It first appeared in the United States in New York in — most likely carried by an infected stowaway mosquito in a plane or cargo ship.
Within four years the virus had swept across the country with the seasonal movement of infected birds and arrived in the Los Angeles area in late Human cases occur in Los Angeles every year.
West Nile virus is now a permanent part of the ecology of local bird and mosquito populations and will never go away. Chikungunya virus is transmitted to people by two species of mosquitoes, Aedes aegypti and Aedes albopictus also known as invasive Aedes.
Both species are found in Los Angeles County. Dengue virus DENV is a mosquito-borne virus that can cause mild to severe acute febrile illness in humans. It is now endemic year round in most countries in the tropics and sub tropics.
Facebook Twitter LinkedIn Syndicate. Minus Related Pages. For Healthcare Providers. Mosquito Control. Activity and Surveillance. Outbreak areas are typically found along major bird migratory routes, with the largest outbreaks having occurred in Greece, Israel, Russia, Romania, and the United States.
Since there is no vaccine for humans, the only way to reduce the spread of this dangerous disease is to raise awareness of prevention measures through public education and to implement mosquito surveillance and control programs in at-risk areas.
West Nile virus is spread by the Culex species of mosquito. The main vector species in the U. These mosquitoes typically feed from evening to morning. It is a medium-sized mosquito with a brownish or grayish body and brown wings. Their larvae thrive in containers of stagnant, polluted water, and thus these mosquitoes are the primary target of the campaign to drain backyard sources of standing water as a way to reduce the incidence of WNV.
Louis encephalitis, Western Equine encephalitis, and heartworm in dogs. Culex tarsalis lives throughout the U. It is a black mosquito distinguished by a white band on its proboscis, as well as white stripes along its middle and hind legs. Culex tarsalis is most active in the few hours after sunset. Only about one person in five bitten by an infectious mosquito develops symptoms.
Furthermore, the chance of severe symptoms is lower in children than in older adults. If a mosquito bites my child, should he or she be tested for West Nile Virus? Only a very small percentage of mosquitoes carry the virus, and only one person in five bitten by infectious mosquitoes will develop symptoms.
It your child was bitten when West Nile virus is known to be active and you are concerned about symptoms that are developing, then consult a physician.
However, severe disease more likely in older adults may require hospitalization and treatment of symptoms. Is my child at risk for becoming infected with West Nile Virus while attending school?
Generally, the risk of infection is quite low. The key transmitters of West Nile virus Culex mosquitoes do not bite during the day. Also, in Colorado the summer school vacation months of July and August are when most infections are expected to occur.
Should children avoid outdoor field trips and playing outdoors because of West Nile virus? No, but precautions against mosquito bites should be taken if West Nile virus is known to be active in the area.
Wear shoes, socks, long pants and a long-sleeved shirt when outdoors for long periods of time, especially during the evenings, which is the period when Culex mosquitoes are most active. Use an effective mosquito repellent according to the directions on the label. What can I do around my home to help protect my children from exposure to mosquitoes?
Mosquitoes breed in standing water. The most effective means of reducing the number of mosquitoes around your home is to reduce or eliminate standing water.
If standing water, such as in a fish pond, is permanent then it can be treated with floating Bti briquets or similar larvicides. When virus levels in birds reach a certain level then mosquitoes can transmit the virus to other animals, especially horses. Symptoms include listlessness, stumbling, in coordination, weakness of the limbs, partial paralysis, and death. Usually there is not a fever.
Most evidence indicates that the virus does not build to high enough levels in horses to be acquired by mosquitoes. In other words, horses become ill from West Nile virus, but they do not become infectious. Can a horse infected with West Nile virus infect horses in neighboring stalls? West Nile virus is transmitted by infectious mosquitoes.
There is no evidence for horse-to-horse transmission of West Nile virus. Can you get infected with West Nile virus by caring for an infected horse?
There is no evidence for horse-to-person transmission of West Nile virus. Is there anything I can do to protect my horse against West Nile Virus?
The best way to protect your horse is to make sure that it has been properly vaccinated. The first time immunization takes two doses 3 to 6 weeks apart. The second dose should be completed before the peak season for mosquito activity July-August. An annual booster is required every year thereafter.
