The number of human West Nile virus (WNV) cases reported to the Centers for Disease Control and Prevention (CDC) shot up over the past week seeing an increase in over 50 cases.

As of August 4, 2015, 90 cases of West Nile virus disease in people have been reported to CDC.This is up from 36 cases reported on July 28.

In addition, Arizona, California and Texas have all reported fatalities due to infection with the mosquito borne virus.

Arizona has reported the most cases to date (17) or 19 percent of the national total.


In 2014, 2,205 human WNV cases were reported with California leading the nation with 801 cases.

West Nile virus was first detected in North America in 1999, and has since spread across the continental United States and Canada.

What are the symptoms of West Nile virus disease? The CDC breaks it down by severity:

No symptoms in most people. Most people (70-80%) who become infected with West Nile virus do not develop any symptoms.

Febrile illness in some people. About 1 in 5 people who are infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.

Severe symptoms in a few people. Less than 1% of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues). The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis.

Recovery from severe disease may take several weeks or months. Some of the neurologic effects may be permanent. About 10 percent of people who develop neurologic infection due to West Nile virus will die.

People over 60 years of age are at the greatest risk for severe disease. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk for serious illness.

Neuroinvasive (severe) disease cases have been reported to CDC ArboNET from the following states for 2015: Alabama, Arizona, Arkansas, California, Colorado, Florida, Idaho, Kansas, Louisiana, Mississippi, Montana, New Mexico, Ohio, Oklahoma, Pennsylvania, Tennessee, Texas, Virginia, and Washington for a total of 50 cases.

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