Mosquitoes and the West Nile Virus Still Affect the United States – and the World

13. How the Transmission Cycle Works Don’t think that the disease originates in mosquitoes; they’re only carriers. They receive the virus by biting infected birds. Sometimes,… Trista - August 28, 2019
West Nile virus Transmission Cycle. Image via SciELO

13. How the Transmission Cycle Works

Don’t think that the disease originates in mosquitoes; they’re only carriers. They receive the virus by biting infected birds. Sometimes, if a bird has high levels of the virus, the mosquito will transmit this to other birds, as well as other mammals, including humans. Thankfully, these mammals are not capable of producing high-enough levels of the virus for it to be passed on through other mosquitoes.

West Nile virus Transmission Cycle. Image via Shutterstock

More than 300 species of bird have at some point become infected with West Nile virus. The infection can kill species like the greater sage-grouse, American crow, and blue jay. Some North American birds, including the wood thrush, northern cardinal, and brown thrasher, have high levels of antibodies that can protect against West Nile virus.

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14. How West Nile Fever is Not Transmitted

Despite popular belief, you cannot transmit West Nile fever by coughing, sneezing, or touching another person. Nor can you contract the disease by touching live animals. You won’t get sick by handling dead birds either, though the act is not advised. When disposing of a dead bird, gloves should always be used, and the carcass should be placed in a plastic bag before being dumped in the garbage.

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Lastly, you cannot get West Nile Fever by eating infected birds or animals. Meat should be adequately prepared to spare yourself from salmonella or other bacteria, but you won’t contract the disease this way. Sharing bodily fluids will also not spread the West Nile virus infection.

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15. Vertical Transmission

A disease that is vertically transmitted is one that can be passed from a mother to her child during pregnancy or childbirth. This can happen when a woman is pregnant and gets an infection. A lot of the time, viruses and other diseases can be worse for a woman who is carrying a child.

Vertical Transmission | West Nile fever. Image via Freepik

West Nile fever is one of the diseases that can be vertically transmitted from a mother to her baby. Many studies of the West Nile virus note that this transmission is most often done in the winter because mosquitoes tend to infect in the fall. The rates of vertical transmission are lower in the fall and summer.

Credit: The BMJ

16. History of the West Nile Virus

In 1937, the West Nile virus was discovered in Uganda. In the summer of 1999, West Nile virus was reported for the first time in the United States. The discovery of this virus in New York City was the first time West Nile had been discovered outside the Eastern Hemisphere.

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West Nile virus has been diagnosed in North America, Africa, Europe, Australia, and Asia. Thousands of cases are reported in the United States alone each year. Most of the reported cases of West Nile virus occur in August and September, the most humid months. One of the best methods for early detection of a human outbreak is a bird surveillance system.

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17. Disease

Roughly 80 percent of those infected with West Nile virus do not report their condition because they present zero symptoms. Just 20 percent of people will show signs of being affected by the West Nile virus. Most symptoms start appearing between 3 and 14 days after being bitten by an infected mosquito.

Those with mild symptoms will recover entirely but may experience weakness and fatigue for several weeks or even months. Fever, meningitis, paralysis, and sometimes permanent brain damage can occur as a result of the West Nile fever. Those at risk of developing severe symptoms include people over the age of 60 and individuals who have medical conditions like diabetes or cancer.

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18. West Nile Fever

West Nile fever can be hard to diagnose because it presents symptoms that are incredibly similar to other viral infections. You may get a headache, but that can also indicate meningitis, encephalitis, and polio. Flu-like symptoms are common with West Nile fever.

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Within 3 to 6 days after symptoms begin to show, the West Nile Fever will take effect. You may feel sweaty, cold, weak, drowsy, and feverish. People with West Nile fever may also experience joint pain and gastrointestinal issues like nausea, loss of appetite, vomiting, and diarrhea. Nearly one-third of West Nile fever patients get a rash as well.

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19. Symptoms of West Nile Fever

What’s dangerous about this disease is that even people who are affected may not show any signs at all. So you may have been bitten but may never know whether you were infected with West Nile fever or not.

