Ch 8.2 sources of infection

Viruses Viruses are not living things, they are ‘protein fragments/crystals’ that cause colds, flu, mumps, measles, rubella, warts, chicken pox, cold sores (herpes) and polio and many others.  they are similar to the material in the nucleus of a cell  They tend to mutate (change shape) regularly – hard to define  are only ‘nearly’ alive when they penetrate and take-over the nucleus of the host cell.  They direct the cell to make millions more copies of the virus,  the cell then bursts and releases more of the virus.  As they are not living, antibiotics (anti-living) drugs don’t work, all we can do is treat the symptoms, usually with Panadol, fluids and rest.

Childhood diseases New borns tend to catch many colds and diseases until they develop the antibodies to fight off pathogens. These types of diseases had disastrous effects on indigenous populations (with no natural or developed immunity) during the Western exploration of the planet.  Measles – a viral infection with flu like symptoms, a red rash but with some possible severe side- effects.  Chickenpox – flu like symptoms and the virus can remain dormant in the nerves for up to 40 yrs and reappear as shingles.

Parasitic Disease A parasite is an organism that lives on or in the body of a host and causes damage to the host eg stomach worms and ticks.  Malaria – infection caused by a unicellular parasite – plasmodium.  Amoebic dysentery is caused by drinking dirty water containing a single celled organism (usually a cyst containing the parasite). Causes severe vomiting and diarrhea – was common among Australian prisoners during WW2 in the Pacific, and is still prevalent in developing countries with inadequate water treatment.

Fungi Fungi include mushrooms, are ‘plant-like’ but cannot perform photosynthesis, therefore they live off a host. They disperse spores (similar to seeds). Fungal infections are contagious; examples include - Tinea and Thrush. Treated with fungicides.