory by employing some combination of blood tests, particularly immunologic, serologic and/or virologic techniques such as ELISA, [26] [27] complement fixation, [27] polymerase chain reaction, [27] [28] neutralization test, [29] and hemagglutination-inhibition test. [30]
In the past, arboviruses were organized into one of four groups: A, B, C, and D. Group A denoted members of the genus Alphavirus, [31] [32] Group B were members of the genus Flavivirus, [33] and Group C remains as the Group C serogroup of the genus Orthobunyavirus. [34] Group D was renamed in the mid-1950s to the Guama group and is currently the Guama serogroup in the genus Orthobunyavirus. [35] Currently, viruses are jointly classified according to Baltimore classification and a virus-specific system based on standard biological classification. With the exception of the African swine fever virus, which belongs to the Asfarviridae family of viruses, all major clinically important arboviruses belong to one of the following four groups:[ citation needed ]
Vector control measures, especially mosquito control, are essential to reducing the transmission of disease by arboviruses. Habitat control involves draining swamps and removal of other pools of stagnant water (such as old tires, large outdoor potted plants, empty cans, etc.) that often serve as breeding grounds for mosquitoes. Insecticides can be applied in rural and urban areas, inside houses and other buildings, or in outdoor environments. They are often quite effective for controlling arthropod populations, though use of some of these chemicals is controversial, and some organophosphates and organochlorides (such as DDT) have been banned in many countries. Infertile male mosquitoes have been introduced in some areas in order to reduce the breeding rate of relevant mosquito species. Larvicides are also used worldwide in mosquito abatement programs. Temefos is a common mosquito larvicide. [36]
People can also reduce the risk of getting bitten by arthropods by employing personal protective measures such as sleeping under mosquito nets, wearing protective clothing, applying insect repellents such as permethrin and DEET to clothing and exposed skin, and (where possible) avoiding areas known to harbor high arthropod populations. Arboviral encephalitis can be prevented in two major ways: personal protective measures and public health measures to reduce the population of infected mosquitoes. Personal measures include reducing time outdoors particularly in early evening hours, wearing long pants and long sleeved shirts and applying mosquito repellent to exposed skin areas. Public health measures often require spraying of insecticides to kill juvenile (larvae) and adult mosquitoes. [37]
Vaccines are available for the following arboviral diseases:
Vaccines are in development for the following arboviral diseases:
Because the arboviral encephalitides are viral diseases, antibiotics are not an effective form of treatment and no effective antiviral drugs have yet been discovered. Treatment is supportive, attempting to deal with problems such as swelling of the brain, loss of the automatic breathing activity of the brain and other treatable complications like bacterial pneumonia. [1]
The WHO caution against the use of aspirin and ibuprofen as they can increase the risk of bleeding. [47] [48]
Most arboviruses are located in tropical areas, however as a group they have a global distribution. The warm climate conditions found in tropical areas allows for year-round transmission by the arthropod vectors. Other important factors determining geographic distribution of arthropod vectors include rainfall, humidity, and vegetation. [49]
Mapping methods such as GIS and GPS have allowed for spatial and temporal analyses of arboviruses. Tagging cases or breeding sites geographically has allowed for deeper examination of vector transmission. [50]
To see the epidemiology of specific arboviruses, the following resources hold maps, fact sheets, and reports on arboviruses and arboviral epidemics.
