Mumps is a highly contagious viral disease that continues to be a public health concern in the United States. While largely controlled through widespread vaccination efforts, cases of mumps still occur across the country. Understanding its nature and persistence is important for public awareness and prevention.
Understanding Mumps
Mumps is a viral infection caused by a paramyxovirus, characterized by painful swelling of the salivary glands, particularly the parotid glands located between the ear and the jaw. Other common symptoms include fever, headache, muscle aches, fatigue, and loss of appetite, often appearing a few days before the salivary gland swelling. Parotid gland swelling may be unilateral or bilateral, with about 25% of cases affecting only one side.
The virus spreads through respiratory droplets from coughing or sneezing, and direct contact with infected saliva. People infected with mumps are most contagious from two days before symptoms appear until five days after the onset of salivary gland swelling. The incubation period, the time between exposure to the virus and the appearance of initial symptoms, usually ranges from 12 to 25 days, with an average of 16 to 18 days. Some individuals might experience very mild symptoms or no symptoms at all, yet can still transmit the virus.
Mumps Incidence in the US
Despite the success of the mumps vaccination program, which began in 1967, leading to a more than 99% decrease in cases, mumps continues to occur in the United States. Cases decreased significantly after the vaccine became available, from 152,209 in 1968 to 231 in 2003. Since 2006, however, reported cases and outbreaks have increased, with the number of cases ranging from a few hundred to several thousand annually. From 2018 to 2023, 8,006 confirmed and probable mumps cases were reported.
Mumps cases often manifest as localized outbreaks rather than widespread epidemics. These outbreaks frequently occur in settings with intense or frequent close contact, such as college campuses, close-knit communities, and correctional facilities. During 2018-2020, the incidence of mumps was highest among individuals aged 18-24 years. While cases decreased in 2020, possibly due to social distancing measures during the COVID-19 pandemic, the virus continued to circulate.
Factors Influencing Mumps Presence
Mumps persists in the U.S. due to several interacting factors, even with high vaccination rates. The measles, mumps, and rubella (MMR) vaccine is highly effective; two doses provide an estimated 86% protection against mumps (ranging from 32% to 95%). Vaccine-derived immunity can wane over time, especially with high virus exposure. Protection can wane an average of 27 years post-vaccination.
Gaps in vaccination coverage also contribute to the ongoing presence of mumps. Pockets of unvaccinated individuals or communities with lower vaccination rates create opportunities for the virus to spread. While recent large outbreaks have occurred in highly vaccinated populations, a lack of full vaccination in some areas still contributes to transmission. In 2024-25, childhood MMR vaccination rates fell to 92.5% for kindergarteners, leaving a segment vulnerable.
Close-contact settings facilitate the transmission of mumps. Environments like college dormitories, sports teams, and other communal living situations allow the virus to spread quickly, even among vaccinated individuals. The mumps virus can spread before symptoms appear, complicating containment in these settings. This allows for silent transmission, contributing to outbreaks.
Preventing Mumps and Responding to Cases
Vaccination with the MMR vaccine remains the most effective preventive measure against mumps. The Centers for Disease Control and Prevention (CDC) recommends two doses: the first at 12-15 months, and the second at 4-6 years, typically before school entry. Two doses of the MMR vaccine offer long-term protection, significantly reducing infection risk and mitigating symptom severity and complications.
Public health authorities implement strategies when mumps cases are identified. These include investigating suspected cases, isolating infected individuals for five days after symptom onset, and identifying close contacts. In outbreak settings, public health officials may recommend an additional, third MMR vaccine dose for high-risk groups like college students or those in close-knit communities. This booster enhances protection where exposure is intense.
Individual actions also prevent mumps transmission. Practicing good hygiene, such as frequent handwashing and covering coughs and sneezes, limits viral spread. Staying home from work or school for five days after symptom onset prevents further transmission. If mumps is suspected, consult a healthcare provider for diagnosis and guidance. While most recover fully, potential complications like inflammation of the testicles or ovaries, meningitis, or, rarely, hearing loss, underscore the importance of these preventive measures.