Seasonal (or common) flu is a respiratory illness that can be transmitted person to person. Most people have some immunity, and a vaccine is available.
Avian (or bird)
flu
is caused by influenza viruses that occur naturally among wild birds.
The H5N1
variant is deadly to domestic fowl and can be transmitted from birds to
humans.
There is no human immunity and no vaccine is available.
Swine
(or pig) flu is a respiratory disease of pigs caused by type A
Influenza that regularly causes outbreaks in pigs, usually in the late
fall and winter months, similar to seasonal influenza in humans.
At this time, there are four variants of swine flu H1N1, H1N2, H3N2 and
H3N1. Most recently, the H1N1 viruses have been isolated. Swine flu
does not normally infect humans, however sporadic human infections have
occurred. The symptoms of swine flu in humans is similar to human
seasonal flu, including fever, lethargy, lack of appetite and coughing.
Some people with swine flu also have reported runny nose, sore throat,
nausea, vomiting and diarrhea.
Pandemic flu is
virulent human flu that causes a global outbreak, or pandemic, of
serious
illness. Because there is little natural immunity, the disease can
spread
easily from person to person. Currently, there is no pandemic flu.