No, it's not "in the air". The elderly neighbour must have touched something contaminated by virus or been a little too close to somebody and forgotten about it. I assume she's had deliveries of some sort, even if shielding.
All viruses are quite fragile. They're not like bacteria, which can reproduce on their own, but will disappear quite quickly without a host. They have to hook up to a receptor to cause damage. They will circulate in an enclosed space for some hours, but then they disperse and become ineffective.
I doubt, too, that the 85 year old neighbour caught the virus from thin air - it is not possible.
Even catching a cold is not possible without encountering a virus somehow.
If she had not been to a test centre and had a positive Covid test it may well not be the virus so she would be at more risk going in an ambulance to a hospital where there is Covid than staying at home in the warm.
She may be getting muddled - I dud wonder if she has a UTI which could make her feel very unwell and can cause confusion in which case she needs antibiotics.
I hope someone is looking out for her.
The ambulance people will not make the decision about possible survival chances and refuse to take a patient to hospital.
There must be another reason.
Alphabetical girls and boys names January 2024
Well Labour’s “patriotism” didn’t last very long, did it? 🇬🇧