For bacteria and viruses to cause disease they must first colonise the patient.
Once they have invaded the host they can multiply readily.
If the host is immune to the virus or bacteria due to previous exposure or vaccination, these organisms may not be able to cause disease.
How do bacteria cause disease?
Bacteria cause disease by secreting or excreting toxins (as in botulism), by producing toxins internally, which are released when the bacteria disintegrate (as in typhoid), or by inducing sensitivity to their antigenic properties (as in tuberculosis).
What are the main characteristics of a bacteria?
Bacteria are like eukaryotic cells in that they have cytoplasm, ribosomes, and a plasma membrane. Features that distinguish a bacterial cell from a eukaryotic cell include the circular DNA of the nucleoid, the lack of membrane-bound organelles, the cell wall of peptidoglycan, and flagella.
How can bacteria be harmful to humans?
There are two ways bacteria can harm the human body: toxicity – the bacteria produce toxins which damage specific tissues in the body. invasiveness – the bacteria multiply rapidly at the site of infection and overwhelm the body’s defence mechanisms. The bacteria may then spread to other parts of the body.
How can the spread of bacterial diseases be prevented?
Keep the germs away:Wash your hands before eating, or touching your eyes, nose or mouth. Wash your hands after touching anyone who is sneezing, coughing or blowing their nose. Don’t share things like towels, lipstick, toys, or anything else that might be contaminated with respiratory germs.