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West Nile virus. West Nile is a virus most commonly spread to people by mosquito bites. In North America, cases of West Nile virus (WNV) occur during mosquito season, which starts in the summer and continues through fall. WNV cases have been reported in all of the continental United States. There are no vaccines to prevent or medications...
What is West Nile virus?
Alaska, Hawaii, and Guam have no reported cases of West Nile virus in humans or animals. Distribution maps are available from the Centers for Disease Control. Are birds the only species that is susceptible to West Nile Virus infection?
Which US states have no reported cases of West Nile virus?
West Nile virus. Overview. A mosquito-transmitted virus causes most cases of West Nile infection. Most people infected with West Nile virus either don't develop signs or symptoms or have only minor ones, such as fever and mild headache. However, some people develop a life-threatening illness that includes inflammation of the spinal cord or brain.
What are the symptoms of West Nile?
The incubation period — the period between when you're bitten by an infected mosquito and the appearance of signs and symptoms of the illness — ranges from two to 14 days. West Nile virus has occurred in Africa, Asia, Europe and the Middle East. It appeared in the United States in the summer of 1999,...
What is the incubation period for West Nile virus?
What is the most common mosquito-borne disease in the United States?
Do people with WNV feel sick?
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What are 3 signs of West Nile virus?
These are the most common symptoms of West Nile fever:Fever.Headache.Body aches.Skin rash on trunk of body.Swollen lymph glands.
Where is West Nile virus most common in the US?
In the United States, West Nile virus has a marked seasonality with most cases occurring between July and October, with the highest rate of disease occurring in the Great Plains states (North and South Dakota, Wyoming, and Colorado).
How likely is it to get West Nile virus?
Even in areas where the virus is circulating, very few mosquitoes are infected with the virus. Even if the mosquito is infected, less than 1% of people who get bitten and become infected will get severely ill. The chances you will become severely ill from any one mosquito bite are extremely small.
How long after a mosquito bite do you get West Nile?
Most West Nile virus infections happen during warm weather, when mosquitoes are active. The incubation period — the period between when you're bitten by an infected mosquito and the appearance of signs and symptoms of the illness — generally ranges from four to 10 days.
Is West Nile virus curable?
There is no specific treatment for West Nile virus (WNV) disease; clinical management is supportive. Patients with severe meningeal symptoms often require pain control for headaches and antiemetic therapy and rehydration for associated nausea and vomiting.
Can you recover from West Nile virus?
About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with febrile illness due to West Nile virus recover completely, but fatigue and weakness can last for weeks or months.
What kills West Nile virus?
There is no treatment for the virus other than supportive care, and there is no vaccine to prevent it. Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms.
Who is most at risk for West Nile virus?
Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.
What part of the body does West Nile virus affect?
In one out of 150 cases, West Nile virus is a more serious problem. It can cause a dangerous infection that affects the brain and nervous system. This infection can cause lasting or permanent side effects, such as muscle weakness. Some people die.
Is there a test for West Nile virus?
WNV Antibody Testing Laboratory diagnosis is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect WNV-specific IgM antibodies. Immunoassays for WNV-specific IgM are available commercially and through state public health laboratories.
How fast does West Nile symptoms appear?
Usually, symptoms occur from 3 to 14 days after being bitten by an infected mosquito. There is no specific treatment for viral infections, other than to treat the symptoms and provide supportive care.
What percent of mosquitoes carry West Nile virus?
Louis encephalitis, though treatment can reduce the severity of the symptoms. The chance of getting sick from the WNV is very small. In areas where mosquitoes carry the virus, only about one out of 500 mosquitoes are infected.
How common is the West Nile virus in America?
CasesCasesMortality Rate of reported cases20162,1495%20172,0977%20182,6476%2019*9586%18 more rows
How many states have West Nile virus?
Of the 50 states, 42 have reported human cases. To date, 4,416 cases and 84 deaths have been reported to the Centers for Disease Control and Prevention of the United States (CDC), with 38 states reporting human cases. Colorado continues to be the most affected state (with 1,542 cases and 27 deaths...
Can you get West Nile virus in the USA?
West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States. It is most commonly spread to people by the bite of an infected mosquito. Cases of WNV occur during mosquito season, which starts in the summer and continues through fall.
How many cases of West Nile virus are in the US?
As of January 11, 2022, a total of 2695 cases of West Nile virus disease in people have been reported to CDC. Of these, 1855 (69%) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 840 (31%) were classified as non-neuroinvasive disease.
