الفهرس Only 14 pages are availabe for public view
 |  | from | 155 |  |  |
| | | from | 155 | | |
Abstract
P
andemics, from the Greek pan (all) and demos (people), are caused by the emergence of novel pathogens capable of sustained person-to-person transmission through mostly susceptible populations. Pandemics thus represent widespread community outbreaks of serious human illness that affect virtually every country throughout the world. There have been a number of significant pandemics in human history, generally following the domestication of animals or other contact between animals and humans. Examples of zoonotic pandemics include smallpox, plague, tuberculosis, influenza, and more recently, HIV. Severe acute respiratory syndrome (SARS) emerged as a zoonotic infection in 2003 but did not cause a pandemic.
Influenza viruses belong to the Orthomyxoviridae family, this family is divided into four genera, influenza virus A, B, C and thogotovirus, based on antigenic differences in two of the major structural proteins of the virus, the nucleoprotein (NP) and matrix protein (M), All avian influenza viruses are classified as type A. Only influenza A and B cause major outbreaks and severe disease; influenza C is associated with common cold-like illness, principally in children.