According to the Environmental Protection Agency (EPA) whole house fans can help protect people indoors from airborne transmission of COVID-19 because they increase ventilation with outside air to cool indoor spaces. When used along with other best practices recommended by the Centers for Disease Control and Prevention, operating a an attic house fan can be part of a plan to protect yourself and your family.
https://www.epa.gov/coronavirus/indoor-air-homes-and-coronavirus-covid-19#evaporative