West Nile Virus Activity for 2022 - NYC Health - New York City
West Nile Virus Activity for 2022. West Nile Virus has been detected in the following areas:
Weekly updates: 2022 West Nile virus transmission season
Epidemiological summary. Since last week’s update, and as of 26 October 2022, European Union (EU) and European Economic Area (EEA) countries reported 5 human cases of West Nile virus (WNV) infection and no deaths related to WNV infections.
List of West Nile Virus Medications - Drugs.com
Drugs.com provides accurate and independent information on more than 24,000 prescription drugs, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. Data sources include IBM Watson Micromedex (updated 12 Oct 2022), Cerner Multum™ (updated 25 Oct 2022), ASHP (updated 12 Oct 2022 ...
West Nile Virus Disease Cases by State 2021 - CDC
*Includes confirmed and probable cases. †Includes cases reported as meningitis, encephalitis, or acute flaccid paralysis. ‡Presumptive viremic blood donors (PVDs) are people who had no symptoms at the time of donating blood through a blood collection agency, but whose blood tested positive when screened for the presence of West Nile virus.
West Nile Virus Activity by State 2021 | West Nile Virus | CDC
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Where is the West Nile virus found?
West Nile Virus (WNV) can cause neurological disease and death in people. WNV is commonly found in Africa, Europe, the Middle East, North America and West Asia. WNV is maintained in nature in a cycle involving transmission between birds and mosquitoes. Humans, horses and other mammals can be infected. West Nile Virus (WNV) is a member of the ...
How do mosquitoes get infected?
Mosquitoes become infected when they feed on infected birds, which circulate the virus in their blood for a few days. The virus eventually gets into the mosquito's salivary glands.
How is the West Nile virus transmitted?
West Nile virus is mainly transmitted to people through the bites of infected mosquitoes.
What are the symptoms of West Nile fever?
Symptoms include fever, headache, tiredness, and body aches, nausea, vomiting, occasionally with a skin rash (on the trunk of the body) and swollen lymph glands. The symptoms of severe disease (also called neuroinvasive disease, such as West Nile encephalitis ...
How to detect West Nile virus?
West Nile virus can be diagnosed by a number of different tests: 1 IgG antibody sero-conversion (or significant increase in antibody titers) in two serial specimen collected at a one week interval by enzyme-linked immunosorbent assay (ELISA); 2 IgM antibody capture enzyme-linked immunosorbent assay (ELISA); 3 neutralisation assays; 4 viral detection by reverse transcription polymerase chain reaction (RT-PCR) assay, and 5 virus isolation by cell culture.
How to prevent human WNV?
Effective prevention of human WNV infections depends on the development of comprehensive, integrated mosquito surveillance and control programmes in areas where the virus occurs. Studies should identify local mosquito species that play a role in WNV transmission, including those that might serve as a “bridge” from birds to human beings. Emphasis should be on integrated control measures including source reduction (with community participation), water management, chemicals, and biological control methods.
What is the main vector of WNV?
WN virus is maintained in nature in a mosquito-bird-mosquito transmission cycle. Mosquitoes of the genus Culex are generally considered the principal vectors of WNV, in particular Cx. Pipiens. WNV is maintained in mosquito populations through vertical transmission (adults to eggs).
How many nucleotides are in the WNV genome?
WNV is a positive-sense, single-stranded RNA virus. Its genome is approximately 11,000 nucleotides long and is flanked by 5′ and 3′ non-coding stem loop structures. The coding region of the genome codes for three structural proteins and seven nonstructural (NS) proteins, proteins that are not incorporated into the structure of new viruses. The WNV genome is first translated into a polyprotein and later cleaved by virus and host proteases into separate proteins (i.e. NS1, C, E).
How does West Nile fever spread?
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%.
What is the outer protein shell of a virus?
The outer protein shell is covered by a host-derived lipid membrane, the viral envelope. The flavivirus lipid membrane has been found to contain cholesterol and phosphatidylserine, but other elements of the membrane have yet to be identified. The lipid membrane has many roles in viral infection, including acting as signaling molecules and enhancing entry into the cell. Cholesterol, in particular, plays an integral part in WNV entering a host cell. The two viral envelope proteins, E and M, are inserted into the membrane.
What is the NS2B/NS3 protease?
Ribbon representation of the NS2B/NS3 protease of West Nile 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.
What is the structure of the WNV?
