More than 800 students in the Washington county that is battling one of the nation’s largest measles outbreaks have been ordered to stay away from classrooms for up to three weeks, The Seattle Times reported Wednesday.

Students deemed to have been exposed to the measles have been told to stay away from schools, the paper reported. According to the Times, if one student is diagnosed with measles, all classmates are considered exposed. All parents who cannot provide vaccination information for their child have been ordered to keep their child out of school, the newspaper noted.

Students in Clark County, Wash., have missed field trips, after-school activities and an assembly honoring Martin Luther King Jr. since the outbreak began spreading in early January.

There have been 70 confirmed cases of measles in Clark County as of Thursday. Sixty-six of the cases occurred in people 18 or younger and the vast majority were among those who have not been vaccinated against the highly contagious disease. 

{mosads}More than a dozen Clark County schools, predominately in Vancouver, had students stay away from school. Students are supposed to be kept out of class for 21 days after the day of exposure, but the newspaper noted that administrators don’t often know about exposure until days or weeks after.

“School exclusions are a critical tool and public health strategy to control outbreaks of disease in school settings,” state health department epidemiologist Dr. Scott Lindquist said in a statement. “We have to be aggressive in identifying cases, isolating them and reducing public exposure to slow the spread and protect Washington residents.”

Most are doing homework on handouts or using school-issued laptops at home to stay on top of their school work, the Times reported.

“The impact of children being excluded from schools goes beyond just the kids missing classroom time,” a Clark County Public Health spokeswoman said in an email to the newspaper. “It also affects parents who may have to take time off of work to stay home with kids. We, as a department, recognize that impact.”

Public health officials have blamed the ongoing measles outbreak on vaccine skepticism and misinformation being spread online. A long-term study published on Monday again found no link between autism and the vaccine against measles.

Clark County, which is just across the Columbia River from Portland, Ore., has been dubbed a “hot spot” for outbreaks because of the high rate of students with nonmedical vaccine exemptions, The Washington Post reported last month.

Roughly 7 percent of students in Clark County were exempt from compulsory vaccines upon entering kindergarten by claiming personal or religious reasons in the 2017-2018 school year, according to state data.

Roughly 2 percent of children enrolled in kindergarten across the country forego required immunizations for nonmedical reasons.

Washington is one of 17 states that currently allow “philosophical-belief” vaccine exemptions because of personal, moral or other beliefs, according to the National Conference of State Legislatures. 

The Washington state House, however, on Tuesday passed a bill eliminating personal or philosophical exemptions for the measles, mumps and rubella vaccine for school-aged children.

The bill will now head to the state Senate, which is expected to vote on a broader measure related to vaccines in the next week. 

The state of Washington has reportedly spent at least $1 million so far combatting the outbreak, according to The Seattle Times.