Emerging infectious diseases can be defined as infections that have either newly appeared in a population, or existed, but are rapidly increasing in incidence or geographical range. Even thought there was considerable development regarding prevention, control and elimination of some of the infectious diseases through proper use of hygiene and sanitation practices in addition to development of anti- biotics (bacteria) and vaccination, some infectious diseases remained as the leading causes of morbidity and mortality worldwide. There are many factors involved in the emergence of new infectious diseases or the re-emergence of “old” infectious diseases. Increasing global epidemiological surveillance, improving public health systems, education and research into new antibiotics and new vaccines will allow us to effectively combat the constantly renewed threat of infectious diseases. This review summarizes the work on aspects of virus emergence
