LG 5.2 - Intro to Infectious Diseases

Question 1

What is an obligate (true, or professional) pathogen?

Answer 1

• Causes disease in virtually any susceptible host including normal, healthy hosts with intact immune systems.
• Produces virulence factors to readily evade host defenses and harm host tissues.

Question 2

What is an opportunistic pathogen?

Answer 2

• Potentially infectious agents that rarely cause disease in individuals with healthy immune systems.
• Not highly virulent.

Question 3

(3)What is the reservoir of an infectious agent? Examples?

Answer 3

• Where the microbe is normally before infecting a susceptible person.
• Humans, animals, vectors (ticks etc.), vehicles (doorknobs etc.)

Question 4

(3)What are some exits from human reservoirs?

Answer 4

• Ear (ear wax)
• Broken skin (blood)
• Skin (flakes)
• Anus (feces)
• Seminal vesicles (semen and lubricating secretions)
• Urethra (urine)
• Eyes (tears)
• Nose (secretions)
• Mouth (saliva, sputum)
• Mammary glands (milk, secretions)
• Vagina (secretions, blood)

Question 5

(3) What are some exits from non-human reservoirs?

Answer 5

• Bugs biting
• Touching vehicles
• Eating food

Question 6

(3) What are some zoonotic transmissions?

Answer 6

• Touching animals
• Eating animals
• Bites scratches
• Contact with products (blankets)
• Fecal-oral
• Contact with urine
• Respiratory route

Question 7

(3) What are some direct modes of transmission? Examples?

Answer 7

• Direct physical contact with blood or body fluids.
• “Person to person transmission”
• Touching, kissing, biting, sex, sneezing, coughing, or talking.

Question 8

(3) What are some examples of vertical transmission?

Answer 8

• Germline
• Prenatal (through placenta)
• Perinatal (contact with anything as they come out)
• Postnatal (breast milk etc.)

Question 9

(3) What are some indirect modes of transmission?

Answer 9

• Infectious agents are transmitted to new hosts through intermediates.
• Airborne, vehicle-borne, vector-borne, zoonotic

Question 10

(3) Horizontal vs. vertical transmission?

Answer 10

• Horizontal: to others.

- Vertical: to your children.

Question 11

(3) What are some infectiousness factors of an infectious agent?

Answer 11

• Time between infection of a person becoming infectious.
• Duration of infectiousness.
• Probability of transmission given a contact between an infectious person and a susceptible person.

Question 12

(3) What are some infectiousness factors of a host?

Answer 12

• Susceptibility of the population.
• Infectiousness of the infected person.
• Infectious dose (how many microbes are necessary to infect someone).

Question 13

(3) What are some infectiousness factors of the environment?

Answer 13

• The type of contacts between infectious and susceptible individuals.
• Number of contacts.

Question 14

(3) What are non-communicable infections?

Answer 14

• Individuals carrying the disease are not likely to spread the disease to others like a dead-end.

Question 15

(4) What are some common routes of transmission?

Answer 15

• Respiratory
• Fecal-oral
• Sexual
• Blood-borne
• Perinatal
• Food-borne
• Water-borne
• Direct contact

Question 16

(4) What are some prevention and control measures for human reservoirs?

Answer 16

• Diagnosis and treatment
• Screening
• Isolation
• Reporting

Question 17

(4) What are some prevention and control measures for animal reservoirs?

Answer 17

• Vaccination
• Treatment
• Euthanasia

Question 18

(4) What are some prevention and control measures for susceptible hosts?

Answer 18

• Vaccination
• Chemoprophylaxis (giving drugs before exposure)
• Maintaining a healthy lifestyle
• Limiting exposure to reservoirs of infection

Question 19

(5) What are the clinical disease host responses, what about subclinical disease host responses?

Answer 19

• Clinical disease: classic and severe disease, moderate severity mild illness.
• Subclinical disease: infection without clinical illness (asymptomatic infection), exposure without infection.

Question 20

(7) What does it mean that viruses are “obligate intracellular parasites”?

Answer 20

• Viruses must generate new progeny inside a host cell.