Neighboring Texas communities are in the throes of a brewing mumps outbreak where the virus tally jumped from a reported 10 cases to 28 in less than a week. The majority of the diagnosed are school-age children.

Monday, Johnson County public health official Dr. Elvin Adams and the Texas Department of State Health Services (DSHS) confirmed 28 mumps infections–one in Alvarado, eight in Cleburne, and 19 in Keene. The Cleburne Times-Review reported that 23 of these cases are youths ages five to 18.

Last week, Keene Independent School District Superintendent Ricky Stephens told parents to vaccinate their children in an effort to curtail the spread of the airborne virus. He said if students are under-vaccinated or unvaccinated and choose not to get immunized, they must remain at home for at least 26 days to avoid catching mumps.

Breitbart Texas spoke with Stephens. He shared  that 34 of Keene ISD’s 1,100 students were under-vaccinated or unvaccinated but half of them since chose to correct the matter and returned to school. Only 17 remain temporary homebound. Stephens said the district enacted measures so students can remain current on coursework through the end of next week–after which the district breaks for the holidays.

Texas is one of 18 states that allows families to opt-out of school immunization requirements via “reasons of conscience” and has done so since 2003. DSHS reported nearly 45,000 or 0.84 percent of the state’s 5.5 million children attending public, charter, and private schools take these non-medical exemptions.

The U.S. Centers for Disease Control and Prevention (CDC) reported mumps dropped off nationwide by 99 percent with the advent of a vaccine in 1967. Before, they estimated 186,000 cases a year. Today, the Mumps, Measles, Rubella (MMR) vaccine is said to be about 88 percent effective in reducing mumps when a child receives two doses. The CDC maintains the MMR vaccine is safe, despite unfounded claims it causes autism, as Breitbart Texas reported.

DSHS spokesman Chris Van Deusen told Breitbart Texas the department will offer two free immunization clinics–one Tuesday at Keene Elementary and the other, Wednesday, at Cleburne High, both held from 4-7 p.m. to serve other under-vaccinated or unvaccinated families and residents who would like to receive the MMR vaccine.

As of November 26, the CDC accounted for mumps outbreaks in 45 states and the District of Columbia, reporting 3,832 cases of the virus. This eclipses last year’s total of 1,088. The nation peaked at over 6,500 diagnosed mumps cases in 2006. In 2015, Texas had 20 cases of mumps. The state just reported 38 cases at the end of November.

Adams told the Cleburne Times-Review: “Mumps is highly contagious and can have serious long-term consequences for a small percentage of people who get it.”

He speculated Johnson County’s cases stemmed from a hard-hitting mumps swarm in Arkansas, where he said several Keene students visited family last month. He told the Fort Worth Star-Telegram five people returned with the virus. As of November 26, Arkansas reported 1,300 cases. Last year, they had six.

The CDC defines mumps as a viral infection that affects the salivary glands. Its hallmark swollen glands, or parotitis, causes cheeks to appear puffy. Like a cold or the flu, mumps spread through the air from an infected person’s cough, sneeze or even by talking. Children easily contract it by touching a mumps-ridden toy. While sharing cups or utensils with an infected person can spread mumps, the virus flourishes in close quarters like classrooms and dormitories.

Symptoms surface roughly 16 to 18 days after mumps exposure. Besides swollen glands, they may include fever, headache, fatigue, achiness, and loss of appetite. The CDC says mumps can be more severe for adults. Although rare, complications include meningitis, pancreatitis, and swelling of the brain, testicles, or ovaries. The virus has been linked to miscarriage in the early stages of pregnancy. Even though there is no treatment for mumps, most recover in a few weeks. Death from the virus is rare.

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