Oropouche fever | |
---|---|
Midges ( Culicoides sp.) are the main vectors which spread the Oropouche virus between humans. [1] | |
Specialty | Infectious diseases |
Symptoms | Fever (~100%), headache (70–80%), arthralgia, myalgia, nausea, vomiting, dizziness, photophobia, rash |
Complications | Meningoencephalitis |
Usual onset | 3–8 days |
Duration | 2–7 days |
Causes | Oropouche virus (OROV) |
Diagnostic method | Clinical, laboratory (PCR) |
Differential diagnosis | Dengue, Chikungunya, Zika, yellow fever, malaria |
Treatment | Symptomatic; none specific |
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. [2] The disease is named after the region where it was first discovered and isolated in 1955, by the Oropouche River in Trinidad and Tobago. [3] Oropouche fever is caused by the Oropouche virus (OROV), of the Bunyavirales order of viruses.
Oropouche fever is endemic to the Amazon basin, with some evidence that its range may be spreading more widely in South and Central America. [4] Since its discovery in 1955, there have been more than 30 epidemics of OROV in countries including Brazil, Peru, and Panama, with over half a million diagnosed cases in total. [5] It has also been detected in-between epidemics, indicating that it may spread silently. [2]
The signs and symptoms of Oropouche fever are similar to those of dengue, chikungunya, and Zika. [6] Symptoms are often mild and typically begin three to eight days after infection. Fever, headache, and muscle and joint pains are most common; a skin rash, unusual sensitivity to light, and nausea and vomiting may also occur. Most cases are self-limited, with recovery in two to seven days. In severe illness, however, the central nervous system may be affected, with symptoms of meningitis and encephalitis, and a tendency to excessive bleeding has been reported in up to 15% of cases. [6]
Oropouche has been recognized as among the most neglected of tropical diseases and as an emerging infectious disease. Little is known about its epidemiology, pathogenesis, and natural history, and there is no specific treatment or vaccine. [6] [7]
Oropouche fever is characterized as an acute febrile illness, meaning that it begins with a sudden onset of a fever followed by other clinical symptoms. [8] It typically takes four to eight days from the incubation period to first start noticing signs of infection, beginning from the bite of the infected mosquito or midge. [9]
Fevers are the most common symptom, occurring in nearly all cases, with temperatures as high as 40 °C (104 °F). Other symptoms include chills, headache, muscle and joint pain (myalgia and arthralgia), dizziness, photophobia, nausea, vomiting, joint pains, epigastric pain, and rashes. [10] As in dengue, a skin rash resembling rubella, conjunctival injection, and pain behind the eyes may occur. [9] The initial febrile episode typically resolves within seven days, but it is very common to have a reccurrence of these symptoms with a lesser intensity. [9] Studies have shown this typically happens in about 60% of cases. [9] Fatigue and weakness may also persist for up to a month after infection. [8] [6]
In serious cases, particularly in large outbreaks, the central nervous system may be affected with symptoms of meningitis and encephalitis, including severe headache, dizziness, neck stiffness, double vision, darting of the eyes, uncoordinated movements, and evidence of viral infection in the cerebrospinal fluid (CSF). [6] A tendency to abnormal bleeding has been reported in up to 15% of cases. [6]
in July 2024, the Brazilian Ministry of Health released a report of four cases of microcephaly in newborns of infected mothers. [11] Fetal deaths were observed possibly associated with vertical transmission, i.e. from mother to child. [12]
Oropouche orthobunyavirus | |
---|---|
Virus classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Negarnaviricota |
Class: | Ellioviricetes |
Order: | Bunyavirales |
Family: | Peribunyaviridae |
Genus: | Orthobunyavirus |
Species: | Oropouche orthobunyavirus |
The oropouche virus is an emerging infectious agent which causes the illness oropouche fever. [13] This virus is an arbovirus and is transmitted among sloths, marsupials, primates, and birds through mosquito species including Aedes serratus and Culex quinquefasciatus . [1] The oropouche virus has evolved to an urban cycle infecting humans though a midge, Culicoides paraensis , as its main transporting vector, [1] with mosquitoes such as Culex quinquefasciatus also possibly contributing. [14]
OROV was first described in Trinidad in 1955 when the prototype strain was isolated from the blood of a febrile human patient and from Coquillettidia venezuelensis mosquitoes. [3] In Brazil, OROV was first described in 1960 when it was isolated from a three-toed sloth ( Bradypus tridactylus ) and Ochlerotatus serratus mosquitoes captured nearby during the construction of the Belém–Brasília Highway. [3]
This section needs to be updated.(August 2024) |
Large epidemics are common and very swift, one of the earliest and largest having occurred at the city of Belém, in the Brazilian Amazon state of Pará, with 11,000 recorded cases. In the Brazilian Amazon, oropouche is the second most frequent viral disease, after dengue fever. Several epidemics have generated more than 263,000 cases, of which half occurred in the period from 1978 to 1980. [15] It is estimated that more than half a million cases have occurred since in Brazil alone, with most having gone undiagnosed or misdiagnosed due to limited availability of laboratory methods for diagnosis (which are expensive and time-consuming), the clinical similarity of Oropouche fever to other more prevalent arboviral illnesses, and the fact that in many cases there may be co-infection with other similar mosquito-borne viruses. [1]
The oropouche virus is responsible for causing massive, explosive outbreaks in Latin American countries, making oropouche fever the second most common arboviral infection seen in Brazil. [16] So far the only reported cases of Oropouche fever have been in Brazil, Panama, Peru, Bolivia, Colombia, Cuba, and Trinidad and Tobago. [9] [17] As of late July 2024, cases in Brazil have surged from 832 in 2023 to 7,284. [18] Two deaths have been reported, both in non-pregnant women who were otherwise healthy. [14]
ORO fever occurs mainly during the rainy seasons, because there is an increase in breeding sites in the vector populations. [9] There has also been reports of the oropouche epidemics during the dry season but this is most likely due to the high population density of mosquitoes from the past rainy season. [9]
Oropouche fever is caused by the oropouche virus (OROV).
