In the annals of human history, avian influenza is not new. More than 50 million people died from a strain that tore through war-torn nations in 1918, more than from any other known disease outbreak. Although human infection with this type of bird flu has been extremely rare thus far, the highly virulent variant known as H5N1 is currently responsible for a worldwide animal pandemic.
The strain has killed millions of birds in the wild, caused the deaths of billions of poultry birds, and infected at least 48 species of mammals since it first surfaced in 1996. Farm cats who drank unpasteurized milk from H5N1-infected cattle have passed away in the US.
The most recent strain is not easily transmissible among humans. The virus has claimed 463 lives since 2003 and has a terrifying over 50% death rate in humans. Human-to-human transfer incidents are believed to have been few and not very persistent thus far.
