How many types of influenza virus are there, why we get suffer from cold mostly when season changes.

Question

There are four types of influenza viruses: A, B, C and D. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter. The emergence of a new and very different influenza A virus to infect people can cause an influenza pandemic. Influenza type C infections generally cause a mild respiratory illness and are not thought to cause epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.
People seem to come down with a cold or the flu when the seasons change. But these dramatic temperature changes aren't the direct cause of these illnesses. Rather, the temperature shifts permit a different group of viruses to flourish, and it's these viruses that make people sick.

Arpan Gandhi · Accepted Answer

There are four types of influenza viruses: A, B, C and D. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter. The emergence of a new and very different influenza A virus to infect people can cause an influenza pandemic. Influenza type C infections generally cause a mild respiratory illness and are not thought to cause epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.
People seem to come down with a cold or the flu when the seasons change. But these dramatic temperature changes aren't the direct cause of these illnesses. Rather, the temperature shifts permit a different group of viruses to flourish, and it's these viruses that make people sick.