There is not a significant amount of information regarding the natural pathogenesis of OROV infections. It is known that within two to four days from the initial onset of systematic symptoms in humans, the presence of this virus is detected in the blood. In some cases this virus has also been recovered from the cerebrospinal fluid, but the route of invasion to the central nervous system (CNS) remains unclear. [9] In one study of three patients with oropouche meningoencephalitis confirmed by reverse transcription-polymerase chain reaction, two of the patients had underlying conditions that can affect the CNS and immune system (one had HIV/AIDS) and the third had neurocysticercosis; the authors thus theorized that CNS invasion by OROV can be facilitated by preexisting damage to the blood-brain barrier. [16]
To further elucidate the pathogenesis of OROV, experimental studies using murine models have been performed. [19]
BALB/c neonate mice were treated with this virus subcutaneously and presented clinical symptoms five days after inoculation. [9] The mice revealed a high concentration of the replicating virus in the brain along with inflammation of the meninges and apoptosis of neurons without encephalitis, [9] which is inflammation of the brain due to an infection. [9] These findings confirmed the neurotropism of this virus, which means that this virus is capable of infecting nerve cells. Immunohistochemistry was used to reveal how this virus had access to the central nervous system. [9] As the infection progresses, the virus crosses the blood-brain barrier and spreads to the brain parenchyma leading to severe manifestations of encephalitis. [9] OROV infection starts from the posterior parts of the brain and progresses toward the forebrain. [9] The oropouche virus spreads through the neural routes during early stages of the infection, reaching the spinal cord and traveling upward to the brain through brainstem with little inflammation. [9]
Laboratory diagnosis of the oropouche infection is done through classic and molecular virology techniques. [9] These include:
Clinical diagnosis of oropouche fever is challenging due to the nonspecific nature of the disease; in many cases, it can be confused with dengue fever or other arboviral illnesses. [13]
Oropouche fever occurs in outbreaks, so the chance contracting it even after being exposed to areas with midges or mosquitoes is small. [10] Prevention strategies include reducing the breeding of midges through source reduction (removal and modification of breeding sites) and reducing contact between midges and people. This can be accomplished by reducing the number of natural and artificial water-filled habitats in which the midge larvae grow. [10]
There is no cure or specific therapy for Oropouche fever; only symptomatic treatment (such as analgesics for pain relief and fluids to prevent and treat dehydration) is recommended. [20] [21] Aspirin is not a recommended choice of drug because it can reduce blood clotting and may aggravate the hemorrhagic effects and prolong recovery time.[ citation needed ] Ribavirin is ineffective and is not recommended. [6] [7]
The infection is usually self-limited and complications are rare. Illness usually lasts for about a week, although in extreme cases can be prolonged [3] and aches and fatigue can persist for several weeks. [8] Patients usually recover fully with no long-term ill-effects. There had been no recorded fatalities resulting from oropouche fever until 2024, when two deaths were confirmed in the Brazilian state of Bahia. [22] [23]
Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains—particularly in the back—and headaches. Symptoms typically improve within five days. In about 15% of people, within a day of improving the fever comes back, abdominal pain occurs, and liver damage begins causing yellow skin. If this occurs, the risk of bleeding and kidney problems is increased.
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.
Dengue fever is a mosquito-borne disease caused by dengue virus, prevalent in tropical and subtropical areas. It is frequently asymptomatic; if symptoms appear they typically begin 3 to 14 days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin itching and skin rash. Recovery generally takes two to seven days. In a small proportion of cases, the disease develops into severe dengue with bleeding, low levels of blood platelets, blood plasma leakage, and dangerously low blood pressure.
Chikungunya is an infection caused by the Chikungunya virus (CHIKV). The disease was first identified in 1952 in Tanzania and named based on the Kimakonde words for "to become contorted".
Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term arbovirus is a portmanteau word. Tibovirus is sometimes used to more specifically describe viruses transmitted by ticks, a superorder within the arthropods. Arboviruses can affect both animals and plants. 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.
