In a changing world, changing disease and their agents, and the WHO in 2006 by a new definition of infectious diseases.

New infectious diseases are caused by pathogenic factors still exist parasites who Evolving acquired new properties. Infectious diseases change phenomenon is not new, but over the last 50 years, new diseases discovered very much. An increase of 4 times, especially during the last 25 years. Has changed not only the agents, but also vectors (eg .: ticks, mosquitoes). Today the most common and major socio-economic losses resulting in new infectious diseases are as follows: Chikungunya, Ebola fever, avian and swine flu, HIV, West Nile fever and others.

One of the most effective forms of prevention is immunization. Other effective means of environmental sanitation improvement, water and food quality supervision and control of the population hygienic habits, education, healthy workplace. All of them have helped reduce the incidence of infectious diseases in developed countries. However, micro-world provides daily surprises, so we have to put the effort in order to prevent the spread of communicable diseases.