Biological Agents As Causes Of Disease

Question 1

Pathogen

Answer 1

• Microorganism that causes disease
• Infectious viruses, bacteria, protozoans or fungi
  
  • Many scientists would also incl. worms and prions
• 1/3 of all human deaths are caused by pathogens
• The average human contains 10^13 human cells and 10^4 microbial cells. These flora are usually distinct from pathogens

Question 2

Types Of Pathogen

Answer 2

• Obligate pathogens- can only survive inhost
  
  • usually v. specific to host species
• Facultative pathogens - present in environment (reservoir) waiting for host
• Opportunistic pathogen - normally benign but cause a disease in compromised host