Health and school officials alerted families at Winston Churchill High School in Potomac on Friday that a student had been diagnosed with a form of meningitis, saying there was little risk to students but that parents should be aware of the presence of the contagious disease.

In a letter sent home with students, officials said the student was recently found to have meningococcal disease, caused by a bacteria, and was improving.

Those who had close contact with the student — sharing soda bottles or kissing, as examples — are being treated with prophylactic antibiotics, said county health spokeswoman Mary Anderson. “It’s not usually spread by casual contact,” she said.

In the letter, officials emphasized that routine classroom and school contact does not usually pose a risk and that meningitis infection is mostly spread through saliva, mucous or droplets from the nose and throat.

Parents were being warned “in an abundance of caution,” the letter said. Symptoms of infection include chills, high fever, vomiting, headache, stiff neck and rash.

If students develop such conditions before May 13, the letter said, parents should immediately consult a doctor. If left untreated, the disease can be serious and sometimes fatal, according to a state health fact sheet.

“There’s a very low risk of transmittal,” said schools spokesman Dana Tofig. “But if students exhibit any other symptoms, they should call their doctor or the Department of Health as quickly as possible.”