Diseases and the Immune System

What is a disease?
A disease is an illness or sickness caused by a virus, bacteria or parasite that presents with certain symptoms and physical signs. There are many diseases that are present in our modern day world and each of these presents with specific symptoms and physical signs, which allow doctors to make a diagnosis and treat the illness.
Diseases include such things as measles, mumps, chicken pox, cholera, dysentery, hepatitis A and poliomyelitis. Many of these diseases can be dealt with by our bodies own defence system, but sometimes the body needs help as it is unable to combat the disease and this is when doctors prescribe antibiotics and other medications
How bacteria and viruses enter the human body.
There are a number of ways in which diseases enter the human body. Bacteria and viruses can be airborne(droplet) and enter the body through our respiratory system eg the flu or the common cold is often spread when by someone sneezing. Some of the virus is released into the air in droplet form and is then taken in by the respiratory system of other people in close contact.
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