Are swine flu or bird flu viruses dangerous?
When swine flu or bird flu viruses develop the ability to spread from human to human, they can be very dangerous: they can cause a pandemic, and they can produce severe disease. One reason that pandemic illness often is more severe than the regular winter flu is that the virus is so new. The regular winter flu viruses that circulate each year are human influenza viruses and are similar to the viruses that have caused the flu in years past. As a result, most people have some degree of immunity to the latest regular human flu virus. The unusual swine flu or bird flu viruses that develop the ability for person-to-person spread are so different from regular human flu viruses that many people have little or no immunity to them. That is what experts think has happened with the new swine flu H1N1 virus. Q: How contagious will this virus be? A: So far, this virus appears to be somewhat more contagious than the usual seasonal human flu virus. About a quarter of people who have had close exposur