Electron microscope studies reveal a 45–50 nm virion covered with a relatively smooth protein shell ; this structure is similar to the dengue fever virus, another Flavivirus. The protein shell is made of two structural proteins: the glycoprotein E and the small membrane protein M. Protein E has numerous functions including receptor binding, viral attachment, and entry into the cell through membrane fusion.
What is the primary host of WNV?
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.
How does NS5 replicate?
In order to replicate its genome, NS5, a RNA polymerase, forms a replication complex with other nonstructural proteins to produce an intermediary negative-sense single-stranded RNA; the negative-sense strand serves as a template for synthesis of the final positive-sense RNA. Once the positive-sense RNA has been synthesized, the capsid protein, C, encloses the RNA strands into immature virions. The rest of the virus is assembled along the endoplasmic reticulum and through the Golgi apparatus, and results in non-infectious immature virions. The E protein is then glycosylated and prM is cleaved by furin, a host cell protease, into the M protein, thereby producing an infectious mature virion. The mature viruses are then secreted out of the cell.
How to prevent West Nile virus?
The best way to prevent West Nile Virus is to minimize the number of mosquitoes since that is how the virus moves from bird host to human. As a general rule, the easiest way to deal with mosquito pests is to prevent them from breeding around us in the first place, and this is quite easy here in the valley.
What is the West Nile virus?
West Nile Virus is a mosquito-borne virus contracted through mosquito bites. Only about 60% of people who have tested positive for the virus ever knew they were being bitten by mosquitoes, so it’s advisable to just assume they are about between dusk and dawn.
Why are mosquitoes bad for you?
Mosquitoes in urban settings can cause numerous health problems due to their ability to transfer, or vector, viruses and other disease-causing pathogens. At the beginning of July this year, 56 Arizonans had been confirmed to have West Nile virus, and all of the cases have thus far been located in the Phoenix valley. With human cases expected to soar this summer, our best defense is knowledge of the virus and mosquito management.
How to catch mosquitoes in your house?
Check for wriggling larvae in the toilet cisterns that are not flushed daily. Maintain water in drain traps. Use sticky tape over floor drains, sink over flows, etc. to see if you can catch mosquitoes emerging from areas you cannot see. Fogging for adults is a method sometimes employed by the city or county.
How long does it take for a mosquito to feed on a bird?
After a mosquito feeds on the blood of a bird infected with West Nile Virus, the virus goes through a short growth period before it is capable of being retransmitted – as few as four days for some mosquito species in Arizona. The infected mosquito, full of virus and ready to feed again, will look for a bird, human, or other animal for its next blood meal.
How to stop mosquito bites from itching?
Several strategies exist for relieving the itch of mosquito bites. The first step is the clean the bite area with soap and water. Topical corticosteroids can reduce the rash, itching, and discomfort. Topical diphenhydramine and caine-containing derivatives should be avoided because of concerns about inducing allergic contact sensitivity.
Why do mosquitoes need wet conditions?
Mosquitoes need wet conditions to lay their eggs and grow from an aquatic larva into a flying adult. HUMANS create the vast majority of the wet conditions used by mosquitoes in the Phoenix valley, and it is likely that many of us have mosquitoes developing in our neighborhoods and own backyards. We cannot eradicate every individual, but there are some very simple steps each of us can take to keep numbers low.
What causes West Nile virus?
West Nile virus is spread to humans through the bite of an infected female mosquito. The mosquitoes get the virus when they bite an infected bird. Crows and jays are the most common birds linked to the virus. But at least 110 other bird species also have the virus.
How is West Nile virus diagnosed?
Your doctor will order a blood test to check for antibodies to the West Nile virus. He or she may also do a lumbar puncture to test cerebrospinal fluid for signs of infection.
Can West Nile virus be prevented?
At this time, there's no vaccine available to prevent West Nile virus. The CDC recommends taking these steps to avoid mosquito bites and West Nile virus:
When should I call my healthcare provider?
Most people infected with the West Nile virus will have only mild symptoms. However, if any of the following serious symptoms develop, seek medical attention right away:
What diseases can be caused by the virus?
But, the virus can cause life-threatening illnesses, such as: Encephalitis (inflammation of the brain) Meningitis (inflammation of the lining of the brain and spinal cord) Meningoencephalitis (inflammation of the brain and its surrounding membrane)
What repels mosquitoes?
