#**causes of disease**

##**pathogens**

*1)what they are,2) how they get into the body & 3) how they cause disease*

**1) pathogen:** any micro-organism that causes disease. (*pathogens include bacteria, viruses & fungi)*
**2) gas exchange system:** many pathogens enter the body through the gas exchange surfaces. pathogens that cause influenza, tuberculosis & bronchitis infect in this way.
**2) digestive system:** food & water may carry pathogens into the stomach & intestines via the mouth. cholera, typhoid & dysentery pathogens enter by this means.
**3) By damaging host tissue:** numbers can cause damage, some break down the membranes, viruses can take over the DNA and RNA of hosts.
**3) by producing toxins:** pathogens can produce toxins. cholera can produce toxins that lead to excessive water loss from the lining of the intestines.

##**lifestyle & health**
1) risk, 2) lifestyle choice and cancer, 3) lifestyle choice and coronary heart disease, 4) reducing risk of cancer and CHD