Although it may be getting a little cooler, the threat of West Nile Virus (WNV) does not seem to be abating and is on track to be one of the worst years on record. The Centers for Disease Control and Prevention have reported that cases are up to 4,249 as of Oct. 9, marking it as the highest number of cases since 2003. About two-thirds of cases have been reported from eight states (Texas, California, Louisiana, Mississippi, South Dakota, Michigan, Oklahoma and Illinois) and more than 30 percent have been reported from Texas alone.SymptomsWhile most people who contract WNV will not have symptoms, cancer patients with immune systems already compromised may be susceptible to these more serious symptoms, especially those with blood and lymphatic cancers, says William Schaffner, MD, of the department of preventive medicine at Vanderbilt's School of Medicine. Patients who are receiving treatment that affects their immune system may also be at higher risk of developing serious symptoms from the virus.Another issue is that it may be harder to identify WNV when its symptoms so closely resemble those associated with cancer treatment, such as headache, body aches, nausea and vomiting, and skin rash. If high fever, neck stiffness, disorientation or vision problems also surface, it may be a sign of WNV. Regardless, if you think you may have WNV, call your doctor. PreventionThe CDC has listed preventive strategies on their website, including: 1. When you are outdoors, use insect repellent containing an EPA-registered active ingredient. Follow the directions on the package.2. 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.3. Make sure you have good screens on your windows and doors to keep mosquitoes out.4. 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.Insect RepellentAlthough safety concerns regarding insect repellent may be worrisome for patients, Schaffner wants to put them at ease. It's still safer to use repellent than risk getting bitten by a mosquito. Even if the insect doesn't have WVN, the bite could lead to an open sore and infection, a greater concern for patients. If anything, use a lower-concentration repellent or a more natural-based repellent, such as oil of lemon eucalyptus. And when you come back indoors, be sure to wash your hands and arms. The CDC has a fact sheet posted on its site that lists tips for choosing and using insect repellent, and the U.S. EPA has an online tool to help you choose. If you're still wary of repellent, wear long sleeves and pants and try to stay inside at dusk or dawn. It only takes one bite from an infected mosquito, so be alert.One more bit of advice from Dr. Schaffner: With the colder weather arriving, the risk of WNV goes down, but the seasonal flu risk goes up. It's best to go ahead and get that flu vaccine now.