A number of staff members on one of Goldman Sachs' trading floors showed signs of mumps this week.

The Wall Street investment bank has been telling staff to get shots or visit the firm's health center if they didn't receive the vaccine during childhood.

Goldman Sachs is battling to contain a rare but contagious flare-up of mumps after a few employees contracted the disease.

Employees on one of its trading floors showed signs of the disease this week and the firm told people to get shots or visit the firm's health center if they didn't receive the vaccine during childhood, according to a person with knowledge of the matter who asked to remain anonymous discussing internal conditions.

Goldman's health center was administering the mumps vaccine for free on Friday.

A Goldman spokeswoman declined to comment.

Mumps is caused by a virus and considered quite contagious. Symptoms usually involve fever, headache, muscle aches, exhaustion, and reduced appetite, according to the Centers for Disease Control and Prevention. Those signs usually give way to a swelling of the salivary glands, puffy cheeks, and a swollen jaw, according to the agency's website.

Before a vaccination program started in 1967, about 186,000 cases were reported in the US each year, according to the CDC. Now, most children receive the vaccine in a series of shots, with one given in the first year of life and another administered around the time they begin school. Since the program began, there's been a 99% reduction in the incidence.

Even so, outbreaks do still occur. In 2014, members of the Pittsburgh Penguins hockey team came down with the disease. And in the developing world, where some of Goldman's employees were born or spent their childhood, vaccination programs are much less comprehensive.