An investigation into a mumps outbreak has shut down a bar on the Jersey Shore. After visiting D’Jais Bar and Grill in Belmar, N.J., 21 people have reported mumps-like symptoms, which prompted health officials to release a statement on Thursday.

Mumps is a viral infection that was common in the United States until vaccination became routine. It primarily affects the parotid glands, one of the three saliva-producing glands that sit just below and in front of your ears. The vaccination was first licensed in the U.S. in 1967. By 2005, childhood vaccination coverage reduced the disease rate by 99 percent. Before the two-dose routine vaccination program was introduced, mumps was a common illness in infants, children, and young adults.

The recent outbreak was first reported on Wednesday, prompting Monmouth County Health Department to step in and investigate.

“The medical professional advised these individuals to be on bed rest, increase their fluid intake and take steps to reduce their fever,” Michael Meddis, the country’s public health coordinator, said in a statement.

Mumps is highly contagious and often starts showing symptoms within a few days, including fever, headaches, muscle aches, tiredness, loss of appetite, and swelling of the salivary glands, according to the Centers for Disease Control and Prevention (CDC). It is spread through tiny droplets of saliva or mucus and is usually contracted when an infected person cough, sneezes, talks, or shares a drink with another person. Touching a contaminated surface that was touched by someone with mumps and then rubbing the mouth or nose can also transmit the condition.

The CDC has provided a preventative measures list for the public to follow, especially during an outbreak:

  1. Minimize contact with others, especially babies and those with weakened immune systems.
  2. If glands around the ears begin to swell, stay home from work or school for at least five days and avoid contact with other members of the household.
  3. Use a tissue to cover mouth and nose if you have to cough or sneeze and then properly dispose of it afterwards. Never sneeze or cough into your hands, but use upper sleeve if necessary.
  4. Practice proper hygiene and wash hands with soap and warm water.
  5. Never share drinks or utensils.
  6. Clean surfaces with soap and water or cleaning wipes routinely.

According to D’Jais's co-owner, Frank Sementa, some of this employees started to feel sick over the weekend. “The employees went to the doctors and then all of a sudden it became, well gee, they’re saying we may have the mumps,” Sementa told Fox News.

“This matter is being handled with great concern and sensitivity by the owners of D’Jais, the Borough and the County of Monmouth,” Belmar Administrator Colleen Connolly said in a statement. “D’Jais and the County of Monmouth are working together on ensuring that workers and patrons are safe and will follow all necessary protocols to ensure the matter is handled responsibly. Nothing is more important that the health and well being of our residents.”