I will try to answer your question again.
In the case of a pandemic, even part-time firefighters will be called in. These people will be called upon by their communities to help out. These people will answer the calls for help that they receive.
It is impossible for me to distinguish between the work of a part-time firefighter and the work of a professional full-time firefighter. We cannot make that distinction. When they are facing a virus, they are just as vulnerable as anyone else. That is impossible for me to do.
What happened to people working part-time during the last pandemic? Unfortunately, I cannot say. I do not have that information. I can only speak for the firefighters I was working with at the time.