The Snohomish County Violent Offender Task Force tracked him down at his former employer's business, sheriff's office spokeswoman Shari Ireton said.
The suspect, 40, once lived with the girl's mom in an Everett apartment.
Both the mother and daughter were diagnosed with a form of herpes almost exclusively contracted by sexual contact.
Prosecutors last week filed a child molestation charge against the man. The Herald is not naming him to protect the privacy of the victim.
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