Although woods and trails provide some distance from people, they are home to other dangers — such as ticks that carry bacteria-causing Lyme disease or mosquitoes that transmit West Nile virus — especially now, when bugs are proliferating. These and other insects can pass along potentially serious diseases with a single bite.

Health departments have been spending their budgets and deploying personnel on covid-19 efforts, which hurts their ability to focus on programs that control mosquitoes and ticks, says Chelsea Gridley-Smith, director of environmental health for the National Association of County and City Health Officials.