| The Biology of Influenza and Vaccination 10 hours ago by Jesse Seasonal influenza viruses are type B viruses; they only infect humans and usually cause mild disease in young healthy people. … H1N1 is a type A virus, which can infect other animals, such as pigs and birds, as well as humans…. There are also at least 100 different ‘common cold’ viruses that can ca ... H1N1INFLUENZAVIRUS.US - h1n1influenzavirus.us · Rank: 73,352 |