West Nile Fever Symptoms. Image via Verywell Health

In the few people who do show symptoms, the first thing they’ll notice is a fever. Other symptoms will start to present themselves, such as joint pains, body aches, a rash, diarrhea, vomiting, and headaches. Fatigue and weakness follow afterward, which it may take weeks or months for the infected person to recover from. It’s also possible to develop West Nile neuroinvasive disease, which attacks a person’s central nervous system, causing swelling in the brain and other neurological issues.

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20. More Severe Symptoms of West Nile Fever

In sporadic cases, severe symptoms may present themselves. About 1 in 150 people can exhibit these serious symptoms and include the central nervous system being affected, such as encephalitis or meningitis. Other symptoms include a very high fever, neck stiffness, coma, tremors, vision loss, numbness, paralysis, and convulsions. The elderly and those with certain medical conditions, such as kidney disease, diabetes, or hypertension are more prone to these serious symptoms.

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When the central nervous system is affected, it can make it difficult for the body to function. You may develop paralysis, brain swelling, muscular weakness, and absent reflexes. Luckily, less than 1 percent of people infected with West Nile fever will experience these issues.

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21. Diagnosing and Treatment of West Nile Fever

The only way to receive a diagnosis for West Nile fever is to go to your doctor if you experience any of the symptoms described above. A blood test will have to be done to see if your blood contains evidence of the virus.

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If you do receive a positive diagnosis, then there isn’t much you can do except manage the symptoms. There is no cure for West Nile fever, so that means you’ll have to treat the symptoms long-term. You can take over the counter pain relievers to reduce your day-to-day pain and your fever. For those suffering from severe symptoms, hospitalization is necessary to deal with them.

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22. Risk Factors for the West Nile Virus

Individuals with a suppressed immune system or a history with organ transplantation may be more susceptible to developing an infection with West Nile virus. Additionally, being over the age of 50, having hypertension and diabetes, and being male present risks of getting West Nile fever. There are also genetic factors involved.

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Some people have a mutation of the gene CCR5, which provides some protection from HIV. Unfortunately, this mutation can cause severe complications of the West Nile virus infection. Nearly 5 percent of West Nile disease patients have the CCR5 genetic mutation. Occupations that have a high risk of contracting West Nile virus include landscapers, loggers, farmers, painters, construction workers, and pavers.

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23. Diagnosis of the West Nile Virus

Indicators that a person should be tested for West Nile virus are based on symptoms and locations and dates of travel. Activities and the history of the infection in areas visited are also examined. If a person has recently been bitten by a mosquito and presents neurological illness symptoms, they should also be tested for West Nile virus.

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To test for West Nile virus, a patient’s blood or cerebrospinal fluid is screened. Indicators of West Nile virus in the blood will be an elevated level of protein, unusual lactic acid and glucose levels, and an absence of erythrocytes. Some companies offer testing kits specifically designed to diagnose West Nile virus.

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24. Prevention of the West Nile Virus

There are several steps to take in order to prevent contracting West Nile virus. These guidelines are used for all mosquito-borne illnesses. When traveling to an area that is at risk for West Nile virus, stay in a well-screened or air-conditioned room. Sleep in a bed that is surrounded by a protective mosquito net.

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In humid climates like Florida, most mosquitoes are active at dawn and dusk. Stay inside during those times to reduce your risk of being bitten. You can find insect repellents that contain DEET, which is excellent for repelling mosquitoes. Apply sunscreen and then spray on insect repellent to keep your skin safe from the sun and mosquitoes.

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25. Monitoring and Controlling the West Nile Virus

To find samples of West Nile virus, researchers will use specialized traps to capture mosquitoes. These types of traps include carbon-dioxide-baited traps, ovitraps, and gravid traps. They also will take blood samples from wild dogs, birds, and monkeys.

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The brains of dead birds are tested after they have been found by animal control agencies. Blood samples from wild birds and chickens are examined to identify specific antibodies of the West Nile virus. The best way to prevent West Nile virus from spreading is with mosquito control. Getting rid of abandoned swimming pools and spraying larvicide in active breeding areas are effective methods of control.

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26. The Prognosis for West Nile

West Nile virus is not a massive problem at the moment, but experts believe that it may become more severe than they have predicted. Recent outbreaks indicate that it could take between 60 and 90 days to recover from a mosquito infestation and West Nile virus outbreak.