Resource | Description | Link |
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World Health Organization | The WHO compiles studies and maps of the distribution, risk factors, and prevention of specific viruses. The WHO also hosts DengueNet, a database which can be queried about Dengue cases. | http://www.who.int/en/ |
CDC ArboNet Dynamic Map | This interactive map is created by USGS using data from the CDC ArboNET. It provides distribution maps of cases in humans and vectors in the United States. | https://web.archive.org/web/20161215234534/http://diseasemaps.usgs.gov/mapviewer/ |
Center for Disease Control ArboCatalog | The ArboCatalog documents probable arboviruses recorded by the Center for Disease Control, and provides detailed information about the viruses. | https://wwwn.cdc.gov/Arbocat/Default.aspx |
Year | Event |
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1800s | Dengue fever epidemics occur globally |
1898–1914 | First large scale effort to prevent arbovirus infection takes place in Florida, Havana, and the Panama Canal Zone |
1901 | First arbovirus, the yellow fever virus, is discovered |
1906 | Dengue fever transmission is discovered |
1936 | Tick-borne encephalitis virus is discovered |
1937 | Yellow fever vaccine is invented |
1937 | West Nile virus is discovered |
1950s | Japanese encephalitis vaccines are invented |
1980s | Insecticide treated mosquito nets are developed |
1999 | West Nile virus reaches the Western Hemisphere |
Late 1900s | Dengue fever spreads globally |
Arboviruses were not known to exist until the rise of modern medicine, with the germ theory and an understanding that viruses were distinct from other microorganisms. The connection between arthropods and disease was not postulated until 1881 when Cuban doctor and scientist Carlos Finlay proposed that yellow fever may be transmitted by mosquitoes instead of human contact, [51] a reality that was verified by Major Walter Reed in 1901. [52] The primary vector, Aedes aegypti , had spread globally from the 15th to the 19th centuries as a result of globalization and the slave trade. [53] This geographic spreading caused dengue fever epidemics throughout the 18th and 19th centuries, [54] and later, in 1906, transmission by the Aedes mosquitoes was confirmed, making yellow fever and dengue fever the first two diseases known to be caused by viruses. [55]
Thomas Milton Rivers published the first clear description of a virus as distinct from a bacterium in 1927. [56] [57] The discovery of the West Nile virus came in 1937, [58] and has since been found in Culex populations [59] causing epidemics throughout Africa, the Middle East, and Europe. The virus was introduced into the Western Hemisphere in 1999, sparking a series of epidemics. [60] During the latter half of the 20th century, Dengue fever reemerged as a global disease, with the virus spreading geographically due to urbanization, population growth, increased international travel, and global warming, [61] and continues to cause at least 50 million infections per year, making Dengue fever the most common and clinically important arboviral disease. [62] [63]
Yellow fever, alongside malaria, was a major obstacle in the construction of the Panama Canal. French supervision of the project in the 1880s was unsuccessful because of these diseases, forcing the abandonment of the project in 1889. [64] During the American effort to construct the canal in the early 1900s, William C. Gorgas, the Chief Sanitary Officer of Havana, was tasked with overseeing the health of the workers. He had past success in eradicating the disease in Florida and Havana by reducing mosquito populations through draining nearby pools of water, cutting grass, applying oil to the edges of ponds and swamps to kill larvae, and capturing adult mosquitoes that remained indoors during the daytime. [65] Joseph Augustin LePrince, the Chief Sanitary Inspector of the Canal Zone, invented the first commercial larvicide, a mixture of carbolic acid, resin, and caustic soda, to be used throughout the Canal Zone. [66] The combined implementation of these sanitation measures led to a dramatic decline in the number of workers dying and the eventual eradication of yellow fever in the Canal Zone as well as the containment of malaria during the 10-year construction period. Because of the success of these methods at preventing disease, they were adopted and improved upon in other regions of the world. [64] [67]
West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. In about 80% of infections people have few or no symptoms. About 20% of people develop a fever, headache, vomiting, or a rash. In less than 1% of people, encephalitis or meningitis occurs, with associated neck stiffness, confusion, or seizures. Recovery may take weeks to months. The risk of death among those in whom the nervous system is affected is about 10 percent.
Flaviviridae is a family of enveloped positive-strand RNA viruses which mainly infect mammals and birds. They are primarily spread through arthropod vectors. The family gets its name from the yellow fever virus; flavus is Latin for "yellow", and yellow fever in turn was named because of its propensity to cause jaundice in victims. There are 89 species in the family divided among four genera. Diseases associated with the group include: hepatitis (hepaciviruses), hemorrhagic syndromes, fatal mucosal disease (pestiviruses), hemorrhagic fever, encephalitis, and the birth defect microcephaly (flaviviruses).
Flavivirus, renamed Orthoflavivirus in 2023, is a genus of positive-strand RNA viruses in the family Flaviviridae. The genus includes the West Nile virus, dengue virus, tick-borne encephalitis virus, yellow fever virus, Zika virus and several other viruses which may cause encephalitis, as well as insect-specific flaviviruses (ISFs) such as cell fusing agent virus (CFAV), Palm Creek virus (PCV), and Parramatta River virus (PaRV). While dual-host flaviviruses can infect vertebrates as well as arthropods, insect-specific flaviviruses are restricted to their competent arthropods. The means by which flaviviruses establish persistent infection in their competent vectors and cause disease in humans depends upon several virus-host interactions, including the intricate interplay between flavivirus-encoded immune antagonists and the host antiviral innate immune effector molecules.
