Chances are you’ve been hearing a lot about mumps lately.  If you live in the greater Boston area, The Boston Globe reports that Harvard has been hit the hardest with 13 confirmed cases.  The grand total for Massachusetts so far in 2016 stands at 26 cases (and all of the U.S. at 250 cases).  As we barrel towards peak season for mumps, these numbers are alarming.  So what’s with all the mumps?

Mumps is a viral infection that is easily spread person-to-person by respiratory droplets, saliva, and fomites (things you touch).  It is a near perfect pathogen to spread throughout tightly packed college dorms.  The illness is typically a standard upper respiratory tract disease with about 2/3 of patients developing the hallmark of largely swollen glands in the jaw and neck (see picture below).

Cases of mumps dropped precipitously in the 1970s after the development of the Jeryl Lynn Merck vaccine in 1965 and its introduction into the combination MMR (measles, mumps, rubella) vaccine in 1971. The Centers for Disease Control and Prevention (CDC) recommend MMR vaccination for kids at 1 year and a booster between 4-6 years.  The newer MMRV (MMR + varicella [chicken pox]) is now the preferred combo, but the current cases of mumps around the U.S. are in young adults who would have been offered the standard MMR as kids in the 90s.

The state of Massachusetts requires all full-time college students to provide records of both doses of MMR and it’s been reported that vaccination has been confirmed for most of the current cases in Boston.  In fact, most of the recent outbreaks in the U.S. involve young adults who had received their childhood vaccinations.  So why are these students getting mumps?

Just like natural immunity, vaccine immunity is not equal in every person and some individuals–for a variety of reasons–don’t develop the antibodies necessary to protect them from the disease.  It is estimated that 78% of kids develop sufficient “protective” mumps-specific antibodies after 1 dose of MMR and 88% after 2 doses.  In addition, the level of antibodies in any given person wanes with time.  Both of these factors contribute to the ability of the mumps virus to persist and to cause isolated outbreaks each year.

Colleges have always been hotbeds for infectious disease.  From living in close quarters to sharing facilities, beer cans, and joints, pathogens jump happily about college students.  But it appears that we might be in the midst of an upward trend in mumps infections since 2014 (see table from CDC).  Here are a few hypotheses why:

1.  The efficacy of the vaccine after 2 doses is equal to the threshold for herd immunity,  meaning that the impact of more parents deferring vaccination of their kids (for medical or other reasons) is more strongly felt by the community.  Even though many of these cases have occurred in students who were vaccinated, increasing levels of unvaccinated individuals allows more virus to persist.
2. Increased travel of college students to places such as Africa or Southeast Asia may permit passage of the virus from regions without standard mumps-containing vaccines back to their dorms.
3. The virus may have mutated away from the vaccine strain making the antibodies less effective at protecting us.  So even if you’re in the 88% of people with mumps-specific antibodies, those antibodies might not work as well anymore.
4. Similarly, partial immunity may confer just enough protection to conceal mumps, making it appear similar to any old common cold, and limit institution of effective quarantine procedures.

I’ve been sick with what appears to be a common cold over the past week.  What started as a cough and sore throat has evolved into a relentlessly runny nose. I don’t work on a college campus and I don’t have swollen salivary glands, so I’m pretty certain that I do not have mumps.  However, in the early stages of this illness I stayed home, quarantining myself from others in my office, stores, events, and public transportation.  During this illness, I have also judiciously used alcohol-based hand sanitizer.  I’ve washed my hands before and after using the restroom.  Remember those fomites?  Those include public restroom stall doors, locks, tissue dispensers, and toilet handles–things you touch before washing your hands.  I can’t guarantee that this illness ends with me, but I will do everything in my power to prevent the spread to those around me.

MMR vaccination is still the best way to protect against mumps, but you can do a lot to prevent the spread of many infectious diseases, including mumps, with healthy hygiene.  Wash your hands frequently, do not share anything with others that touches your face or mouth (drinks, eating utensils, etc), disinfect surfaces that you touch (and your hands), and cover your nose and mouth with a tissue or your inner elbow when you cough or sneeze.  And please, please, please stay home while you are sick if you can.

References:
1. DynaMed Plus. Ipswich (MA): EBSCO Information Services. Record No 114737, Mumps: updated 2015 Sep 08.
2.  Vaccines 6th Ed. Plotkin SA, Orenstein WA, Offit PA. Elsevier Inc. 2013.
3.  Centers for Disease Control and Prevention: Mumps
4.  Massachusetts school immunization records for school year 2015-2016