What are infectious diseases?
Infectious diseases are diseases which can be passes from one person to another.
They come in two main forms:
Small, single cellular organisms. They are much smaller than the animal and plant cells, however, have many similar structures. Bacteria reprouduce by splitting into two. They also can produce toxins.
A virus is many more times smaller than a bacteria. They will get inside body cells, reproduce and burst out, killing the cell. Viruses will not reproduce on their own, they wait for the host body cell to reproduce.
Artificial defence against disease
Ignaz Semmelweis was a doctor who first came up with the idea of infectious diseases being spread easily. In the hospital he worked in, he was able to observe medical students performing dissections, then delivering babies. Many women died from diseases. Semmelweis believed these were passed on by the doctors unwashed hands. Upon telling the doctors to wash their hands, death rates fell.