Oropouche fever is a tropical viral infection which can infect humans. It is transmitted by biting midges and mosquitoes, from a natural reservoir which includes sloths, non-human primates, and birds. The disease is named after the region where it was first discovered and isolated in 1955, by the Oropouche River in Trinidad and Tobago. Oropouche fever is caused by the Oropouche virus (OROV), of the Bunyavirales order of viruses.
Viral encephalitis is inflammation of the brain parenchyma, called encephalitis, by a virus. The different forms of viral encephalitis are called viral encephalitides. It is the most common type of encephalitis and often occurs with viral meningitis. Encephalitic viruses first cause infection and replicate outside of the central nervous system (CNS), most reaching the CNS through the circulatory system and a minority from nerve endings toward the CNS. Once in the brain, the virus and the host's inflammatory response disrupt neural function, leading to illness and complications, many of which frequently are neurological in nature, such as impaired motor skills and altered behavior.
Thogotovirus is a genus of enveloped RNA viruses, one of seven genera in the virus family Orthomyxoviridae. Their single-stranded, negative-sense RNA genome has six or seven segments. Thogotoviruses are distinguished from most other orthomyxoviruses by being arboviruses – viruses that are transmitted by arthropods, in this case usually ticks. Thogotoviruses can replicate in both tick cells and vertebrate cells; one subtype has also been isolated from mosquitoes. A consequence of being transmitted by blood-sucking vectors is that the virus must spread systemically in the vertebrate host – unlike influenza viruses, which are transmitted by respiratory droplets and are usually confined to the respiratory system.
The discipline of medical entomology, or public health entomology, and also veterinary entomology is focused upon insects and arthropods that impact human health. Veterinary entomology is included in this category, because many animal diseases can "jump species" and become a human health threat, for example, bovine encephalitis. Medical entomology also includes scientific research on the behavior, ecology, and epidemiology of arthropod disease vectors, and involves a tremendous outreach to the public, including local and state officials and other stake holders in the interest of public safety.
The National Institute of Virology in Pune, India is an Indian virology research institute and part of the Indian Council of Medical Research (ICMR). It was previously known as 'Virus Research Centre' and was founded in collaboration with the Rockefeller Foundation. It has been designated as a WHO H5 reference laboratory for SE Asia region.
Mosquito-borne diseases or mosquito-borne illnesses are diseases caused by bacteria, viruses or parasites transmitted by mosquitoes. Nearly 700 million people contract mosquito-borne illnesses each year, resulting in more than a million deaths.
Rocio viral encephalitis is an epidemic flaviviral disease of humans first observed in São Paulo State, Brazil, in 1975. Low-level enzootic transmission is likely continuing in the epidemic zone, and with increased deforestation and population expansion, additional epidemics caused by Rocio virus are highly probable. If migratory species of birds are, or become involved in, the virus transmission cycle, the competency of a wide variety of mosquito species for transmitting Rocio virus experimentally suggest that the virus may become more widely distributed. The encephalitis outbreak in the western hemisphere caused by West Nile virus, a related flavivirus, highlights the potential for arboviruses to cause severe problems far from their source enzootic foci.
Mayaro virus disease is a mosquito-borne zoonotic pathogen endemic to certain humid forests of tropical South America. Infection with Mayaro virus causes an acute, self-limited dengue-like illness of 3–5 days' duration. The causative virus, abbreviated MAYV, is in the family Togaviridae, and genus Alphavirus. It is closely related to other alphaviruses that produce a dengue-like illness accompanied by long-lasting arthralgia. It is only known to circulate in tropical South America.
Culex quinquefasciatus, commonly known as the southern house mosquito, is a medium-sized mosquito found in tropical and subtropical regions of the world. It is a vector of Wuchereria bancrofti, avian malaria, and arboviruses including St. Louis encephalitis virus, Western equine encephalitis virus, Zika virus and West Nile virus. It is taxonomically regarded as a member of the Culex pipiens species complex. Its genome was sequenced in 2010, and was shown to have 18,883 protein-coding genes.
