Officials in Livingston County confirmed another mumps case on Wednesday, bringing this year’s total to three.
Kathy Root, the county health department’s director of patient services, said the person with the newly confirmed case is a student in the Livonia Central School District who had contact with the two people infected earlier this year.
The school district did not immediately respond to a request for comment.
All three people infected with mumps are fully vaccinated against the disease, Root said.
It’s an outcome that’s statistically unlikely but still possible, she told WXXI News earlier this month when the second case was reported.
“No vaccine is 100 percent effective,” said Root. “But we have to keep vaccination levels high if we want to prevent further spread.”
People who are fully vaccinated are about nine times less likely to get mumps than if they're unvaccinated, but close and prolonged contact with someone who has mumps increases the odds of contracting the disease, according to the federal Centers for Disease Control and Prevention.
Livingston County had no cases of mumps last year, but there is an ongoing rise in the number of cases nationally amid declining vaccination rates in some communities, the CDC says.
There were two cases of mumps in Monroe County and none in the five surrounding counties in 2017, the last year for which statewide data is available.
