What is the causative organism of Swine Flu?

Answer 1

Viruses. Flu of any type is caused by influenza viruses. In Swine Flu the specific microbe is the Influenza Type A, H1N1/09 virus.

Additional Note:

Viruses are sometimes classified as microbes. However, not all scientists classify a virus as a "microbe". Most of them do for lack of a better way to talk about them instead of "germ" or other less specific nomenclature. Unlike the other microbes, they are not living organisms. Viruses are specialized groups of "cells" that perform functions working in an organized way. They latch on to and break into a living host's cells and use the life, energy, and nutrients from the host in an almost parasitic way. The genetic material that they have inside themselves combines with that of the host's cells to cause the host cells to stop reproducing more cells like itself for the host and start making viruses like the one that invaded it instead.

See the related questions below about what caused the 2009 swine flu and what are the different types of microbes.
an isotype of the influenza virus

Answer 2

people, maybe some animals.