If it truly is an "alert" message from the Snohomish County Health Department, then why not just leave the alert message instead of having the caller call back and punch in their phone number? Sounds phony to me. Probably a debt collector posing (shouldl be illegal) as the health department to see if the number they are calling to contact whoever it is they are trying to call to see if the number is a good one.
Debt collection agencies refused to understand that the phone company recycles phone numbers and whoever had the number before IS NOT THE PERSON THEY ARE LOOKING FOR...!!! Get a clue, debt collection agencies - use a different means to track down the debtor you are trying to find...!