Lecture 38: Epidemiology and Spread of Infectious Diseases

Question 1

Sources of Infections for Humans:

Answer 1

• Animal Reservoirs (Zoonoses) (Rabies, anthrax, ringworm, giardia)
• Nonliving Reservoirs (Soil, water, food)
• Human Carriers/Cases (Typhoid)

Question 2

Transmission mECHANISMS:

Answer 2

- Contact:
Direct
Indirect
Droplet
- Vector:
Mechanical (flies, cockroaches carry passively)
Biological (biting arthropods)

Question 3

Normal healthy human has a _____ microflora.

Answer 3

• Normal

Question 4

Nosocomial Infections are acquired in ____ _____ ______. Exogenous, endogenous - catheters, Iatrogenic:

Answer 4

• Health care facilities
• Exogenous: patient to patient
• Endogenous: catheters, skin to other microflora
• Iatrogenic: doctor induced

Question 5

We have known about the value of hygiene for ___ years. The use of _____ was introduced by Semmelweis. Nightingale emphasised _____ ____, and Lister realised surgical tools needed to be _____.

Answer 5

• 150
• Antiseptics
• Hospital Hygiene
• Sterilised

Question 6

Nosocomial Infections:

Answer 6

• Sick patients are susceptible to infection, especially intensive care unit patients
• Hospitals accumulate primary pathogens

Question 7

Classification of Infectious Diseases, Different systems are used:

Answer 7

• Body Systems
• Taxonomic Groups:
  Staphylococci
  Salmonella
• Longevity and Severity:
  Acute (Common Cold)
  Chronic (TB)
  Subacute (Endocarditis) (Secondary Infections)
  Latent (Herpes, Chicken Pox)

Question 8

Stages of Infectious Diseases:

Answer 8

• Incubation Period
• Prodromal Period
• Illness
• Decline
• Convalescence

Question 9

Incubation period length depends on:

Answer 9

• Virulence
• Dose
• Immune defences
• Pathogen characteristics
• Site of infection
• Min: Less than a day
• Max: More than 10 years

Question 10

The prodromal period is generally….

Answer 10

• A short period of mild symptoms
• Important for differential diagnosis
• Two days: flu
• Seven days: sepsis (meningitis)
• Some viruses can be spread during the prodromal period, before symptoms are showing

Question 11

The illness period is where…

Answer 11

• Characteristic signs and symptoms are most evident
• Immune response not yet helpful
• Generally most infectious stage

Question 12

Decline:

Answer 12

• Immune response or medical intervention leads to decrease in pathogen numbers
• Symptoms subside

Question 13

Convalescence:

Time required depends on:

Answer 13

• Recover from damage caused by pathogen
• Amount of damage
• Nature of pathogen
• Infection site
• Patient health and immune competence

Question 14

Epidemiology of Infectious Diseases:

Answer 14

• Where and when diseases occur and how they are transmitted

Question 15

A disease is epidemic when it occurs in a _____ number of people in a population at the same time. Pandemic = ________, usually worldwide.

Answer 15

• Large

- Widespread

Question 16

Snow’s (1854) Epidemiological study of Cholera:

Answer 16

• Took off a handle of a water pump because he found out cholera was waterbourne
• Now we have sewage systems

Question 17

Epidemiological studies - experimental approach:

Answer 17

• Reporting of clinical cases attending hospitals or medical practices
• Diagnostic follow up to confirm disease incidence/prevalence
• Monitor disease incidence following therapy
• Monitor cases

Question 18

Epidemics may come around due to:

Answer 18

• What’s going on in the country at the time

- Earthquake in Haiti, then Cholera

Question 19

Normally Ebola would be classified as a _______ disease, Zika used to be normal now we can study ______ with it..

Answer 19

• Sporadic

- Hydrocephaly

Question 20

Incidence = ?

Answer 20

• New Cases

Question 21

Prevalance = ?

Answer 21

• Total Cases

Question 22

If incidences peak during summer you can expect that it’s caused by ______.

Answer 22

• Mosquitoes