(WBIR-Knoxville) The number of measles cases in the U.S. has reached a 20-year high.
According to the Centers for Disease Control and Prevention (CDC), 288 people have been infected with the disease since the beginning of the year.
Measles is a highly contagious respiratory disease caused by a virus.
Most of the reported cases are in Ohio, but Tennessee is one of the 18 states affected. There are at least five reported cases in the state but none in Knox County.
Knox County Health Department Director Dr. Martha Buchanan said Knox County has not seen a case of the measles in at least 10 years.
"I've never even seen a case of the measles so one of the challenges is doctors aren't thinking measles," Dr. Buchanan said.
While Knox County, Tenn. has zero reported cases, Knox County, Ohio has the most at 138 cases. USA Today reports the actual count is 166 as of Thursday.
Those cases come from the Amish community, where vaccination rates are low. Amish missionaries brought the virus back from the Philippines.
"These cases of the measles have been imported into the United States from other countries where they have ongoing outbreaks. And then people here in the United States, who are not vaccinated or not completely vaccinated, get exposed and come down with a disease," Dr. Buchanan said.
While there have only been 288 cases of the measles in the U.S. this year, Dr. Buchanan said an outbreak is considered "three linked or connected cases in an ongoing transmission."
According to the CDC, out of all the reported cases in the U.S., 90% of the people infected had not been vaccinated or did not know their vaccination status.
"People's reasons not to vaccinate their kids are extremely personal and vary greatly. Certainly there are religious exemptions, there are concerns people have about what vaccines can do for their children," said Dr. Buchanan.
Measles is one of the live vaccines given.
Even though vaccination can be a controversial topic, Dr. Buchanan said Knox County's vaccination rates continue to reach the 90 percentile.
The measles do remain officially "eliminated" in the U.S. However, the CDC and the Knox County Health Department encourage people to be up-to-date with their vaccinations.