Well slightly jealous of your holiday (but at least I'm off to Mull and Skye in a few weeks) but had a similar situation on our Easter holiday in Wales. I had what I thought was my usual hay fever but MrsS went down with a sore throat etc. When we got home, we tested and were both positive. However, we were clear a couple of days later and the following weekend did the the great Birmingham run. Not sure how or when we got infected but I guess you never do. Other than a couple of co-op visits, we generally keep ourselves to ourselves and in the campervan, contact with others is minimal.