Lecture 18

Question 1

All pathogens must complete infectious disease cycle

Reservoirs

Answer 1

Reservoir transmission to host to reservoirs

Reservoirs = natural habitat of microbe that supports growth and survival, where infection begins

Animal reservoirs = zoonotic diseases

Environmental reservoirs (soil, water)

Human reservoirs
-No symptoms = carrier who can still transmit

Question 2

Mechanisms of Transmission

Contact Transmission

2 forms

Answer 2

Most common mode of transmission

1. Direct contact transmission
   - direct physical contact
2. Indirect contact transmission
   (microbe from an infected person to an intermediate then to a person)
   -Vehicles = contaminated food or water
   -fomites = contaminated inanimate objects (cups door)
   -Vectors = animals or insects

Question 3

Mechanisms of Transmission

Droplet Transmission

Airborne Transmission

Answer 3

Drops of respiratory secretions that are inhaled
-travel less than 1m from source

Released into air then float freely or become associated with dust particles and move in air
-more then 1 M from source

Both similar, not the same, different precautions

Question 4

How to prevent spread of diseases 3 steps

Eliminate The Reservoir
Limit The availability
Prevent transmission

Answer 4

Eliminate the reservoir (control disease at source)

• animal = immunization or killing
• Environment = decontaminate or avoid contact
• Human = isolate/ treat infected host (harder for carriers)

Limit the availability of new hosts

• Improve living conditions, general health/nutrition = strong immune system
• vaccination

Prevent transmission (minimize risk)

• Indirect contact (clean, remove vectors)
• Airborne (air flow systems = negative pressure)
• Droplet, Direct contact(barrier precautions, wash hands)

Question 5

Preventing infectious disease on inter/national level needs disease control network

Answer 5

Network of people who identify track and control diseases (health care workers, epidemiologists, diag. labs, public health orgs.)

Question 6

On a WorldWide level, what public health practice has been most effective at decreasing incidence of infectious diseases

1 to 5

Do they work?

Issues remaining?

Answer 6

1. Clean drinking water
2. Clean food
3. Promoting sanitation and person hygiene
4. Controlling insect vectors
5. Public education campaigns on STIs and Resp. disease

Public health efforts working in last 100 years

1. Varies globally how well it works
2. New diseases appear

Question 7

Healthcare Associated Infections HAIS (Nosocomial/ hospital acquired infections)

Answer 7

Disease gotten during healthcare or giving it

• Pt to pt
• healthcare provider to pt (vice versa)
• Environment to pt

All healthcare settings

Question 8

What things cant put pts in a healthcare facility at risk for contracting HAIS

3

Answer 8

1. Pt health status and type of medical procedure
   - immunocompromised increased risk of infection
   - direct entry into blood or tissue procedure (suture, surgery, catheterization)
2. Characteristics of the microbe to which pt is exposed (does it form biofilm, can it produce spores)
3. The environment (physical surrounds and infrastructure)
   - Lots of movement, over crowding, bad sanitation

Question 9

What HAI risks to health care providers

2

Answer 9

1. Infections from pt by airborne, droplet, contact(Resp. gastrointestinal, skin infections)
2. Infection from accidental exposure (blood and fluid)

Question 10

Preventing HAI

Answer 10

Routine (standard) precautions supplemented by additional precautions

• routine = all patients
• additional = known or suspected contagious pathogen

Ensuring policies and procedures followed is job of institutions infection control practitioner

Question 11

3 basic elements of Routine precautions

Answer 11

1. Risk Assessment
   - Assess risk of transmission before encounter
2. Risk Reduction Strategies (based on risk)
   - PPE, Cleaning, Separate room or ward
3. Education

Question 12

Additional Precautions

-when routine is not enough based on risk

Answer 12

• used for known or suspected infectious pathogens
• supplement not replace routine
• droplet, contact, airborne

Question 13

Handwashing

and When you must 5

Answer 13

Most effective way to reduce infection caused by direct contact transmission
-45% reduction of illness after handwashing at navy

1. before touching pt
2. before clean/aseptic procedure
3. After body fluid exposure risk
4. After touching pt
5. After touching pt surrounding

Note: not sterilize but removed transient microbes so you cant transmit