3.1.1 Communicable (Infectious) Diseases

What are pathogens?

Pathogens are microorganisms (viruses, bacteria, protists, fungi) that cause infectious disease in plants and animals.

How do viruses cause disease?

Viruses enter cells, replicate many copies of themselves, burst the cell, and release copies into the bloodstream, damaging and destroying cells which makes the individual feel ill.

How do bacteria cause disease?

Bacteria reproduce rapidly by binary fission and produce toxins that damage cells and tissues.

What are protists?

Protists are often parasitic, living in or on hosts (such as humans or animals) and causing damage.

How do fungi cause disease?

Fungi can be single-celled or have hyphae, which penetrate tissues and release spores that spread to other organisms.

What are the main ways diseases are spread?

By direct contact (touching contaminated surfaces), by water (drinking/coming into contact with dirty water), and by air (pathogens carried in droplets when sneezing/coughing).

What is an example of disease spread by droplets in the air?

Droplet infection — pathogens in droplets from sneezing, coughing, or talking are inhaled.

How can the spread of pathogens be reduced?

Improving hygiene (hand washing, disinfectants, isolating raw meat, tissues/handkerchiefs when sneezing), reducing contact with infected individuals, removing vectors with pesticides or habitat control, and vaccination (making individuals immune so they cannot pass it on).

What is binary fission?

Binary fission is the process by which bacteria divide rapidly, producing two identical cells.

What is the role of vectors in spreading disease?

Vectors, such as insects, carry pathogens between hosts. Removing them reduces disease spread.