Mumps

I’ve intended to write about mumps for nearly a year. Parenting and bicycle riding have taken my time and attention away from this blog. More about that later.

 

It was about this time last year that our mumps epidemic started. Over a four month period we had 59 confirmed and probable mumps cases. We investigated an additional 118 suspect cases and 52 people who did not meet one of those three classifications and were ruled out for mumps. That and a bad influenza season kept my colleagues and me busy! Other jurisdictions had far more cases than we did. King and Spokane counties in Washington State each had more than 300 confirmed and probable cases. Arkansas had nearly 3,000 cases.

 

Mumps is a viral disease characterized by swelling of the parotid salivary glands, which are on the side of the face in front of the ear. One or both parotid glands may be swollen and sometimes other salivary glands are swollen. The parotid gland may become so large that the swelling covers jawline extends to the neck.

 



CDC

 



CDC

The photographs above are from the Center for Disease Control and Prevention (CDC) Public Health Image Library. The first shows "characteristic swollen neck region." This is the photograph that is on the CDC's mumps webpage. The caption of the second photograph reads, "cervical [neck] swelling due to enlargement of the submaxillary salivary glands." What is not clear in either of these photographs is swelling of the salivary glands on the side of the face. The submaxillary glands are under the jaw and can be swollen with mumps, but it's rare that swelling of other salivary glands occurs without swelling of the parotid glands. Neck swelling can be caused by inflamed lymph nodes (lymphadenopathy), so not everything that looks like mumps is mumps.

 

Other symptoms of mumps include orchitis (painful swelling of the testicles), oophoritis (painful swelling of the ovaries), meningitis, and encephalitis. In fact, before the vaccine was developed, mumps virus was the most common cause of encephalitis in the United States. Permanent deafness in one ear is an uncommon complication of mumps. About one third of people infected with mumps virus have no symptoms but can still transmit it to others.

 

Parotitis can be caused by other things, including bacteria and other viruses. When mumps virus is not circulating in a community, sporadic cases of parotitis are likely to be caused by a virus other than mumps. There are also non-infectious causes of parotitis. Again, not everything that looks like mumps is mumps.

 

Mumps is the second M in MMR: measles, mumps, and rubella vaccine. Mumps outbreaks are uncommon in the U.S. because most states require children to have two doses of MMR by the time they start kindergarten. A few states require only measles vaccine or measles and rubella vaccine but, because MMR and MMRV (varicella: chickenpox) are the only measles-containing vaccines licensed in the U.S., most children in this country have received two doses of mumps vaccine by the time they start kindergarten.

 

So, why do we have mumps outbreaks in the U.S.? As I wrote before, no vaccine is 100% effective. A single dose of mumps vaccine is around 78% effective at preventing mumps. Two doses is about 88% effective. There is also evidence that immunity from mumps vaccine wanes over time. Outbreaks usually occur in places where people live in close contact with each other like military barracks or college dorms. Mumps is transmitted by respiratory droplets, contact with people infected with the virus, and contact with objects that are contaminated with the virus (fomites).

 

Respiratory droplets (CDC/ Brian Judd)

I can’t say how effective MMR was at preventing mumps in Pierce County. As I wrote in my post on attack ratios, I need the denominators: the number of vaccinated people exposed to the virus and the number of unvaccinated people exposed to the virus. I also don’t have the numerators. Immunization records are available for most children in Pierce County but frequently not available for adults. What I can say is that very few cases of mumps could be attributed to transmission in schools in Pierce County. Most of our cases were linked to another person with mumps living in the same house or transmission in a setting other than a school in Pierce County, e.g., workplaces or schools in the Auburn School District where there was a large outbreak.

 

“MMR is banned in Japan!”

 

Not exactly.

 

A different mumps virus was included in the Japanese MMR. The Urabe AM9 mumps vaccine was associated with higher incidence of viral meningitis. Although viral meningitis is usually self-limiting and does not result in longterm problems, Japan now uses a measles and rubella (MR) combination vaccine without a mumps component. No increased risk of viral meningitis has been found with the Jeryl Lynn strain, the virus used in the MMR and MMRV vaccines license in the U.S. Incidentally, both viruses are named after the children from whom the viruses were taken. Jeryl Lynn is the daughter of Dr. Maurice Hilleman, who developed over 40 vaccines, including mumps.

 

Andrew started kindergarten this year.

 

 

 

 

 

More information:

 

CDC: Mumps cases and outbreaks

 

References:

 

Barskey, A. E., Juieng, P., Whitaker, B. L., Erdman, D. D., Oberste, M. S., Chern, S. W. et al. (2013). Viruses detected among sporadic cases of parotitis, United States, 2009-2011. Journal of Infectious Diseases, 208(12), doi:10.1093/infdis/jit408.

 

Campbell, J. R. (2014) Parotitis. In J. D. Cherry, G. J. Harrison, & S. L. Kaplan (Eds.) Feigin and Cherry’s textbook of pediatric infectious diseases, 7^th Ed. [Electronic version]: Saunders.

 

Davidkin, I., Jokinen, S., Paananen, A., & Peltola, H. (2005). Etiology of mumps-like illnesses in children and adolescents vaccinated for measles, mumps, and rubella. Journal of Infectious Diseases, 191(5), doi:10.1086/427338.

 

Hatchette, T. F,. Mahony, J. B., Chong, S., & LeBlanc, J. J. (2009). Difficulty with mumps diagnosis: What is the contribution of mumps mimickers? Journal of Clinical Virology, 46(4), doi:10.1016/j.jcv.2009.09.024.

 

Litman, N. & Baum, S. G. (2015). Mumps virus. In J. E. Bennett, R. Dolin, & M. J. Blaser (Eds). Mandell, Douglas, and Bennett's principles and practice of infectious diseases, 8^th Ed. [Electronic version]. Saunders.

 

Parker Fiebelkorn, A., Barskey, A., Hickman, C,. & Bellini, W. (2012). Mumps. In S. W. Roush & L. M Baldy (Eds.) Manual for the surveillance of vaccine-preventable diseases, 5^th Ed. [Electronic version]. Center for Disease Control and Prevention.

 

Rubin, S. A. & Plotkin, S. A. (2018). Mumps vaccine. In S. A. Plotkin, W. A. Orenstein, P. A. Offit., & K. M. Edwards (Eds.). Vaccines, 7^th Ed. [Electronic version] Elsevier.