Four Northeastern University students have suspected cases of the mumps, Boston public health officials said yesterday, urging any unvaccinated students and staff to get immunized against this once-common childhood illness.
Though laboratory results are not yet back to confirm the diagnosis, Dr. Anita Barry, director of infectious diseases at the Boston Public Health Commission, said the four students - two of whom had just returned from Ireland where there was a recent mumps outbreak - have symptoms consistent with mumps. Given the relative ease with which the illness can be spread, she said, "it's likely we'll see more cases."
Mumps is caused by a virus that is spread through infected respiratory tract secretions, and people typically catch it by being within 3 to 6 feet of an infected person who coughs or sneezes. However, it is difficult to tell whether someone is infectious.
Barry said people are generally considered to be infectious from three days before until five days after the onset of swelling of the salivary glands. She said most infected people feel sick for a few days with low-grade fever and "look like chipmunks."
The incubation period for mumps is usually 16 to 18 days, meaning it takes that long for symptoms to appear after someone has been exposed to the virus. But as many as 1 in 3 people infected with the mumps virus show no symptoms at all.
Serious complications are rare, but mumps has been known in rare cases to cause hearing loss in children.
The mumps vaccine does not always protect against the illness. Barry said all four sick Northeastern students have medical records showing that they had the two recommended doses of mumps vaccine. Barry said roughly 10 or 20 percent of those who receive the mumps vaccine are still vulnerable to the illness.
Patricia Wen can be reached at wen@globe.com. 
