Dr. Gary Goldbaum of the Snohomish Health District says one child was hospitalized for several days but has since been discharged.
All four people reported vomiting and diarrhea.
The exact type of E. coli has not yet been identified.
The Daily Herald says the animal farm is run by Everett's parks department and has 25,000 visitors a year. Animals include sheep, calves, piglets, chickens, goats, ducks, a horse, a pony and rabbits.
Everett spokeswoman Kate Reardon says the city spent more than three hours thoroughly cleaning the farm after learning of the E. coli cases.
She and Goldbaum say they feel it's safe for children to visit the farm, but emphasize the importance of vigorous hand washing after contact with farm animals. Source