Microorganisms called pathogens are not limited to viruses. Tuberculosis, cholera, plague, dysentery, syphilis and tetanus are all infections caused by microorganisms. Rickettsia and Chlamydia bacteria are also known as pathogens causing infectious diseases.
These Contagious Diseases have had a profound impact on the history of mankind. The plague epidemic called "black death" responding across Europe in the middle of the 14th century. We know the epidemic was caused by fleas carrying the plague. About a third of Europe's 100 million inhabitants lost their lives during that catastrophe.
Symptoms of deadly virus infection vary. Bubble plague causes great fever and swelling of the lymph nodes, pulmonary plague causes pneumonia, etc.
In the mid-19th century bubonic plague caused the death of about 12 million people in China and India.
We could believe it's a disease that's past, but it's not completely eradicated, as the death of 50 people in 1994. In fact, there are a few countries in Africa and South America that the World Health Organization has designated as polluted regions of plague.
Napoleon, in full Europe's conquest campaign has been forced to withdraw not only from climatic conditions from Russia, but also because of the typhoid fever among its people.
Variola and other infectious diseases have caused epidemics that have ravaged American continents as a result of first contact with Europeans.
Recently, anthropologists have concluded that between 85 and 90 percent of the indigenous population of the two Americas have been liquidated by microorganisms made by Europeans, this is the most important Factor in conquering the native civilizations. Americans speak Spanish, Portuguese, French and English today, because of microbes.
There are countless such cases where contagious diseases have changed the course of history. Method of vaccination against smallpox discovered by english physician Edward Jenner has become popular all over the world and the number of people affected today it gradually dropped, because at the end of the Second World War there are almost no cases of illnesses.
The last case was diagnosed in Somalia in 1977. Here's why it is said that smallpox is the only contagious disease ,the eradication of which he succeeded.
The disease of contagious disease caused by the specific virus,was once a widespread disease among children. Babies and surviving children have acquired immunity and have not contracted the disease for the rest of their lives. Adults who did not have measles in their childhood, died in measles epidemics that had repeatedly erupted in the world.