Novel and re-emerging respiratory infections.

Over the last decade a number of novel viral respiratory pathogens have appeared or been recognized. Most of these are zoonoses, which have the capacity to infect humans directly or via an intermediate host. All but metapneumovirus are known to have caused epidemics of severe disease and at least two (the severe acute respiratory syndrome-coronavirus and influenza H5N1) have the potential to cause global pandemics. Possible preventive measures and treatment options against these new diseases are discussed in this review.