The vaccine is only available through a licensed veterinarian. Will these vaccines protect my horse against West Nile virus infection? There is a specific vaccine for West Nile virus that is necessary to protect your horse.
There is a specific vaccine for West Nile virus. Sick horses should be in the care of a veterinarian. Treatments address the symptoms displayed by the individual animal. There is no cure. Since sick horse do not become infectious mosquitoes can acquire the virus from the horse and since there is no evidence for horse to horse transmission, there is no reason to destroy infected animals. What signs of West Nile virus infection should I look for in domestic animals? Except for horses most domestic animals are not expected to have noticeable symptoms of West Nile virus infection.
A few infections have been reported from dogs, cats, squirrels and several other wild and domestic animal species. There is experimental evidence for infections in cats, cows, pigs, sheep, chickens and several other species. Can sick dogs or cats be carriers and transmit West Nile Virus to people and other dogs or cats? Can you get West Nile virus directly from birds, game or domestic animals? This virus is transmitted mostly by mosquitoes. There is no evidence for animal-to-person transmission of West Nile virus, although there is some evidence for crow-to-crow transmission.
The best way to protect them is to reduce the amount of mosquito activity in the area. The most effective means of doing this is to reduce or eliminate all standing water.
If standing water, such as in a fish pond or stock tank, is permanent then it can be treated with floating Bti briquets or similar larvicides. The use of insecticides to control adults also may be warranted in certain high risk situations. If possible, animals should be kept indoors at night.
Contact your veterinarian if you are concerned that your pet might have West Nile virus infection. Except for horses, most domestic animals have not shown symptoms of West Nile virus. There is no evidence that mosquitoes can acquire the virus from infected dogs or cats. Also, the chance for fatal cases in dogs and cats is thought to be extremely low.
During the first three years of West Nile virus in the United States most cases of infected birds involved American crows. However, the number of bird species affected by West Nile virus expanded greatly in There are now records of West Nile virus mortality in native bird species and 11 exotic species. The number of individual birds sickened or killed is unknown, although it is thought that crows and related species have been most affected.
The kinds of birds affected by West Nile virus expanded greatly in Many different kinds of birds were reported killed by West Nile virus in We are still learning which kinds of birds are susceptible and what their risks are from West Nile virus. Assume that your pet birds and poultry are at some risk and keep them indoors, if possible, during high risk periods. If your birds cant be kept indoors then take steps to reduce the amount of local mosquito activity.
The most effective means of reducing the number of mosquitoes around your home is to reduce or eliminate all standing water. Where in Colorado have birds infected with West Nile virus been reported? West Nile virus arrived in the state late in Most infected birds were found in river valleys in the eastern part of the state. It is likely that infected birds will be found over a much wider area in the future. If I see a lot of crows roosting in an area, should I be concerned about West Nile virus?
However, if you see several dead crows you should report the location to your local health department. How can I report a sighting of dead bird s for West Nile virus testing? Contact your local health department for information on reporting and collecting dead birds. A list of Colorado health departments is found at www. Why are crows, but not most other dead birds, tested for West Nile virus?
Crows are very susceptible to the virus, which builds to very high concentrations in their blood. A die-off of crows is a strong indicator of local West Nile virus activity.
Other kinds of birds may not be as susceptible and thus not as useful in detecting the presence of the virus. Why have some areas stopped collecting dead birds for West Nile virus testing? Birds are collected to test for the presence of West Nile virus. Once it is certain that the virus is established in an area there is little to be gained from additional testing, which is expensive. However some public health agencies may monitor reports of dead birds, particularly highly susceptible species such as crows.
This information can be useful in tracking seasonal activity of the virus. What information about the dead bird do I need to give my local health department for West Nile virus testing? Early in the season your health department may want information on how to get the bird from you for West Nile virus testing.
Later in the season they will just want the location. What should I do with the dead bird until it is picked up for testing for West Nile virus? Your local health department will give you instructions on how to handle the bird. It is most likely that they will ask you to store it in a non-food refrigerator or freezer. Use gloves to handle the carcass.