Japanese encephalitis (JE) is an infection of the brain caused by the Japanese encephalitis virus (JEV). While most infections result in little or no symptoms, occasional inflammation of the brain occurs. In these cases, symptoms may include headache, vomiting, fever, confusion and seizures. This occurs about 5 to 15 days after infection.
Viral hemorrhagic fevers (VHFs) are a diverse group of animal and human illnesses. VHFs may be caused by five distinct families of RNA viruses: the families Filoviridae, Flaviviridae, Rhabdoviridae, and several member families of the Bunyavirales order such as Arenaviridae, and Hantaviridae. All types of VHF are characterized by fever and bleeding disorders and all can progress to high fever, shock and death in many cases. Some of the VHF agents cause relatively mild illnesses, such as the Scandinavian nephropathia epidemica, while others, such as Ebola virus, can cause severe, life-threatening disease.
Chandipura vesiculovirus (CHPV) is a member of the Rhabdoviridae family that is associated with an encephalitic illness, Chandipura encephalitis or Chandipura viral encephalitis, in humans. It was first identified in 1965 after isolation from the blood of two patients from Chandipura village in Maharashtra state, India and has been associated with a number of outbreaks of encephalitic illness in central India.
The o'nyong'nyong virus (ONNV) was first isolated by researchers at the Uganda Virus Research Institute in Entebbe, Uganda, during a large outbreak of a disease in 1959 that resembled dengue fever. ONNV is a togavirus, genus Alphavirus, is closely related to the chikungunya and Igbo Ora viruses, and is a member of the Semliki Forest antigenic complex. The name was given to the disease by the Acholi tribe during the 1959 outbreak. The name comes from the Nilotic language of Uganda and Sudan and means "weakening of the joints". The virus can infect humans and may cause disease.
Murray Valley encephalitis virus (MVEV) is a zoonotic flavivirus endemic to northern Australia and Papua New Guinea. It is the causal agent of Murray Valley encephalitis. In humans, it can cause permanent neurological disease or death. MVEV is related to Kunjin virus, which has a similar ecology, but a lower morbidity rate. Although the arbovirus is endemic to Northern Australia, it has occasionally spread to the southern states during times of heavy rainfall during the summer monsoon season via seasonal flooding of the Murray-Darling River system. These outbreaks can be "...decades apart, with no or very few cases identified in between".
Oropouche orthobunyavirus (OROV) is one of the most common orthobunyaviruses. When OROV infects humans, it causes a rapid fever illness called Oropouche fever. OROV was originally reported in Trinidad and Tobago in 1955 from the blood sample of a fever patient and from a pool of Coquillettidia venezuelensis mosquitoes. In 1960, OROV was isolated from a sloth and a pool of Ochlerotatus serratus mosquitoes in Brazil. The virus is considered a public health threat in tropical and subtropical areas of Central and South America, with over half a million infected people as of 2005. OROV is considered to be an arbovirus due to the method of transmission by the mosquitoes Aedes serratus and Culex quinquefasciatus among sloths, marsupials, primates, and birds.
Zika fever, also known as Zika virus disease or simply Zika, is an infectious disease caused by the Zika virus. Most cases have no symptoms, but when present they are usually mild and can resemble dengue fever. Symptoms may include fever, red eyes, joint pain, headache, and a maculopapular rash. Symptoms generally last less than seven days. It has not caused any reported deaths during the initial infection. Mother-to-child transmission during pregnancy can cause microcephaly and other brain malformations in some babies. Infections in adults have been linked to Guillain–Barré syndrome (GBS).
A reverse zoonosis, also known as a zooanthroponosis or anthroponosis, is a pathogen reservoired in humans that is capable of being transmitted to non-human animals.
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.
Zika virus is a member of the virus family Flaviviridae. It is spread by daytime-active Aedes mosquitoes, such as A. aegypti and A. albopictus. Its name comes from the Ziika Forest of Uganda, where the virus was first isolated in 1947. Zika virus shares a genus with the dengue, yellow fever, Japanese encephalitis, and West Nile viruses. Since the 1950s, it has been known to occur within a narrow equatorial belt from Africa to Asia. From 2007 to 2016, the virus spread eastward, across the Pacific Ocean to the Americas, leading to the 2015–2016 Zika virus epidemic.
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.
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.
In October 2013, there was an outbreak of Zika fever in French Polynesia, the first outbreak of several Zika outbreaks across Oceania. With 8,723 cases reported, it was the largest outbreak of Zika fever before the outbreak in the Americas that began in April 2015. An earlier outbreak occurred on Yap Island in the Federated States of Micronesia in 2007, but it is thought that the 2013–2014 outbreak involved an independent introduction of the Zika virus from Southeast Asia. Investigators suggested that the outbreaks of mosquito-borne diseases in the Pacific from 2012 to 2014 were "the early stages of a wave that will continue for several years", particularly because of their vulnerability to infectious diseases stemming from isolation and immunologically naive populations.
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.