First cases of human West Nile virus in 2018 confirmed

A Chicago resident has been confirmed as the first person in Illinois this year to have contracted mosquito-borne West Nile virus, according to the Illinois Department of Public Health.

The woman, who is in her 60s, contracted the virus and become sick in mid-May, IDPH reported Wednesday. The agency is urging residents to be aware of their surroundings and take preventative measures.

"West Nile virus can cause serious illness in some people so it’s important that you take precautions like wearing insect repellent and getting rid of stagnant water around your home," Dr. Nirav D. Shah, director of the Illinois Department of Public Health, said in a statement.

No vaccine or specific antiviral treatment for West Nile virus exists, and people with weak immune systems, health conditions, and people older than 60 could be at higher risk for severe illness if they contract the virus, according to the U.S. Centers for Disease Control and Prevention.

In mid-June, the California Department of Public Health announced its first West Nile virus cases.

These first cases of West Nile virus are earlier than those of the first reported cases in 2017.

In 2017, the first human case of West Nile was reported just over a month later, on July 20.

California public health officials have said they believe the cases will increase and precautions remain important.

"West Nile virus activity in the state is increasing, so I urge Californians to take every possible precaution to protect against mosquito bites," said CDPH Director and State Public Health Officer Dr. Karen Smith.

There were 2,002 reported cases of West Nile Virus and 121 deaths across the U.S. in 2017, according to the CDC.

Even though the virus was found in 47 states and the District of Columbia in 2017, the highest number of cases and deaths were reported in California, Texas and Arizona, according to CDC data.

Illinois ranked fourth, followed by South Dakota, Nebraska, Mississippi, Utah and New York respectively.

The virus is passed on through the bites of Culex Pipiens mosquitoes, also known as house mosquitoes, IDPH said. After the virus is transmitted, one out of five people infected could experience symptoms such as fever, muscle aches, headache and nausea for a few weeks or months. In rare severe case, the symptoms are meningitis, encephalitis or death, according to IDPH.

Mosquitoes become infected with the West Nile Virus by biting birds that may have contracted the virus, according to CDC.

West Nile virus was first detected in the U.S. in 1999.