A staff member at Issaquah High School was diagnosed with the measles, the school district has confirmed.

The staff member is one of five new cases of the measles recently identified by the Washington State Department of Health. Of those five, two are residents in King County, two others reside in Pierce County and one lives in Snohomish County. In King County a woman in her 40s and another in her 50s were diagnosed.

L. Michelle, the district’s executive director of communications, did not know if the infected staff member was employed full time or part time.

Public Health of Seattle and King County advised the high school Wednesday evening that they need to verify the immunization status of all staff, the district said. In order to allow staff the needed time to obtain their records and share them with administrators, Issaquah High School will be closed Thursday, May 16.

The school is urging families to monitor their children for signs of measles. Students who may have measles are asked to stay away from school and see their primary care provider immediately. However, they should call ahead to their primary care provider before going in to prevent further spreading the virus.

A high school student at North Creek High School in Bothell was another of the group diagnosed with the measles. On top of attending school, the student had a job. Mark Beatty, health officer in Snohomish County, said the Snohomish Health District was working with the Northshore School District to gather information from the family on potential exposure sites. They’ll be available online.

Of the five, one was fully immunized, another was unimmunized and the status of the remaining three were still under investigation. Unlike the unrelated outbreak of Clark County — which occurred primarily in children — four of these second outbreak cases occurred in adults.

One has been hospitalized due to the severity of the illness.

From Jan. 1 to May 10 of this year, there have been 831 confirmed cases of measles in 23 different states, said Kathy Lofy, state health officer. This is the greatest number of cases reported in the U.S. since 1994 and the greatest number since measles was declared eliminated in 2000.

Lofy said she anticipates more cases being confirmed, due to the five subjects traveling to several different public places while infectious, and given that the measles is so contagious.

The measles virus, characterized with a red, blotchy rash, can remain in the air for about two hours after someone infected has left the area.

Issaquah High School is one potential exposure site, meaning infected individuals were at the school before a measles diagnosis was made, according to Public Health.

Anyone who was at the high school from may 6-9 from 7:30 a.m. to 6 p.m. could have been exposed to the measles.

Other Issaquah locations of potential exposure include: Coldwell Banker Bain (1151 SW Sammish Road, Suite 103), May 6 from 6 p.m. to 10 p.m., May 7 from 4 p.m. to 9 p.m., May 12, 9:30 a.m. to 1 p.m.; Hops n Drops (4506 Klahanie Dr. SE), May 9, 5:30 p.m. to 9 p.m.; Open house at Hunter’s Ridge (4548 244th Place SE), 11 a.m. to 4 p.m.

A more complete list of potential exposure sites is available on the county’s Public Health Insider blog.

The source for the infections remains unknown as Seattle and King County Public Health disease investigators and Washington State Department of Health, Tacoma-Pierce County Health Department and the Snohomish Health District search for any common connections.

A possible common exposure may have happened at SeaTac Airport. Those new cases of the measles spent time at the airport when the likely time of exposure would have happened.

“More measles in our communities means more risk of outbreaks among people who don’t have immunity,” said Jeff Duchin, health officer for Public Health – Seattle & King County, in a press release. “Measles vaccine is safe, effective and offers excellent protection. If you aren’t sure if you’re up to date with the recommended doses of measles, mumps and rubella vaccine (MMR), it’s safe to get one as a precaution.”

Lofy urged everyone to verify their immunization status, in order to ensure a high level of herd immunity, and prevent the spread of illness. “The bottom line is everybody just needs to check if their immunizations are up to date,” she said.

This story will be updated as more information is made available.