A Striking Surge in Cases
Public health officials in Maryland are closely monitoring what has become a dramatic increase in mumps infections. As of mid-February 2026, the state has documented 26 cases of mumps, comprising 19 confirmed and 7 probable cases. To put that number in perspective, the entire state recorded only four mumps cases throughout all of 2025, meaning the current figure represents more than a sixfold increase in a fraction of the time.
The concentration of cases in the Baltimore metropolitan area has prompted local and state health departments to investigate whether the infections are epidemiologically linked. While the specific cause of the surge remains under active investigation, the numbers have drawn attention from public health experts across the region and raised questions about mumps vulnerability even in well-vaccinated populations.
Mumps in a Vaccinated Population
Perhaps the most notable aspect of the Maryland outbreak is that the majority of infected individuals had previously received the measles-mumps-rubella (MMR) vaccine. This detail, while concerning at first glance, aligns with what scientists have long known about the vaccine's effectiveness against mumps specifically.
The MMR vaccine is approximately 85 percent effective against mumps when both recommended doses have been administered. While this level of protection is substantial, it means that roughly one in seven fully vaccinated individuals remains susceptible to infection. In contrast, the same vaccine provides approximately 97 percent protection against measles and 97 percent protection against rubella.
This effectiveness gap is not a new revelation, but it becomes highly visible during outbreaks. When mumps circulates in environments where people have close, prolonged contact, even vaccinated individuals can contract and transmit the virus. College campuses, sports teams, and workplaces have historically been common settings for mumps outbreaks in vaccinated populations.
How Mumps Spreads
Mumps is caused by a paramyxovirus that spreads primarily through respiratory droplets and saliva. Coughing, sneezing, talking, and sharing eating utensils or cups can all facilitate transmission. The virus is particularly efficient at spreading among people who spend time in close proximity, generally within three to four feet of an infected person.
The disease has an incubation period of roughly 16 to 18 days, though it can range from 12 to 25 days. Infected individuals are contagious from about two days before symptoms appear until approximately five days after symptom onset. This pre-symptomatic contagious period makes containment challenging, as people can unknowingly spread the virus before they realize they are sick.
Common symptoms include:
- Swelling of the parotid glands, which causes the characteristic puffy cheeks and jaw pain associated with mumps
- Fever, headache, and muscle aches
- Fatigue and loss of appetite
- Pain while chewing or swallowing
While mumps is generally a mild illness in children, it can cause serious complications in adolescents and adults, including inflammation of the testicles or ovaries, meningitis, encephalitis, and hearing loss.
Public Health Response
The Maryland Department of Health has stated that the overall risk to the public is considered low given Maryland's high vaccination rate. Nonetheless, health officials are taking the outbreak seriously and have implemented several response measures.
State and local health departments are working to determine whether the 26 cases are interconnected or represent multiple independent transmission chains. Contact tracing efforts are underway in the Baltimore area to identify exposed individuals and monitor them for symptoms.
Emergency medical personnel in the region have been advised to use comprehensive protective equipment, including masks, gowns, gloves, and eye protection, when evaluating patients with suspected mumps. Clinicians have been reminded to maintain a high index of suspicion for mumps in patients presenting with parotitis, the clinical term for swollen salivary glands, and to report suspected cases promptly.
The Centers for Disease Control and Prevention continues to recommend that all children receive two doses of the MMR vaccine, the first at 12 to 15 months of age and the second at four to six years. In outbreak settings, health authorities sometimes recommend a third booster dose for individuals who may have waning immunity.
National Context
Maryland's surge comes against a backdrop of scattered mumps activity across the United States. At the end of January 2026, at least five other states had reported mumps cases, though none had exceeded three cases at that point. Maryland's numbers are significantly higher than those in any other state, making it the focal point of national attention regarding mumps in early 2026.
Mumps was once one of the most common childhood diseases in the United States, with hundreds of thousands of cases reported annually before the introduction of the MMR vaccine in 1967. Vaccination campaigns reduced cases by more than 99 percent, but the disease has never been fully eradicated. Periodic outbreaks continue to occur, often in settings where people live, work, or socialize in close quarters.
In recent years, researchers have explored whether waning immunity from childhood vaccination contributes to adult susceptibility. Studies have shown that the protective effect of the MMR vaccine against mumps diminishes over time, which may partially explain why outbreaks tend to affect young adults who received their last dose a decade or more earlier.
What Residents Should Know
Health officials emphasize that vaccination remains the most effective defense against mumps, even though breakthrough infections can occur. Individuals who are unsure of their vaccination status are encouraged to consult their healthcare providers and ensure they are up to date on their MMR immunizations.
Basic hygiene practices also reduce transmission risk. Frequent handwashing, avoiding the sharing of drinks or eating utensils, and covering the mouth when coughing or sneezing can all help limit the spread of respiratory viruses including mumps.
People experiencing symptoms consistent with mumps, particularly facial swelling near the jaw line accompanied by fever, should contact their healthcare provider for evaluation and testing. Self-isolation during the contagious period is important for preventing further spread within households and communities.
This article is based on reporting by Medical Xpress. Read the original article.
