How does H1N1 virus jump from animals to humans?
Usually the H protein on a pig or bird virus doesn’t fit easily into the receptor of a human cell. So a person exposed to such a virus is unlikely to get infected. However, random changes may occur in the genes that control the shape of the H protein and allow the virus to pass through the cell wall. This gives rise to a new strain of H1N1 that’s adapted to humans. Now the virus can pass from person to person, as is happening now. Contact with infected pigs or birds no longer is necessary.