Mosquitoes are drawn to people’s skin odors and the carbon dioxide you breathe out. Many repellents contain a chemical, N, N-diethyl-m-toluamide (DEET), which repels the mosquito. Repellents are effective only at short distances from the treated surface, so mosquitoes may still be flying nearby. Always follow the directions on the insect repellent to determine how often you need to reapply repellent. To boost your protection from insect repellent, remember:
How old do you have to be to use DEET repellent?
(Some experts suggest that it's acceptable to apply repellent with low concentrations of DEET to infants older than age 2 months. For children younger than age 2, only one application per day of repellent containing DEET is recommended.)
How long does it take for a mosquito to get infected with West Nile?
The incubation period — the period between when you're bitten by an infected mosquito and the appearance of signs and symptoms of the illness — generally ranges from four to 10 days. West Nile virus has appeared in Africa, Asia, Europe and the Middle East.
How to protect yourself from West Nile virus?
You can lower your risk by protecting yourself from mosquitoes by using mosquito repellent and wearing clothing that covers your skin.
What happens when a mosquito bites a bird?
When a mosquito bites an infected bird, the virus enters the mosquito's bloodstream and eventually moves into its salivary glands. When an infected mosquito bites an animal or a human (host), the virus is passed into the host's bloodstream, where it may cause serious illness. West Nile virus generally spreads to humans and animals from bites ...
What is the West Nile virus?
A mosquito-transmitted virus causes most cases of West Nile infection. Most people infected with West Nile virus either don't develop signs or symptoms or have only minor ones, such as a fever and mild headache. However, some people develop a life-threatening illness that includes inflammation of the spinal cord or brain.
How to prevent West Nile virus?
Your best bet for preventing West Nile virus and other mosquito-borne illnesses is to avoid exposure to mosquitoes and remove standing water, where mosquitoes breed.
How does West Nile spread?
In a few cases, West Nile virus might have spread through other routes, including organ transplants and blood transfusions. However, blood donors are screened for the virus, greatly reducing the risk of infection from blood transfusions.
What are the symptoms of neurological infections?
Signs and symptoms of neurological infections include: High fever. Severe headache. Stiff neck. Disorientation or confusion. Coma. Tremors or muscle jerking.
What is the only species that is susceptible to West Nile virus?
Are birds the only species that is susceptible to West Nile Virus infection? West Nile Virus (WNV) has been detected in at least 48 species of mosquitoes, over 320 species of birds , at least 2 species of reptiles, and more than 25 mammalian species, including horses and humans. Birds are the natural host and reservoir of WNV.
What is the avian influenza?
Avian influenza (AI) is caused by an influenza type A virus that can infect poultry such as chickens, turkeys, pheasants, quail, domestic ducks, geese, and guinea fowl . It is carried by wild waterfowl (ducks and geese) and shorebirds. Learn more: USGS Avian Influenza.
What causes chronic wasting disease?
Chronic wasting disease is caused by a misfolded protein called a prion. All mammals produce normal prions that are used by cells, then degraded and eliminated, or recycled, within the body. When disease-associated prions contact normal prions, they cause them to refold into their own abnormal shape.
What is Goarn in the world?
Disease emergence and resurgence—the wildlife-human connection. In 2000, the Global Outbreak Alert and Response Network (GOARN) was organized as a global disease watchdog group to coordinate disease outbreak information and health crisis response. The World Health Organization (WHO) is the headquarters for this network.
What is white nose syndrome?
White-nose syndrome is an emergent disease of hibernating bats that has spread from the northeastern to the central United States at an alarming rate. Since the winter of 2007-2008, millions of insect-eating bats in at least 37 states and seven Canadian provinces have died from this devastating disease. The disease is named for the white fungus,...
How do you know if you have an infection in a wild animal?
Commonly reported signs in animals include weakness, stumbling, trembling, head tremors, inability to fly/walk, and a lack of awareness that allows them to be easily approached and handled.
Where in the US has West Nile been detected?
Where in the United States has West Nile Virus been detected in wildlife? West Nile Virus has been detected in all conterminous states of the U.S., the District of Columbia, and Puerto Rico. Alaska, Hawaii, and Guam have no reported cases of West Nile virus in humans or animals. Distribution maps are available from the Centers for Disease Control.
What is interferon therapy?
Interferon therapy is aimed at using substances produced by your immune system to treat encephalitis in people infected by West Nile virus. The research isn’t conclusive about the use of these therapies for encephalitis, but studies are promising.
How do mosquitoes transmit the West Nile virus?
