- aren't cells
- can only reproduce inside living cells
- must infect other organisms to multiply
- can infect plant, animal and bacterial cells
- a particular type of virus will only attack specific cells
How a viruse reproduces:
- attaches itself to a specific host cell
- injects its genetic material into the cell
- uses the host cell to make the components of new viruses
- eventually causes host cell to split open
- releases new viruses
1) IN FOOD - e.g. food poisoning. You can get ill from eating food that's been contaminated with bacteria. It can be prevented by good hygiene and by making sure food is properly cooked before it's eaten.
2) IN WATER - e.g. cholera. You can get infected with cholera by drinking water that's been contaminated with sewage. It isn't a big problem in the developed world, but it kills many people in developing countries where sanitation is poor. Good sanitation can prevent cholera and other waterborne diseases.
3) BY AIRBORNE DROPLETS - e.g. influenza (flu). Flu and other viruses can be spread via the timy airborne droplets released when you cough or sneeze. Sneezing into a tissure, washing your hands properly and disinfecting contaminated surfaces can all help to prevent hte spread of flu.
4) THROUGH CONTACT - e.g. athlete's foot. The fungus which causes athlete's foot can be spread by people walking in bare feet on damp floors in places like showers and bathrooms. You can prevent it by washing your feet regularly and by not walking around bare foot. Disinfecting surfaces also helps.
High incidence of disease
A high incidence of disease is linked to poor sanitation.
The incidence of a disease is the number of new cases that occurs in a population in a certain time. - The information is likely to be given in a graph and we're asked to interpret the data.
The basic message is that poor sanitation and a lack of public health measures often contribute to a high incidence of disease.