DUVALL, Wash — One out of every three families in the U.S. serves some kind of salad on Thanksgiving. However, this year, there's a serious warning about serving romaine lettuce due to an E. coli outbreak.

The Centers for Disease Control and Prevention (CDC) said the E. coli infections that have been reported across 19 states are connected to romaine lettuce from Salinas, California. 

In the northwest, lettuce season typically lasts from May or June until October, so if you are buying romaine, it's likely being shipped in, according to Jason Salvo, owner of Local Roots Farms.

Just south of Duvall, Local Roots Farm is a 15-acre diversified vegetable farm in the Snoqualmie River Valley. Salvo said their biggest crop is lettuce.

"Something like 95% of the lettuce that we eat in America in the wintertime is coming from basically two counties: one in California and one in Arizona," Salvo explained. "The farms are so big that one worker who doesn't wash his or her hands, or you know one animal gets into the field might touch one head of lettuce or a handful, but they are washed and processed together in these enormous batches and shipped all over the country. It is, in part, a problem of scale." 

RELATED: 67 people in 19 states now sickened in E.coli outbreak linked to romaine lettuce

At least two people from King County were sickened in the national outbreak. 

Separate from that, there have been six King County cases of E. coli potentially associated with four Evergreens Salad restaurants in Seattle. 

The Evergreens locations have also tossed all their romaine lettuce and extensively cleaned their cutlery and other items to cut down on any possible spread of the infection.

Evergreens released the following statement on Tuesday evening, "Food safety is our top priority. We work every day using best practices so the food in our restaurants is safe and healthy. We have been in close contact with the health department and continue to cooperate fully to learn more about the source of the issue."

The Seattle King County Health Department is working with the state Department of Agriculture and the U.S. Food and Drug Administration (FDA) to trace where that produce came from.

"People need to know if they ate at an Evergreens location and developed symptoms of E. coli, which can be diarrhea, which sometimes is bloody, nausea, abdominal cramping, that they should seek health care if their symptoms are ongoing," said King County Public Health officials.

RELATED: King County looks for source of E. coli outbreak possibly linked to Evergreens Salad chain

"A lot of it comes down to practicing good hygiene," Salvo said.

Salvo said it helps if you are able to buy local and in season.

"This is the radicchio," Salvo pointed out on his farm. "It is really nice. I would call it the local alternative to imported lettuce. We are growing it on a small scale. It is safe to eat, and it hasn't been shipped in from 1,700 miles away on a truck."