PORTLAND, Ore. — The measles virus has spread to dozens of people in Clark County, Wash. during the past few weeks. Several others have been identified as suspected cases of the measles.

We've explained several basic facts of the virus and why it's important to get vaccinated, but we wanted to dive into a few more questions we've gotten since the virus has spread.

What is herd immunity?

Herd immunity is what happens when a community has an immunization rate of 90 percent or more. Because so much of the population is immunized, the people who cannot be immunized - like children who are too young and people with compromised immune systems - will be protected.

Clark County hasn't had "herd immunity" since 2004-2005; according to 2017-2018 rates, 23.5 percent of the county was not immunized. 

A higher rate of un-vaccinated individuals puts the rest of the community with compromised immune systems at risk. 

What does a public health emergency mean?

Clark County Council voted to classify the measles outbreak in the area a local "public health emergency," and Washington Gov. Jay Inslee made a similar declaration.

Both declarations basically mean the county will have extra support from outside of their jurisdiction in battling this measles outbreak. 

The local declaration meant Clark County was able to speed up the process of getting nurses and epidemiologists from outside the area to come in and conduct disease investigations. 

Gov. Inslee's declaration allows state agencies and departments to do "everything reasonably possible" to help Clark County battle the outbreak.It also allows the Washington the ability to request extra resources from out-of-state.

The Washington State Department of Health has created an infectious disease unit to manage investigations, lab testing and efforts to protect communities.

The Washington Military Department is helping local officials relieve impacts to people, property and infrastructure. 

How do I know if I got the vaccine?

Without your childhood immunization form, it's hard to know whether or not you got the measles vaccine when you were younger.

The Centers for Disease Control say if you were born before 1957, there's no need for you to get the vaccine. 

If you were born between 1957 and 1967, you should get re-vaccinated, because you may have received a killed virus version of the vaccine. 

If you were born after 1967, you should be covered.

If you're still not sure whether or not you got the vaccine, you can go to a clinic and get tested.

Eileen Morton, a manager at Any Lab Test Now in Vancouver, said they’ve seen a big increase in people coming to get their immunity for the measles tested since the outbreak began.

She said it’s mainly people who work with kids who need to show their vaccination records but don’t have access to them.

“People who are 30, 40, 50 years old. At 40, it's kind of tough to go to your mom and say, can I have my immunization records? Mom's going to look and say, [the records are] long gone. So the easiest way is to come in and have a simple blood draw,” said Morton.

The lab can test you and have the results the next day, and you can even get your vaccine on site if you need it.