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Those that experience a mild case of West Nile fever are just as likely as severe patients to experience tremors, motor skill dysfunctions, and other issues for more than a year after being infected. Recovering from West Nile virus involves a very long convalescent period and much fatigue. Those that have been infected with West Nile virus have a higher risk of developing kidney disease.

Credit: Los Angeles County Medical Association

27. Epidemiology

In 1937, the first instance of West Nile fever was found in Uganda. A woman at Omogo, located in the West Nile district, reported feeling feverish while researchers were investigating the yellow fever virus. In 1939, areas of the Congo, Sudan, and the White Nile region tested positive for West Nile virus.

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It was discovered in Egypt in 1942 and India in 1953. A 1950 survey in Egypt found that 90 percent of Egyptians over the age of 40 had West Nile virus antibodies. West Nile virus was noted in horses for the first time in France and Egypt in the 1960s. It was then that it was recognized in Australia, southern Europe, and southwest Asia.

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28. Weather Associated with the West Nile Virus

Experts have found that an area that experiences a severe drought will have a higher number of West Nile virus cases in the next year. The population of fish in a body of water will decrease during a drought, removing predators that feed on mosquito eggs. This occurrence will allow more mosquitoes to breed and lay eggs on water.

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Another risk for an uptick in West Nile virus is hotter weather. Areas where the climate has become warmer and more humid will see an increase in the mosquito population. Higher temperatures also provide a shorter replication time for the virus. Additionally, it will cause an increased viral load in mosquitoes and birds.

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29. Researching the West Nile Virus

Several vaccines have been developed for West Nile virus, but research is still ongoing. There is one that was designed for horses and is given to birds at some zoos across the globe. Scientists do not know the effectiveness of this vaccine yet. There is an antiretroviral drug used to treat HIV, which shows promise against encephalitis caused by West Nile virus.

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What experts do know is that the rate of transmission to cats and dogs is highly unlikely. They show virtually no signs of infection. There have not been any reported cases of dog to human or cat to human transmission.

Mosquito with insect repellent spray. Image via Freepik

30. Using Insect Repellent

Look for products that are EPA-rated; this means that they’ve proven to be effective and safe to use. Look for products that have picaridin, para-menthane-diol, oil of lemon eucalyptus, or 2-undecanone. It would be best if you exercise caution when using insect repellent around babies and young children, as they’re more sensitive to these kinds of chemicals. Do not use repellent on babies who are younger than two months old. To combat mosquitoes, dress them in long clothing that covers their arms and legs. Mosquito netting can also be used on strollers to keep them safe.

Mosquito netting. Image via Freepik

Repellents should also not be used anywhere on a child’s face or irritated skin. To be safe, spray repellent on your hands first and then apply it to the child’s face. If you’re experiencing a hot summer day, it’s a good idea to put your sunscreen on first and then apply your insect repellent. That way, you’re not causing the sunscreen to run off your body and minimize your protection against the sun.

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31. Wearing Long Sleeves

In addition to wearing repellent, you can also wear long sleeves and pants to help you prevent getting bitten. To strengthen your chances, try treating your clothing with permethrin. This is a chemical that is designed to repel mosquitoes if they get close to it.

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When applied to clothe, it provides protection even after multiple washes. Always follow the product instructions to ensure that you’re applying it correctly. Never use permethrin directly on your skin. Wearing long sleeves when you’re outdoors not only protects you from bug bites, it can also protect you from the sun’s harmful UV rays.

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32. Controlling Mosquitoes Inside and Outside

To keep the mosquitoes outside, use screening on your windows and doors so that you can still allow fresh air in without letting the bugs in as well. If possible, use air conditioning to help circulate air around your home instead.

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However, what about outside? If you want to spend some time in your yard, you need to kill the mosquitos before they become a problem. You can do this by eliminating any source of standing water. This is because mosquitoes lay their eggs in the water, which hatch into larvae. It would help if you emptied any buckets, tires, birdbaths, or flower pots that may have water inside them and leave them in the sun to dry completely.

Mosquitoes larvae. Image via Shutterstock

33. Utilizing a Larvicide

Although removing standing water will both get rid of mosquitoes that want to lay eggs as well as kill of the larvae, it may not be possible in some cases. When that happens, you can use a larvicide to kill off the larvae. This can come in the form of “mosquito dunks,” which are rings or tablets you can place in standing water to kill the larvae off.

