This used to be a typical childhood illness for baby boomers although, as an adult, I think it can have very bad health risks, especially for men.
Yes , highly infectious -
Mumps can lead to infertility in men if contracted post puberty
Even those who have been immunized, may need a booster.
Of the 31 members of the SUNY New Paltz swim team, all had already been previously immunized . Unfortunate timing for possible spreading the infection around Thanksgiving and Christmas holidays - possibly putting other family members at risk.
I’ve heard in adult males, it can cause sterility.
I had it as a kid.