Officials have identified 28 cases of mumps in Johnson County, mostly in school-age children in Cleburne and Keene, said Dr. Elvin Adams.
The state hasn’t had more than 20 cases of the virus since 2011.
“It’s really unusual,” said Adams, who works with the Texas Department of State Health Services. “We’re having more than a year’s worth of cases in one community.”
Of the 28 cases, 19 are in Keene, eight in Cleburne and one in Alvarado. Children and youths ages 5 to 18 account for 23 of the cases, Adams said.
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Adams said the virus is believed to have come from an outbreak in Arkansas, where several students from Keene had visited family about a month ago. Five people returned home with the virus, he said.
The Cleburne and Keene school districts began taking precautions to prevent an outbreak last week, identifying students who might have come in contact with the virus.
Students who do not have the mumps vaccine must either get immunized or stay home for 26 days, Adams said.
Ricky Stephens, the Keene superintendent, told WFAA last week that 34 of the district’s 1,100 students aren’t vaccinated. Statistics for the Cleburne school district were not available Monday.
There is no treatment for mumps. Adams said the virus often leads to facial swelling, after which patients are often clear of the virus in about five days.
Other effects can include brain infection, swelling of salivary glands and pancreas — leading to pancreatitis — and swelling of the testicles and ovaries.
Infected males could become sterile, though long-term-complication rates are low, Adams said.
Mumps cases have declined drastically since the 1960s, when widespread vaccinations began. Before that, about 180,000 cases of mumps a year were reported in the United States, according to Centers for Disease Control and Prevention data.
Since the 1960s, the numbers have fallen by about 99 percent, now ranging from 1,000 to 2,000 cases a year.
Still, outbreaks have happened. The MMR vaccine for mumps is about 88 percent effective when a child gets two doses, according to the CDC.
“The vaccine can’t ever be perfect,” said Dr. Suzanne Whitworth, medical director of infectious diseases at Cook Children’s Medical Center in Fort Worth. “We know these viruses circulate, and for whatever reason, it will just take off. Mumps is really contagious.”
This year, nearly 2,879 cases nationwide had been diagnosed as of Nov. 5, already the most since 2006, when more than 6,000 people were diagnosed.
In Texas, about 38 cases a year were diagnosed from 2005 to 2015, peaking at 121 in 2010, according to Department of State Health Services data.