Multnomah County says "Every year is different, four would be high for any county in the area."
According to the Centers for Disease Control and Prevention,
"A case here, some cases, some years with no cases, and now talking about 30 spread across the border and into other counties," said Dr. Jennifer Vines of the Multnomah County Health Department.
But what makes an outbreak different? Vines say because it's unexpected, unlike the flu virus.
"Flu season is a predictable spike that we get every year. We have a flu vaccine you have every year, "Vines said.
The numbers in Clark County, though, continue to rise. It's now 36 confirmed measles cases and 1
Only one case has been identified in Multnomah County. Vines says they have been preparing for an outbreak.
But why have they been preparing? Vines says it's because vaccination rates have been down.
"We've seen the number of parents delaying or denying vaccines going up in recent years, and so in addition, we have been using those tools now, "she said.
What is an outbreak? How serious is this and can we stop it?