**2. Types of infections**

Infectious disease is a clinically obvious disorder resulting from the presence of a pathogenic agent which can either be a virus, bacterium, fungus or parasite. These diseases are also called communicable diseases due to their ability to get transferred from one person to another (malaria, tuberculosis) and also sometimes from one species to another (flu, influenza). Infectious diseases can be vastly classified as: 1) known diseases which are insistently there (e.g., dengue, malaria, tuberculosis); 2) new, previously unknown diseases (e.g., severe acute respiratory syndrome); and 3) diseases which threaten to enhance in the near future (e.g., avian influenza). These diseases own a great risk as more than half of the deaths happening world‐ wide can be attributed to these diseases, particularly in developing countries [1]. Parasitism is based on the benefits acquired by a pathogenic bacterium invading the host and causing an infection. A bacterial infection is the process occurring when the microbe manifests its pathogenicity, and thus its capacity of inducing disease, by invading and causing a damage (locally or systemically) of the host organism. Consequently, the infectious disease could result in an acute infection, with a short and severe course, or a chronic, low-grade and long lasting infection [2].
