Nearly 500 suspected or known cases of mumps have been identified in Northwest Arkansas as part of an "outbreak" that public health officials on Tuesday said has accelerated following a lull.
The disease, best known for causing painful and swollen salivary glands, has spread because the vaccination against it is effective in roughly 88 percent of cases, leaving more than one in 10 people who have been vaccinated vulnerable to contracting mumps, Arkansas Department of Health officials said.
Because someone who has mumps may not show symptoms or be contagious for a couple of weeks, infections often occur in waves, said Dr. Gary Wheeler, the Health Department's chief medical officer. Wheeler said he isn't sure when the disease may stop spreading in Northwest Arkansas but that he believes the current wave is peaking.
"I think we've crested, but I don't think we've seen a drop-off," Wheeler said.
Officials have redoubled response efforts, planning a second "mass vaccination clinic" for Thursday in Springdale and recommending that people in areas with a higher concentration of cases obtain a third vaccination shot, believed to further reduce someone's vulnerability to the disease.
The latest wave has sickened people in the Rogers and Bentonville school districts but is most prevalent in Springdale, Health Department public information officer Meg Mirivel said.
"We are very concerned about this outbreak," said Dr. Dirk Haselow, the state Health Department's outbreak response medical director, in a printed statement. "Mumps can have serious complications. We are seeing transmission from child to child in school settings, and we continue to see a high number of new cases."
The Health Department said Tuesday that 492 people are involved in the outbreak. Aside from confirmed cases, that number also includes people who show symptoms and can be linked to other people with the disease. It also includes people with symptoms who are awaiting either lab tests to come back or the state to establish that link.
"This is typical outbreak protocol," Mirivel said. "You don't have to confirm every single case if they've got typical symptoms and can be linked to it."
About two-thirds of Northwest Arkansas' mumps cases are school-age children, Wheeler said.
Springdale Public Schools spokesman Rick Schaeffer said as of three weeks ago, 78 students were showing mumps-like symptoms. Eight of those cases were confirmed.
"Are we still seeing some? Yes, but it's much lighter," Schaeffer said.
People with mumps are contagious for about five days after showing symptoms, so after that's when students may return to school -- whether their case is suspected or confirmed -- if they are feeling well, Mirivel said.
Schaeffer said Springdale is spraying germ disinfectant nightly throughout schools and on school buses.
Students who attend Arkansas' public schools must be vaccinated for mumps unless they obtain exemptions from the Health Department. Arkansas Code 6-18-702 allows such exemptions for medical, religious or philosophical reasons.
Wheeler said about 88 percent of people who receive two shots of the vaccine are protected from the disease. Although imperfect, the vaccine is effective, he said.
"The vaccine program seems to be working pretty well," Wheeler said. The spread of mumps "is persistent but it's moving along very slowly. It's not like polio in the '40s or measles even 50 years ago. It's relatively well-contained."
Nearly 1,900 mumps infections have been reported this year to the U.S. Centers for Disease Control and Prevention, up from 1,057 in 2015. The number of cases nationwide can vary widely from year to year. The number reached 2,600 in 2010 before dropping to 370 a year later.
When the U.S. mumps vaccination was implemented nearly 50 years ago, about 186,000 cases were being reported each year, according to the CDC.
The most common mumps symptoms are fever, headache, muscle aches, fatigue and loss of appetite, according to the CDC. The contagious disease can spread through saliva or mucus from the mouth, nose or throat, so it's spread by coughing, sneezing or talking, or sharing items like cups or eating utensils.
There is no treatment, but symptoms usually resolve themselves within a few weeks, according to the Health Department. Possible complications include deafness and encephalitis, or inflammation of the brain.
Thursday's vaccination clinic in Springdale will be from 11 a.m. to 7 p.m. at the Jones Center. Flu shots also will be made available. People may also check with their local public health unit or physicians to inquire about the mumps vaccine, the Health Department said.
State Desk on 10/12/2016