Spread of Pathogens - Environment

Question 1

What are the main mechanisms of environmental spread of pathogens?

Answer 1

• Faecal-oral
• Aerosol
• Vector-bourne
• Zoonotic
• Direct contact

Question 2

What are the main modes of respiratory pathogen transmission?

Answer 2

• Large droplets
• Aerosols (airbourne)
• Fomites (surface contamination)

Question 3

Example of pathogen that spreads via large respiratory droplets

Answer 3

Influenza- short range transmission

Question 4

Example of pathogen that spreads via aerosols

Answer 4

Mycobacterium tb- remain suspended in air; infect over longer distances

Question 5

What structural feature allows M. tb to be transmitted as aerosol?a

Answer 5

Waxy, lipid-rich cell wall full of mycolic acids resists dessication

Question 6

How does Sars-Cov-2 spread?

Answer 6

Via both large droplets and aerosols

Question 7

What enables fomite transmission of some respiratory pathogens?

Answer 7

Environmental stability, especially in non-enveloped viruses like Adenovirus

Question 8

What’s the difference between enveloped and non-enveloped viruses in terms of stability?

Answer 8

Enveloped viruses are fragile (e.g., Influenza); non-enveloped viruses are more stable on surfaces (e.g., Adenovirus).

Question 9

How does humidity affect respiratory virus transmission?

Answer 9

Low humidity increases aerosol survival and transmission (e.g., Influenza more prominent in winter).