COVID notification from a state I wasn't in... or was I?

December 29, 2021 2:27 PM

I am currently in Massachusetts. This morning I made MassNotify active on my phone. Within hours I had a MassNotify exposure notification, saying that I had been exposed nine days ago. But I wasn't in Massachusetts nine days ago. What gives?

Nine days ago I was at work in Washington State. I had WA Notify on, and definitely could have been exposed --- but the notification on my phone is adamantly from Massachusetts. I had probably already given MassNotify permission to keep an eye on me, but it wasn't the active one on my phone. Any thoughts on what's going on?

(I know the notification system is flawed and almost useless. I will be getting a COVID test at the next opportunity. I do not have symptoms. This is my fifth notification and I might as well collect them like really lousy geocaches.)

posted by The corpse in the library to Computers & Internet (3 answers total)

The most likely situation is that that you were near somebody nine days ago (for more than X minutes where X is probably 15 minutes, but is whatever threshold was set by MassNotify, nearness very roughly estimated by bluetooth signal strength) who has since tested positive for Covid-19, has Massachusetts as their active region and reported their positive test to Massachusetts. Presumably they were traveling from Massachusetts to Washington and didn't switch their region. When you switched your phone to the Massachusetts region your phone found one of it's transmitted random id's on the the "notify these phones" list it downloaded from the Massachusetts region. Details on how Exposure Notifications work can be found at Apple / Google's Privacy-Preserving Contact Tracing site.
posted by RichardP at 2:55 PM on December 29, 2021

Best answer: From the MassNotify webiste:

Does MassNotify work if I travel out of state?
MassNotify is compatible with exposure notification services in other US states and will send you exposure notifications while you are in another state without issue.

Now, that's somewhat ambiguous, but the app is certainly intended to work across state lines - this article from when the Apple/Google app was first coming into use last year says, "If someone with Wyoming’s app tests positive, their keys are uploaded to a server and can be accessed by devices using apps from Delaware, New Jersey, New York, North Carolina, North Dakota, Pennsylvania, and parts of California that are participating in a pilot program."

On the other hand, I currently have a MassNotify exposure notification on my phone for a day when I only left the house (which I live in alone) to take a solitary walk in the woods, so who knows?
posted by mskyle at 4:26 PM on December 29, 2021 [1 favorite]

Response by poster: Ah, I missed that they worked with other states (as they should). Thanks!
posted by The corpse in the library at 6:15 PM on December 29, 2021