Viruses and Parasites and Human Disease

Question 1

What is a virus?

Answer 1

- infects:
   \+ humans
   \+ animals
   \+ plants
   \+ bacteria
   \+ fungi 
   \+ algae
   \+ protozoa
- viruses are very small

Question 2

Characteristics of viruses (basic rules)

Answer 2

Rule 1: they all have a nucleocapsid
Rule 2: the viral genome is RNA or DNA
Rule 3: the nucleocapsid is either
- icosahedral (spherical in appearance) OR
- helical (rod shaped in appearance)
Rule 4: they are either enveloped or unenveloped viruses

Question 3

Virus classification

Answer 3

• genome: DNA or RNA
• capsid shape icosahedral or helical
• envelope or unenvelope
• genome architecture

Question 4

Mode of transmission

Answer 4

• direct physical contact
• indirect contact
• common vehicle
• airborne
• arthropod borne
• latrogenic
• nosocomial
• zootonic
• vertical

Question 5

Portals of entry

Answer 5

• mouth
• eyes
• foetus
• vagina
• rectum
• skin

Question 6

Tropism

Answer 6

• the capacity of a virus to infect and damage specific
  cells or tissues
• associated with cell surface attachment
  + viral proteins and cell surface receptors
• there is a virus for every tissue and cell type in our
  bodies

Question 7

Different types of infection

Answer 7

• acute: influenza
• latent: varicella - Zoster virus
• progressive: HIV
• chronic/persistent: Hepatitis C
• transformative: human papillomavirus

Question 8

Different types of Parasites

Answer 8

• not intracellular - live outside the host
• most cause disease, although some can be commensal
• gain nutrients from the host
• enormous variability: single cell protozoa to complex
  worms

Question 9

Protozoa

Answer 9

• single-celled organisms
• parasites of the gut: transmission via faecal-oral route
• parasites of the blood: transmission via an arthropod
  vector