SEATTLE, Washington — Most measles cases in the U.S. result from international travel, according to the Centers for Disease Control. The largest measles outbreaks started with people coming into the country infected with the virus.

“We're likely to see measles continuing to enter the community, if not due to these current cases, due to future opportunities from travelers returning with measles from other parts of the U.S. or other parts of the world,” said Dr. Jeff Duchin, health officer for Public Health - Seattle & King County.

Though we can't stop the virus from being brought into the country, you can be protected if you are heading out. If you are planning on international travel this summer, health officials urge you to get a second vaccine.

“If you travel internationally you should have two [MMR vaccine] doses. If you are a student, you should have two doses. If you’re a healthcare worker, two doses. Most adults should only need one,” Dr. Duchin said.

If the measles virus is coming into the U.S. from overseas, it begs the question: Why aren’t airports, customs agents, or the TSA stopping sick people at the gate? Most of the time, measles is spread before the infected person even knows they're sick.

“They can be incubating and transmit it before they even knew they have it,” Dr. Duchin said.

RELATED: List of possible measles exposure sites in western Washington

As of May 21, there were seven confirmed cases of measles in western Washington. Those with measles often visited several public places, including Sea-Tac Airport, before going to the doctor. Sea-Tac was identified as the common measles exposure site in late April. 

Here are some tips if you plan on flying this summer:

1) Wipe down any surface thing you'll be touching regularly. Armrests, seat belt buckles, and most importantly, the tray table. Those things are disgusting.

2) Turn on the air vent over your seat. It may be annoying, but it keeps air circulating around you and may blow away any unwanted germs.

3) Ask to get on the plane first if you have kids or opt to get on last. That way you can avoid close contact with your fellow passengers

4) Choose a window seat to cut down on the exposure to passengers walking by your seat.

Isolate yourself if you think you have the measles. Symptoms typically appear seven to 21 days after exposure. 

The virus can also last up to two hours in the air, plenty of time to infect you on a plane.