Summary
The CDC identified rare mutations in the bird flu virus from the first severe U.S. human case, found in a Louisiana resident over 65 with severe respiratory illness.
The mutations, located in the hemagglutinin (HA) gene responsible for cell attachment, differ from those in local backyard flock samples and align with severe cases seen abroad.
The patient was infected with the D1.1 genotype, recently found in U.S. wild birds and poultry, not the B3.13 genotype seen in humans and livestock elsewhere.
The CDC states no person-to-person transmission occurred, and public risk remains low.
In my experience it’s a smell or, now, a particulate test read by a computer.
A smell that can’t breech the N95 and does not linger is sprayed. If you can smell it there’s no tight seal and you fail the fit. Now, it’s often read by computer, because some individuals can’t smell the subtle aromas in the solutions used, more so post COVID. A tube is riveted to the front of the mask while particulate is aerosolized while a computer reads the interior environment of the mask to see if there’s a breach on the seal, and if there is, you fail the fit.
I’ve never encountered “fit” for items that don’t require an airborne seal. There’s training on how to don and doff the gear, often in the form of computer based modules instead of in person, but no “fit”. Or it’s offered and I can decline because once you know you know, for the same gear.
I can only speak to medical and psych facilities, clinics, contexts in the United States.
I did Google it. What I find in a 100mile radius is “online” fit testing certifications for $35-50. Save your money, a particulate breech test in person is required. I’m guessing you got lucky there, by your location.