It is caused by a virus .The most common subtype,or strain ,is influenza type A H1N1.This subtype has also caused infection in humans however this H1N1 swine flu virus is different from the human virus .
It is spread from the infected pigs mainly .It spreads from person to person when the virus enters the body through eyes, nose and mouth during coughing and sneezing.
Symptoms
The symptoms in humans are very similar to those of seasonal influenza .people with swine flu may experiance dry cough, fever ,headache , nasal congestion, sore throat,muslepain, neusea, vomiting, loss of appetite, tiredness, lack of energy etc.