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There are many different types of larvicide to choose from. Biological agents use natural bacteria to attack the larvae from inside their digestive tract. Chemical agents like methoprene are designed to stop the growth cycle of the larvae and prevent them from becoming adults. Occasionally, people use sound energy transmitted into the water. This technique instantly ruptures a larva’s bladder, leading to their death.

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34. Using Adulticides

These are more than just mosquito repellents; these are the means to kill adult mosquitoes outright. These chemicals will cut back on mosquito populations, making it more difficult for them to breed as well as reducing the chances that people can get sick. These can be found in local outdoor stores so that you can apply it around your home.

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The best place to spray an adulticide is under plants and on the undersides of tree and bush leaves. This is because mosquitoes like to rest under plants. You can also spray it on decks, porches, eaves, and in shady, moist areas. Inside your home, spray adulticides in your laundry room, behind furniture, in closets, and under sinks.

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35. Staying Safe While Overseas

Depending on where you’re going, you may be heading right into Mosquito City for your vacation spot. Do a little research before you get there to see where you’ll be spending the majority of your time. Choose a hotel that has screens on the windows and doors.

Screens on the windows and doors. Image via Shutterstock

If you can, bring mosquito netting with you to drape over your bed or over the windows to minimize your chances of being bitten. Don’t forget to pack bug spray! Having mosquito repellent on hand at all times will help you keep them from not only buzzing around and annoying you, but also from biting. You can also find special bracelets designed for repelling unwanted bugs.

West Nile virus | crows and jays. Image via The New York Times

36. Susceptible Bird Species

Because the virus originates with birds, several species are more prone to getting the West Nile virus than others. These include crows and jays, and you should always report the sighting of a dead bird to the local authorities. That way, a West Nile virus outbreak can be curtailed before it’s even started.

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Other bird species can contract the disease by eating infected prey birds. Once the disease has been contracted, the bird can become seriously ill and die as a result. If you see a dead bird on your property, don’t pick it up yourself. Call Animal Control so an expert can dispose of the animal. That way, you can prevent transmitting the West Nile virus to yourself and your pets.

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37. Staying on Top of the Situation

To ensure that these measures are working to keep mosquitoes at bay, professionals are always monitoring the effectiveness of them against adults and larvae alike. When evidence shows that something is no longer working, then solutions have to be drafted before the situation spirals out of control.

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This may involve using a newer, better insecticide to control the problem of finding some other way to kill mosquitoes more easily. Either way, mosquitoes have been a problem for many years that no one has found a permanent solution for. As the climate around the world begins to get warmer, the number of mosquitoes on the planet will continue to rise.

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38. Climate Change and West Nile Fever

The complex phenomenon known as climate change has been affecting human health in more ways than one. Many people may not want to face facts, but the effect climate change is having on planet Earth is serious and devastating. It has also had a massive impact on diseases like West Nile fever by changing its seasonality and distribution.

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Mosquitoes usually only infected people during the summer months. This is when people venture out due to warmer weather. However, since the months and weather patterns are no longer predictable, mosquitoes are becoming more and more active during the earlier months of the year.

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39. Climate Change Increases Numbers

Weather conditions, such as increased rainfall, warmer temperatures, and humidity, affect the survival and reproduction rates of mosquitoes, and they’ve been going up year after year. Larvae are also maturing a lot faster, making it easier for them to transmit the West Nile virus and other diseases to hosts once they’re mature.

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At this rate, it will become harder and harder to keep mosquito numbers low, meaning that the number of West Nile fever cases will likely go up. That’s why you must protect yourself from mosquitoes wherever you go outside. Also, be aware of the symptoms of West Nile fever so you can get treatment as soon as possible.

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40. Geographic Shifts

Another thing climate change has caused is the shifting of the mosquito populations. In areas where they’re usually high, such as Arizona and California, for example, some years have produced low numbers. Instead, these numbers are moving on to other under-prepared areas. They typically do not take such measures to protect themselves.

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Areas where the climate is usually cold year-round are experiencing warmer period due to climate change. For this reason, they may not have the idea to protect against mosquitoes before they start to overpopulate. Be aware if there are areas in your town that have standing water as well as a high number of dying birds.