PHOENIX -- The United States is experiencing its biggest spike in West Nile virus since 2004. Be aware of the West Nile virus activity in your area and take preventive action to protect your family.The virus is transmitted through infected mosquitoes and most infections occur between June and September, and peak in August, according to the Centers for Disease Control and Prevention.The symptoms include fever, headache, body aches, joint pains, vomiting, diarrhea and rash. Less than 1 percent develop a serious illness such as encephalitis or meningitis. People over 50 and those with cancer, diabetes and kidney disease are at greater risk.There are no medications to treat it or vaccines to prevent it. Most people with milder illnesses recover on their own.Most importantly, prevention measures include avoiding mosquito bites, using insect repellent and getting rid of insect breeding sites, such as pools of stagnant water.