Cardboard box's confusion?

I am only guessing but maybe cardboard would absorb moisture from the virus and kill it whereas plastic would not.

There is a scientific article about it on line, plus other surfaces.

Can’t remember but googling it will bring it up

We're lucky enough to be able to have a bonfire on our field. Up until now we've been burning the cardboard boxes from Amazon and other deliveries. We unpack them outside wearing gloves.

That site was where I found that heat above 53c kills it, so I heat up my newspaper in the oven , just like another gran and it seems to work ok