Mosquitoes transmit this virus by biting an infected bird and then biting a person. Not all people with infected mosquito bites get the disease, however. WNV can be severe for people older than 60 years and people with weakened immune systems. If diagnosed and treated quickly, the outlook for West Nile virus recovery is good.
What causes West Nile virus?
Causes. Infected mosquitoes usually spread the West Nile virus. The mosquito first bites an infected bird and then bites a human or another animal. In rare cases, blood transfusions, organ transplants, breastfeeding, or pregnancy can transfer the virus and spread the illness.
How long does a West Nile virus last?
A severe infection can last for several weeks . In rare cases, a severe infection can cause permanent brain damage. A mild infection doesn’t usually last as long. Mild forms of West Nile virus may be confused with the flu. Symptoms include:
How long does it take to get a West Nile virus?
Symptoms. If you have West Nile virus, you will typically show the first virus symptoms within three to 14 days of being bitten. West Nile virus symptoms vary in severity. Severe symptoms can include: A severe infection can last for several weeks. In rare cases, a severe infection can cause permanent brain damage.
What to do if your brain is swollen?
If you experience brain swelling or other severe symptoms, your doctor may give you intravenous fluids and medications to lower the risk of infections. Research is currently being done on interferon therapy for West Nile virus. Interferon therapy is aimed at using substances produced by your immune system to treat encephalitis in people infected by ...
How long does fatigue last after West Nile?
Some symptoms, such as fatigue, can continue for up to several months after the initial infection. of people who get West Nile virus infections develop severe symptoms or neurological conditions such as meningitis or encephalitis. Of these cases, fewer than 10 percent. are fatal.
How many people get sick from West Nile?
Few ever get sick from West Nile virus. Only one in five people who contract West Nile virus have any symptoms. Most people who do have symptoms experience minor aches and pains that mirror influenza (the flu). In less than 1% of cases, West Nile virus causes a sometimes life-threatening infection that can make people very sick.
How do mosquitoes get West Nile?
Mosquitoes usually contract West Nile virus by biting an infected bird. When an infected mosquito bites you (or an animal), they transmit the virus through their saliva. In a very few cases, West Nile virus has spread: From mother to baby during pregnancy or breastfeeding. In a blood transfusion.
What does it mean when you have a rash on your stomach?
Itchy rash on your stomach or back. Swollen lymph nodes (such as the glands in your neck). Less than 1% of people who get West Nile virus experience more severe symptoms that affect the central nervous system. West Nile virus can cause encephalitis or meningitis (dangerous inflammation in the brain or spinal cord).
What is the West Nile virus?
What is West Nile virus? West Nile virus is an infectious disease caused by microscopic germs (called a virus) that can make you sick. Mosquitoes infected with the West Nile virus can give it to people or animals, such as horses, when they bite the skin. In most people, West Nile virus causes minor or no symptoms.
What test can confirm West Nile?
A simple blood test can confirm a West Nile virus diagnosis. This test looks for West Nile virus antibodies (proteins that show your body is fighting the virus) in your blood. If your symptoms are severe, your healthcare provider may recommend a spinal tap.
Why do some people have a lowered immune system?
Some people have a lowered immune system due to an autoimmune disease or medical conditions such as cancer. In rare cases, West Nile virus has spread through a blood transfusion or organ transplant. Hospitals now screen blood and organ donors for West Nile virus to minimize this risk.
What is the fever of West Nile?
It’s important to call your doctor if you have any severe symptoms of West Nile virus, such as: Intense, very painful headache. High fever (above 103° F or 39.5° C).
What is the most common mosquito-borne disease in the United States?
West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States. It is most commonly spread to people by the bite of an infected mosquito. Cases of WNV occur during mosquito season, which starts in the summer and continues through fall. There are no vaccines to prevent or medications to treat WNV in people.
Do people with WNV feel sick?
Fortunately, most people infected with WNV do not feel sick. About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness.
