What is West Nile Encephalitis?

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  • Written By: Lori Smith
  • Edited By: Michelle Arevalo
  • Last Modified Date: 23 December 2018
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West Nile encephalitis is a virus that causes inflammation of the brain, and other symptoms ranging in severity from mild infection to severe, life-threatening illness. A person usually becomes infected with this sickness when he or she is bitten by a mosquito that has contracted the virus. The insect can get it from a bird carrying the disease. The illness is not usually contagious between people. It can, however, be transmitted from a pregnant mother to her baby, or through blood transfusion.

Symptoms of this disease most frequently include fever, rash, swollen glands, vomiting, body aches, and headaches. Severe complications from West Nile encephalitis may result in disorientation, tremors, brain damage, paralysis, and unconsciousness. It generally creates the most serious problems — including death — in the elderly, young children, and those with compromised immune systems.

When West Nile encephalitis is suspected, doctors usually perform a battery of medical exams to verify the infection. A serology test, that checks the blood for antibodies of the virus, is the most common and precise way to confirm the diagnosis. Magnetic resonance imaging (MRI) or computerized tomography (CT) scans are frequently performed to analyze the impact of the infection on the brain.


The treatment for this condition is usually limited to a focus on making the patient more comfortable until the infection subsides. In severe cases and especially when neurological symptoms are present, however, hospitalization may be required. The patient is usually monitored by an infectious disease specialist, neurologist, and other healthcare professionals.

The West Nile Virus was first identified in the 1930s, and was common in the Middle East, Africa, and western Asia until the summer of 1999, when an outbreak in the United States gained national media attention there. While initial reports of the infection came from the state of New York, the disease quickly spread throughout the U.S. and Canada. During the time of the outbreak, from 1999 to 2008, more than 28,000 cases of West Nile encephalitis were reported in the United States. The epidemic increased fears among those who lived in areas where the majority of the instances occurred — mostly in the northern, western, and central territories of the country.

Since mosquitoes tend to gravitate toward water and warmth, common advice is take preventative measures to keep the bugs away when weather conditions normally attract the insects. Wearing long sleeves and pants, using mosquito repellent, and even staying indoors at dawn and dusk during warmer months is a frequent recommendation to avoid exposure. During rainy seasons in many locales, residents are urged to drain standing rain water, because it creates a breeding ground for the disease-carrying insects.



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