If a freezer is not available, you may be asked to cover the bird in ice and then cover the ice with a bucket. The bird may be picked up with a gloved hand or shovel, double bagged in plastic and placed in the trash.
This will change with the priorities of the health departments and the pattern of West Nile virus activity, so it is not possible to provide a specific answer for a given locality.
When will I receive the test results of the bird s that I submitted for testing for West Nile virus? The amount of time required for testing and reporting results is variable and depends on the current priorities of the health departments and the pattern of West Nile virus activity. Test results are used to monitor the activity of West Nile virus and to help decide whether it is necessary to implement mosquito control activities.
How can I help protect my family and myself from mosquitoes and the diseases, such as West Nile virus, they may carry?
If West Nile virus or other mosquito borne illnesses are known to be active in the area then precautions against mosquito bites should be taken. Wear shoes, socks, long pants and a long-sleeved shirt when outdoors for long periods of time, especially during the evenings. Also, take steps to reduce mosquito activity around the home.
What can I do to reduce my risk of becoming infected with West Nile virus? What else can we do to protect ourselves from mosquito bites and West Nile virus? Should we stay indoors to protect ourselves from mosquito bites and West Nile virus? The risk of contracting West Nile virus is low.
Yes, fogging will provide temporary relief from mosquitoes. However, new mosquitoes will quickly reinvade your backyard from nearby untreated areas, often later that same evening. The best way to control adult mosquitoes is through community or government sponsored programs that control adults over a wide area. Yes, the flooded area can be treated with floating Bti briquets or other approved larvicides.
A longer term solution would be to fill in the depression, if feasible, or improve the drainage in that spot. If your farm, particularly the irrigation system, has water that stands for more than a week then it is a potential mosquito breeding site. Maintain your irrigation system so that water moves freely.
Avoid leaks that allow ponding, and control vegetation that may impede water movement. Mosquito repellents are an effective means of personal protection against mosquito bites. Mosquito repellents lower the risk of contracting West Nile virus and other diseases transmitted by mosquitoes.
They allow you to continue to work and play outdoors even when mosquitoes are active. Use of a mosquito repellent is particularly important in areas where mosquitoes are active and management programs are not available or are not ongoing. The most important transmitters of West Nile virus are active at dusk and dawn. However, other kinds of mosquitoes, which also may be able to transmit the disease, bite during the day.
To be on the safe side, use a mosquito repellent whenever you plan on being outdoors for extended periods of time, but especially during the evening hours. To be on the safe side, use a mosquito repellent whenever you plan on being outdoors for extended periods of time, especially during the evening hours. Follow the instructions on the label. Mosquito repellent products differ in how long they last depending on the amount and type of active ingredient, as well as how it is formulated.
It is generally not necessary to use mosquito repellents indoors. If you are getting bitten indoors there are other steps to eliminate mosquito activity that should be taken first. The most important is to make sure all windows and doors are screened and that the screens are in good repair.
They work over fairly short distances so the mosquitoes remain in the area but do not land on your skin. Most studies have shown that the mosquito repellent called DEET is the most effective, and most public health agencies recommend the use of mosquito repellent products with this active ingredient. There are products with other active ingredients available, which generally have to be applied much more frequently than DEET products in order to be effective.
How does the percentage of DEET in a product relate to the amount of protection it gives? The percentage DEET affects the amount of time that a single application of the product will last. Lower percentage products give the same level of protection as more concentrated products, but do not last as long. DEET is the safest and most effective mosquito repellent known. It has been used billions of times over the last 50 years with only a few reports of adverse effects.
The risk of adverse effects from DEET use is substantially lower than the risk of contracting West Nile virus or other mosquito-borne illness while using a less effective mosquito repellent. Are non-DEET mosquito repellents effective e. Skin-So-Soft, plant-based repellents? Also, alternative products are made from ingredients that have not been tested so thoroughly for safety and effectiveness as DEET.
Until recently, repellent labels were required to use the approved chemical names of active ingredients, which for DEET is either N,N-diethyl-m-toluamide or N,N-diethlymethylbenamide. It has been used billions of times over the last 50 years with only a handful of reports of adverse effects.
What are some general considerations to remember in order to use mosquito repellent products containing DEET safely?
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