Outbreaks
Transmission
- Human infection is most often the result of bites from infected mosquitoes. Mosquitoes become infected when they feed on infected birds, which circulate the virus in their blood for a few days. The virus eventually gets into the mosquito's salivary glands. During later blood meals (when mosquitoes bite), the virus may be injected into humans and animals, where it can multiply and …
Signs and Symptoms
- Infection with WNV is either asymptomatic (no symptoms) in around 80% of infected people, or can lead to West Nile fever or severe West Nile disease. About 20% of people who become infected with WNV will develop West Nile fever. Symptoms include fever, headache, tiredness, and body aches, nausea, vomiting, occasionally with a skin rash (on the trunk of the body) and swoll…
Diagnosis
- West Nile virus can be diagnosed by a number of different tests: 1. IgG antibody sero-conversion (or significant increase in antibody titers) in two serial specimen collected at a one week interval by enzyme-linked immunosorbent assay (ELISA); 2. IgM antibody capture enzyme-linked immunosorbent assay (ELISA); 3. neutralisation assays; 4. viral detection by reverse transcriptio…
Treatment and Vaccine
- Treatment is supportive for patients with neuro-invasive West Nile virus, often involving hospitalization, intravenous fluids, respiratory support, and prevention of secondary infections. No vaccine is available for humans.
Vector and Animal Hosts
- WN virus is maintained in nature in a mosquito-bird-mosquito transmission cycle. Mosquitoes of the genus Culex are generally considered the principal vectors of WNV, in particular Cx. Pipiens. WNV is maintained in mosquito populations through vertical transmission (adults to eggs). Birds are the reservoir hosts of WNV. In Europe, Africa, Middle East and Asia, mortality in birds associ…
Prevention
- Preventing transmission in horses
Since WNV outbreaks in animals precede human cases, the establishment of an active animal health surveillance system to detect new cases in birds and horses is essential in providing early warning for veterinary and human public health authorities. In the Americas, it is important to hel… - Reducing the risk of infection in people
In the absence of a vaccine, the only way to reduce infection in people is by raising awareness of the risk factors and educating people about the measures they can take to reduce exposure to the virus. Public health educational messages should focus on the following: 1. Reducing the risk of …
Who Response
- The WHO regional office for Europe and WHO region of the Americas are intensively supporting WNV surveillance and outbreak response activities respectively in Europe and in North America, Latin America and the Caribbean, together with country offices and international partners.
Overview
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. …
Structure
Like most other flaviviruses, WNV is an enveloped virus with icosahedral symmetry. Electron microscope studies reveal a 45–50 nm virion covered with a relatively smooth protein shell; this structure is similar to the dengue fever virus, another Flavivirus. The protein shell is made of two structural proteins: the glycoprotein E and the small membrane protein M. Protein E has numerous functions including receptor binding, viral attachment, and entry into the cell through membrane f…
Life cycle
Once WNV has successfully entered the bloodstream of a host animal, the envelope protein, E, binds to attachment factors called glycosaminoglycans on the host cell. These attachment factors aid entry into the cell, however, binding to primary receptors is also necessary. Primary receptors include DC-SIGN, DC-SIGN-R, and the integrin αvβ3. By binding to these primary receptors, WNV enters the cell through clathrin-mediated endocytosis. As a result of endocytosis, WNV enters th…
Phylogeny
WNV is one of the Japanese encephalitis antigenic serocomplex of viruses, together with Japanese encephalitis virus, Murray Valley encephalitis virus, Saint Louis encephalitis virus and some other flaviviruses. Studies of phylogenetic lineages have determined that WNV emerged as a distinct virus around 1000 years ago. This initial virus developed into two distinct lineages. Lineage 1 and its multiple profiles is the source of the epidemic transmission in Africa and throughout the worl…
Host range and transmission
The natural hosts for WNV are birds and mosquitoes. Over 300 different species of bird have been shown to be infected with the virus. Some birds, including the American crow (Corvus brachyrhynchos), blue jay (Cyanocitta cristata) and greater sage-grouse (Centrocercus urophasianus), are killed by the infection, but others survive. The American robin (Turdus migratorius) and house sparrow (Pa…
Disease
Severe disease may also occur in horses. Several vaccines for these animals are now available. Before the availability of veterinary vaccines, around 40% of horses infected in North America died.
Epidemiology
According to the Center for Disease Control, infection with West Nile Virus is seasonal in temperate zones. Climates that are temperate, such as those in the United States and Europe, see peak season from July to October. Peak season changes depending on geographic region and warmer and humid climates can see longer peak seasons. All ages are equally likely to be infected but there is a higher amount of death and neuroinvasive West Nile Virus in people 60–89 years o…
Prevention
Prevention efforts against WNV mainly focus on preventing human contact with and being bitten by infected mosquitoes. This is twofold, first by personal protective actions and second by mosquito-control actions. When a person is in an area that has WNV, it is important to avoid outdoor activity, and if they go outside they should use a mosquito repellent with DEET. A person can also wear clothing that covers more skin, such as long sleeves and pants. Mosquito control …