West Nile Virus in the United States

Summer is the time for soaking up the sun and enjoying a cold drink. Kids are waiting for school to end and for a summer filled with outdoor fun to begin. Families nationwide are anxiously waiting for the day they can escape on their summer vacations.

Unfortunately, a hidden threat people often forget about also awaits summertime. This hidden threat is West Nile virus, and it’s most prevalent in the United States during the summer. Let’s dive into some basic information about West Nile virus, what you can do to avoid it, and how you can still enjoy a memorable summer outdoors.

What is West Nile Virus?

West Nile virus was first found in the United States in 1999 in a group of people in New York. Around the same time, an unusual number of birds were dying from a viral disease. Researchers believe that the West Nile virus may have been introduced to the United States from infected birds migrating from Israel. Over the years, more birds around the country became hosts to West Nile virus.

Birds don’t give West Nile virus to humans. For someone to get West Nile virus, they need to have a bite from a mosquito that fed on an infected bird. As the number of infected birds increased, the number of infected humans also increased.

Symptoms

In most cases of West Nile virus, the infected individual is asymptomatic. Being asymptomatic means the person has no symptoms of being sick. Some cases of West Nile virus cause flu-like symptoms that go away after some rest and use of over-the-counter medicine. Severe cases of West Nile virus have more serious neurological symptoms that indicate the virus has reached the central nervous system.

Symptomatic West Nile Virus Infection

Although most cases are asymptomatic, there is still the possibility of illness. Having symptoms doesn’t mean the virus has reached the nervous system.

Symptomatic West Nile virus can have symptoms that include:

• Rash on the trunk

• Fever

• Nausea and vomiting

• Muscle aches

• Headache

• Tiredness

As of September 2023, there have been 552 reported human cases of West Nile virus in the United States.

Neuro-invasive Virus Symptoms

Of the 552 reported cases in the United States, 379 of those cases reached the central nervous system. Healthcare professionals recommend that a person experiencing any new neurological symptoms seek medical attention.

Neurological symptoms include:

• Stiff neck

• Disorientation

• High fever

• Coma

• Tremors

• Paralysis

Keep in mind that the vast majority of West Nile virus cases are asymptomatic and unreported.

Diagnosis

How do you know if you have West Nile virus? If a doctor suspects West Nile virus, they may order a variety of tests.

The most common ways of diagnosing West Nile virus involve:

• Specific blood antibody tests

• Lumbar puncture for Cerebral Spinal Fluid (CSF) analysis

• Reviewing history of potential exposure to mosquitoes with West Nile virus

Diagnosis can be a challenge for healthcare providers because routine tests don’t detect West Nile Virus. The more invasive tests, like lumbar punctures, are done on people with symptoms.

Causes of Infection

West Nile virus is classified as a “vector-borne” illness. A vector is a living organism (usually mosquitos, fleas, or ticks) that gives an infection from animals to humans, or from human to human.

Areas in the United States that are most at risk for West Nile virus infections are the areas where mosquitoes like to breed. Mosquitos tend to lay their eggs in contaminated stagnant water, like in drainage ditches, birdbaths, buckets, planters, or trash bins. Regions experiencing hurricanes with destructive flood waters are especially at risk for increased mosquito egg-hatching.

Is West Nile Virus Contagious?

Unlike the flu or other viruses, West Nile virus isn’t spread through coughing or sneezing. In the rare instance that someone contracts West Nile virus, it’s probably from the bite of an infected mosquito. Getting West Nile virus from a blood transfusion, during pregnancy or birth, or from breast milk is extremely unusual. Anyone can stay informed on reported West Nile virus infections by visiting the Centers for Disease Control (CDC) website.

Prevention and Treatment

There are no vaccines or medications designed for treating West Nile Virus in humans. Treatment of West Nile Virus mainly involves the management of symptoms, and letting the virus run its course.

Avoid Mosquito-Infested Areas

Avoidance of mosquito-infected areas during peak “biting times” is another way of preventing the spread of West Nile virus. Mosquitos are the most active in summer and fall when they’re actively breeding.

How to Protect Yourself if Avoidance isn’t an Option

Communities exposed to mosquitos, and people who spend a lot of time outdoors during the summer can take other measures to avoid infection.

• Wearing long-sleeves

• Insect repellant spray

• Light-colored clothing (to absorb less heat, which mosquitos are attracted to)

• Less time outside from dusk until dawn (when mosquitos are most active)

Other information on mosquito control can be found on the CDC website.

Hospital Treatment

Although there are no vaccines or treatments for West Nile virus in humans, and most cases are asymptomatic, it is still possible for people to experience uncomfortable symptoms. These symptoms can sometimes require hospitalization and closer observation.

Severe Cases

In the unlikely scenario where someone has a serious West Nile virus infection, there is potential for a devastating outcome.

People with severe cases can be hospitalized for the following treatments:

• Intravenous fluids

• Pain management

• Rest

• Nursing care and observation

• Respiratory support

Older adults and immunocompromised people are most at risk for symptomatic and serious cases of West Nile virus infections. The incidence of severe infection in children and young adults is low, but not unheard of.

Summary

As scary as West Nile virus sounds, it is fairly preventable. Most people are asymptomatic, but symptoms to watch out for are neck stiffness, confusion, high fevers, and tremors. Even though mosquitos pick up the virus from infected birds, mosquitos are what give the virus to humans. Staying on top of mosquito control measures and mosquito bite prevention can help limit the spread of West Nile virus.

Whether you use bug spray during the hot, humid summers, limit time outdoors at dusk, or wear long sleeves and long pants, you can avoid your chances of getting bitten. The virus has gained more attention over the years due to its potential impact on public health. Understanding the illness, including its transmission, symptoms, and prevention can help you stay protected and allow you to have a relaxing summer.

References

Centers for Disease Control and Prevention. (2022, May 5) Mosquito control.

Centers for ‘ Disease Control and Prevention. https://www.cdc.gov/mosquitoes/mosquito-control/index.html

Centers for Disease Control and Prevention. (2023, June 13). West Nile virus.

Centers for Disease Control and Prevention. https://www.cdc.gov/westnile/index.html

Hadfield, J., Brito, A. F., Swetnam, D. M., F. Vogels, C. B., Tokarz, R. E., Andersen, K. G., Smith, R. C., Bedford, T., & Grubaugh, N. D. (2019). Twenty years of West Nile virus spread and evolution in the Americas visualized by Nextstrain. PLoS Pathogens, 15(10). https://doi.org/10.1371/journal.ppat.1008042

Kramer, L. D., Ciota, A. T., & Kilpatrick, A. M. (2019). Introduction, Spread, and Establishment of West Nile Virus in the Americas. Journal of Medical Entomology, 56(6), 1448-1455. https://doi.org/10.1093/jme/tjz151

McDonald, E., Mathis, S., Martin, S. W., Staples, J. E., Fischer, M., & Lindsey, N. P. (2021). Surveillance for West Nile Virus Disease — United States, 2009–2018. MMWR Surveillance Summaries, 70(1), 1-15. https://doi.org/10.15585/mmwr.ss7001a1

Petersen, L. R. (2019). Epidemiology of West Nile Virus in the United States: Implications for Arbovirology and Public Health. Journal of Medical Entomology, 56(6), 1456-1462. https://doi.org/10.1093/jme/tjz085

World Health Organization. (2017, October 3). West Nile virus. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/west-nile-virus