Infectious diseases represent big public health issues due to their ability to spread very fast and easy. Sources of infection are infected people and animals. Causes of infection are various types of microorganisms: viruses, bacteria, fungi, parasites. Infectious diseases can affect different organ systems, depending on their causes and ways of transmission. When it comes to respiratory infections, the cause is transmitted through air, which makes it easier for it to spread. Viruses are most common causes of respiratory infections, but they can also be caused by bacteria, mycoplasma and chlamydia. Pertussis is highly contagious acute respiratory infection and it usually affects children up to 7 years old. It is caused by bacteria Bordetella pertussis. Typical cases include so-called whooping cough, followed by strong inhalation of breath, coughing out sticky mucus and sometimes vomitting. Vaccination is the best way of prevention and it is implemented through three doses of combined Di-Te-Per vaccine in the first three years of life, and giving booster doses later in life. Vaccination against pertussis in Croatia first started in 1959 and since then the number of infected people was reduced drastically. Incidence rate of pertussis in Zagreb for given period of observation (2010-2014) was at its highest in 2014, when it was 6,58/100 000. Percentage of infected males for given period of observation was a little higher than those of females (54,74%). Compared to other Croatian counties and Croatia in general, Zagreb had somewhat higher incidence rates of infected people. However, when compared to Europe, both Zagreb and Croatia had lower incidence rates of infected people. It is very important to notice the symptoms of disease in its early stage so the treatment can start immediately which will lead to milder symptoms in later stages of disease.