Health is one of most important things in our life. We think that it is a real luck to have a strong health. Our way of life doesn’t increase the physiological condition of our body. Alcohol, cigarettes, unhealthy food, stresses and other factors have a great influence on our health. The human’s immune system is very uncertain thing because there is a countless quantity of different dangerous viruses and bacteria. From ancient times plague and other infectious diseases have been killing people without leaving them any chance to survive. All these diseases are even worse than wars by the quantity of deaths.