Refusal to refund event deposit in the face of the Coronavirus

I gave a deposit of $400 to a host for a birthday party. They agree to refund in case of a storm in a Facebook post. Days before the party, the coronavirus spread to our area. At the recommendation of the World Health Organization to avoid public gatherings, I cancelled the event. They will not refund me because it is not a storm, but a virus. What are my options in this case? The host is a private owner of a property (their home/ranch). Their is no written agreement between us in this case.