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1. What are the three main modes of transmission of infectious agents?
Give an example of each mode.
- The three main modes of transmission are contact, droplet and airborne.
Contact transmission occurs when an infected person or a contaminated
object directly or indirectly touches a susceptible host. An example is
skin-to-skin contact with a person who has chickenpox. Droplet
transmission occurs when respiratory droplets from an infected person are
propelled by coughing, sneezing or talking to the mucous membranes of a
susceptible host. An example is influenza. Airborne transmission occurs
when small particles containing infectious agents remain suspended in the
air and are inhaled by a susceptible host. An example is tuberculosis.
2. What is the difference between horizontal and vertical transmission of
infectious agents? Give an example of each type.
- Horizontal transmission is the transfer of infectious agents from one
individual to another within the same generation or population. An
example is sexual transmission of HIV. Vertical transmission is the
transfer of infectious agents from a parent to an offspring, either before or
after birth. An example is congenital syphilis.
3. What are the four factors that influence the transmission of infectious
agents? Explain how each factor affects transmission.
- The four factors are agent, host, environment and time. Agent refers to
the characteristics of the infectious agent, such as virulence, infectivity,
pathogenicity and antigenicity. These determine how easily and how
severely the agent can infect and cause disease in a host. Host refers to the
characteristics of the susceptible host, such as immunity, genetic
susceptibility, age, sex, behavior and health status. These determine howÂ
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