Table 1.

Selected major and contributing factors to the prevalence of emerging and re-emerging infectious diseases [Adopted from Church (7)].

Major factors	Contributing factors
Global changes in population demographics and distribution	Population growth and density, migration to urban areas, increased widespread travel, immigration, and housing practices
Change in human behaviors	Food distribution and transportation services, liberation of sexual practices, increased need for childcare outside the home, alcohol and drug abuse, change in immunization practices
Changes in environment and land usage	Global climate changes such as increase in average temperature, deforestation, change in land usage, and natural disasters (Floods, intense droughts, catastrophic storms)
Chronic manifestations of infectious diseases	Modern medical technology in developed countries prolongs the life of people with life-threatening chronic diseases
Advanced pathogen detection	Advanced molecular methods have been developed for the detection of fastidious, uncultivable organisms
Microbial evolution	Adaptation of microorganisms to the environment in order to survive
Collapse of public health systems and bioterrorism	Decreased funding of the public health systems, insufficient public health infrastructure, mobility of population, increased international travel, immigration and refugees, wars, conflicts, bioterrorism