Two Texas State University students have been diagnosed with mumps and another two possibly have it as well, according to an email sent out by the university Tuesday morning.

The Hays County Local Health Department confirmed the cases with the school. “Three cases are related due to close contact,” according to the letter. A spokesperson for the school says the three are close friends. 

The school says it is working with the health officials to identify people who may have had contact with the students who have mumps. 

Last summer, the University of Texas at Austin saw a mumps outbreak that affected seven students. 

The virus is transmitted through coughing, sneezing, kissing, sharing items such as cups or touching contaminated surfaces. 

The Texas Department of State Health Services says mumps symptoms include swollen or tender salivary glands, swollen or tender testicles, low fever, tiredness and muscle aches. Symptoms become present 16-18 days after being exposed to the virus, but can appear as late as 25 days.

Mumps cases in Texas reached a 20-year high in 2017. The state says the best way to prevent getting sick is by getting vaccinated, covering coughs and sneezes, washing your hands frequently and not sharing food and drink.