Influenza is caused by a virus, and viruses tend to be extremely resilient. They're not alive so temperature changes don't affect internal chemical reactions as it would for bacteria and humans.
Bacteria have temperatures at which they grow most effectively, which is why we try to keep food cold. Note that the food in your fridge still goes bad, and it would be pretty damn uncomfortable living at fridge temperature for humans. Bacteria are way more resilient than we are, though it varies by species.
> Influenza is caused by a virus, and viruses tend to be extremely resilient.
Viruses can be extremely resilient or extremely fragile, depending on a number of factors including whether or not they're enveloped, whether or not they're currently protected in an aerosolized droplet, etc.
