The United States is facing a potential increase in mumps cases, alongside a broader resurgence of vaccine-preventable diseases like measles. While measles outbreaks in states such as South Carolina dominate current headlines, public health officials are monitoring mumps closely. By the end of February 2026, the CDC reported 34 cases this year, including a significant spike in Maryland, which saw 19 confirmed and 7 probable cases – a sharp increase from just 4 in all of 2025.
This rise, though still relatively small in overall numbers, is a reminder that mumps remains present in the U.S. and can spread efficiently, particularly in densely populated environments such as schools and universities.
Why Mumps Persists Despite Vaccination
Mumps outbreaks are driven by several factors, including declining vaccination rates in some communities and the imperfect efficacy of the MMR vaccine. The MMR vaccine protects against measles, mumps, and rubella. Before its introduction in 1967, most children contracted mumps by adolescence. The vaccine dramatically reduced cases, dropping them from approximately 150,000 in 1968 to around 230 by 2003. However, herd immunity thresholds are more challenging to achieve with mumps compared to measles because the vaccine is less effective.
“A single dose of the MMR vaccine provides about 72 percent protection, while two doses increase that to approximately 86 percent,” explains Christy Beneri, DO, assistant medical director of infection prevention at Stony Brook Children’s Hospital. This means some vaccinated individuals may still contract the illness, a phenomenon called breakthrough infection. Waning immunity over time also contributes to cases in older adolescents and adults.
Yvonne Maldonado, MD, a professor of pediatrics at Stanford University, summarizes the situation: “Current cases may result from a combination of undervaccination and the lower effectiveness of the mumps vaccine.”
Recognizing Mumps Symptoms and How It Spreads
The primary symptom of mumps is inflammation of the salivary glands, causing pain and swelling, particularly near the jawline. Other symptoms include fever, headache, muscle aches, fatigue, and loss of appetite. Teens and adults tend to experience more noticeable symptoms than young children.
The virus spreads through saliva and respiratory droplets when an infected person coughs, sneezes, or shares utensils. People can spread the virus up to two days before symptoms develop, making containment difficult. Some individuals may experience mild or no symptoms but still transmit the disease.
The Risks of Mumps Infection
While most mumps cases resolve with rest and fluids, complications can occur, especially in adults, unvaccinated individuals, and those with weakened immune systems. The most common complication is orchitis – inflammation of the testicles – which can potentially lead to testicular atrophy and fertility issues. Other severe complications include meningitis, encephalitis, pancreatitis, and hearing loss.
Vaccination: The Best Defense
The American Academy of Pediatrics recommends two doses of the MMR or MMRV vaccine: the first between 12 and 15 months, and the second between 4 and 6 years. Additional doses are not routinely recommended, but public health authorities may suggest boosters during outbreaks for high-risk individuals.
If you are unsure of your vaccination status, consult your healthcare provider. Blood tests can determine if you have protective antibodies from previous immunization.
Preventing Transmission
Vaccination remains the most effective prevention method. Alongside vaccination, simple practices can reduce spread: avoid sharing drinks or utensils, wash hands frequently, and stay home if sick.
The resurgence of mumps underscores the ongoing importance of vaccination in protecting both individual and community health. Maintaining high vaccination rates is essential to prevent further outbreaks and mitigate the risks associated with this preventable disease.
