Testicular immunology
Mumps is a viral disease which causes swelling of the salivary glands and testes. The mumps virus lives in the upper respiratory tract and spreads through direct contact with saliva. Prior to widespread vaccination programs, it was a common childhood disease. Mumps is generally not serious in children, but in adults, where sperm have matured in the testis, it can cause more severe complications, such as infertility.
Impacts of tourism
Examples of invasive species spread by tourism:
-Bigheaded ant (Pheidole megacephala): Is one of the worst invasives and classified under the “worlds 100 worst” invasive species. Originally found in the Galapagos islands in 2007 within ship cargo for tourist supplies. Ants can be spread with the movement of people from one island to another. 
-Cheatgrass (Bromus tectorum): Spread fast, don’t allow native species to grow, can cause forest fires to spread rapidly. Can be carried by people through shoes and gear, pets and other animals can spread the seeds through their travel as well. 
-Zebra Mussels (Dreissena polymorpha): These are believed to have come from the Caspian Sea in Europe in a ships ballast water. They are spread by uncleansed boats from one body of water to another as tourists move to different locations.