Reasons for the increase in emerging and re-emerging viral infectious diseases

In the past two decades, humans have faced many new viral infectious agents in emerging and re-emerging infectious diseases (EIDs). Many factors contribute to the appearance of ElDs. These factors are complex but can be classified into three different categories: virus factors, human factors, and ecological factors. The factors contributing to the cause of such viral infectious diseases will be systematically reviewed in this article. (c) 2005 Elsevier SAS. All rights reserved.