The Centers for Disease Control and Prevention announced this week that West Nile Virus cases are up 40 percent from last week.

Last week, the CDC reported that reported cases of West Nile Virus are at an all-time high.

While Illinois does not rank among the top five states in terms of cases, there have been 21 reported human cases of West Nile Virus in Illinois as of Aug. 21. Those cases have been clustered in the Chicago area, with 13 human cases in Cook County and one in Lake County.

In the map above, Patch charted both cases of West Nile Virus confirmed in both humans and mosquitoes, according to our reporting. You can read the coverage from the western part of the area here. For coverage closer to the lake, click here.

The CDC lists the following as symptoms of West Nile Virus:

• Serious Symptoms in a Few People. About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

• Milder Symptoms in Some People. Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks.

• No Symptoms in Most People. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all.

And here are the organization’s recommendations on how to avoid getting sick in the first place:

• When you are outdoors, use insect repellent containing an EPA-registered active ingredient. Follow the directions on the package.
• Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.
• Make sure you have good screens on your windows and doors to keep mosquitoes out.
• Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Keep children's wading pools empty and on their sides when they aren't being used.