They say the rugby player was exposed to the disease during a rugby tournament in April. The state Department of Health and Human Services said Thursday the 21-year-old player developed symptoms earlier this week.
Officials say the man was probably infected after interacting with members of an English rugby team that was traveling in the area in April.
Officials say one English player has been diagnosed with mumps. Four others have developed symptoms.
The mumps virus is spread by coughing and sneezing. The most common symptoms are fever, headache and swollen glands. It can lead to hearing loss, meningitis and testicular damage that can result in sterility.