Will avian flu fully jump the species barrier from poultry to people?©GAIL EISNITZ

More and more animal diseases are "jumping" the species barrier to infect human beings, and the avian influenza strain H5N1 is no exception (see "Connecting the Dots," cover story, November/December 2004). According to the World Health Organization (WHO), since 2003, 170 people have contracted avian influenza H5N1, 90 of whom have died. Most of the human cases have occurred in Asia, and in places where people have direct contact with diseased poultry—either on farms or during preparation of the meat.The WHO has documented that the H5N1 virus spread to 13 new countries last February. Azerbaijan, Bulgaria, Greece, Italy, Slovenia, Austria, Iran, Germany, France and Hungary have all found the virus in wild birds. Egypt, India and Nigeria have discovered infected domestic poultry.

The virus does not currently have the ability to spread between humans, but according to the WHO, "The risk of pandemic influenza is serious
The number of deaths caused by a pandemic virus vary greatly, and cannot be known prior to the emergence of the virus. During past pandemics, attack rates reached 25 to 35 percent of the total population." The more the virus spreads across the world, the greater the chances a pandemic can occur.