BOSTON -- Boston health officials are investigating an outbreak of mumps at Northeastern University.

They said four students who recently returned from a trip to Ireland have been confirmed as having mumps. They are all being treated.

Authorities said there has been an outbreak of the disease in Ireland where the students had been traveling.

The Dublin City University newspaper said there were more than 800 cases of mumps reported at Irish colleges and universities this year alone.

Mumps is a respiratory virus that is spread through coughing or saliva. Some of the most common symptoms are fever, headache, muscle aches, tiredness, and loss of appetite, followed by swelling of salivary glands, according to the Centers For Disease Control and Prevention. The parotid salivary glands are most frequently affected.