Transstadial transmission is the persistence of a symbiont or pathogen in an organism from one life stage ("stadium") to the next, such as larva to nymph to adult. This type of transmission is typically observed in insects. For example, the bacterium Borrelia burgdorferi, the causative agent for Lyme disease, infects the tick vector as a larva, with the infection maintained as the tick molts to a nymph and later develops as an adult. Transstadial transmission is also seen with other microbes such as other bacteria, fungi, and viruses in numerous insects. In addition to ticks, mites are another common vector. Transstadial transmission is especially relevant to public health, as several threats to public health are maintained in insect populations by transstadial transmission. Some debate exists regarding the classification of transstadial transmission as vertical transmission versus horizontal transmission. Reasons for this stem from further debate regarding transovarial transmission, described as the passage of a symbiont or pathogen from an infected female to its progeny, especially in eggs.
Patricia (Pat) Anne Nuttall, OBE is a British virologist and acarologist known for her research on tick-borne diseases. Her discoveries include the fact that pathogens can be transmitted between vectors feeding on a host without being detectable in the host's blood. She is also a science administrator who served as the director of the Natural Environment Research Council (NERC) Centre for Ecology & Hydrology (2001–11). As of 2015, she is professor of arbovirology in the Department of Zoology of the University of Oxford.
Jamestown Canyon encephalitis is an infectious disease caused by the Jamestown Canyon virus, an orthobunyavirus of the California serogroup. It is mainly spread during the summer by different mosquito species in the United States and Canada.
Spondweni virus is an arbovirus, or arthropod-borne virus, which is a member of the family Flaviviridae and the genus Flavivirus. It is part of the Spondweni serogroup which consists of the Sponweni virus and the Zika virus (ZIKV). The Spondweni virus was first isolated in Nigeria in 1952, and ever since, SPONV transmission and activity have been reported throughout Africa. Its primary vector of transmission is the sylvatic mosquito Aedes circumluteolus, though it has been isolated from several different types of mosquito. Transmission of the virus into humans can lead to a viral infection known as Spondweni fever, with symptoms that include headache, nausea, myalgia and arthralgia. However, as SPONV is phylogenetically close to the ZIKV, it is commonly misdiagnosed as ZIKV along with other viral illnesses.
Royal Farm virus, previously known as Karshi virus, was not viewed as pathogenic or harmful to humans. Although infected people suffer with fever-like symptoms, some people in Uzbekistan have reported with severe disease such as encephalitis and other large outbreaks of fever illness connected infection with the virus.
West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family Flaviviridae, from the genus Flavivirus, which also contains the Zika virus, dengue virus, and yellow fever virus. The virus is primarily transmitted by mosquitoes, mostly species of Culex. The primary hosts of WNV are birds, so that the virus remains within a "bird–mosquito–bird" transmission cycle. The virus is genetically related to the Japanese encephalitis family of viruses. Humans and horses both exhibit disease symptoms from the virus, and symptoms rarely occur in other animals.
Sepik virus (SEPV) is an arthropod-borne virus (arbovirus) of the genus Flavivirus and family Flaviviridae. Flaviviridae is one of the most well characterized viral families, as it contains many well-known viruses that cause diseases that have become very prevalent in the world, like Dengue virus. The genus Flavivirus is one of the largest viral genera and encompasses over 50 viral species, including tick and mosquito borne viruses like Yellow fever virus and West Nile virus. Sepik virus is much less well known and has not been as well-classified as other viruses because it has not been known of for very long. Sepik virus was first isolated in 1966 from the mosquito Mansoniaseptempunctata, and it derives its name from the Sepik River area in Papua New Guinea, where it was first found. The geographic range of Sepik virus is limited to Papua New Guinea, due to its isolation.
Global climate change has increased the occurrence of some infectious diseases. Infectious diseases whose transmission is impacted by climate change include, for example, vector-borne diseases like dengue fever, malaria, tick-borne diseases, leishmaniasis, zika fever, chikungunya and Ebola. One mechanism contributing to increased disease transmission is that climate change is altering the geographic range and seasonality of the insects that can carry the diseases. Scientists stated a clear observation in 2022: "The occurrence of climate-related food-borne and waterborne diseases has increased ."