"people living in cold weather countries ie north us, canada, northern europe etc are 30% more healthy than warm climates"

This is not entirely correct according to sources I've read. Your scenario has more to do with how people live (food prep., sanitation, parasites, etc. ) than the temperature. In fact, in a pandemic situation viruses travel better through dryer air and cooler temperatures which is why we get sick in the winter with flues etc..