The measles outbreak has spread to Multnomah County.

Oregon health officials tonight announced the first confirmed measles case on the Oregon side of the Columbia River in an outbreak that has led Washington's governor to declare a state of emergency.

The case in Multnomah County is the 31st confirmed measles infection since an outbreak began in Washington on Jan. 4.

The measles outbreak is believed to have started with a child who traveled overseas and spread in part thanks to low vaccination rates in Clark County, Wash., where just 85 percent of kindergarteners have been inoculated against the measles.

The Oregon Health Authority and Multnomah County health officials did not disclose the age of the Oregon resident. All but one of the previous 30 cases have been found in juveniles.

The Oregon case is linked to the Washington outbreak, county health officials said.

"Our case had contact with a known case in the Washington outbreak," says Dr. Jennifer Vines, deputy health officer for the Multnomah County Health Department. "We are working to contact anyone who may have had contact so we can contain the spread here on our side of the border."

Vines says it's unclear how many people have been exposed, or where. Tonight's release suggested the exposure sites were in Wood Village and Troutdale.

"We're early in this right now," Vines says, "so I don't have numbers."