General outbreak control

Question 1

9 steps in outbreak control

Answer 1

1. Establish a team, lab support, comms
2. Confirm the existence of an outbreak
3. Define a case, find and count cases (line list)
4. Environmental investigations
5. Descriptive epidemiology (time, place, person)
6. Generate and test hypothesis based on analytical epi
7. Initiate control and prevention measures
8. Initiate further surveillance or a more systematic study if necessary
9. Report and disseminate findings

Question 2

What are the broad strategies to control infectious diseases? (11)

Answer 2

Public health legislation and regulation
Environmental health sanitation and control of water, food, waste and air
Surveillance
Immunisation
Isolation and quarantine
Investigation and control of outbreaks
Case-finding, contact tracing and screening
Education and training of health professionals
Education of the public and people at risk
Hygiene and infection control
Treatment of infections

Question 3

What are the 4 major factors that determine the impact an infection will have on an individual or community?

Answer 3

1. Organism characteristics (lifecycle, reservoir, source, ability to survive in environment, how it replicates, size of infectious dose, pathogenicity)
2. Host characteristics (immunity, immunosuppression, risk behaviours e.g. IVDU)
3. Transmission characteristics (air, droplet, direct contact, water, fecal-oral, sexual)
4. Environment (temp, humidity, dust, sanitation, vectors)

Question 4

How do you calculate the herd immunity threshold?

Answer 4

1-1/R0 (e.g. measles = 1-1/18 = 94%

Question 5

What is the R0 (and herd immunity threshold) of

• measles
• influenza
• pertussis

Answer 5

measles = 15-18 (94-95%)
influenza = 2-3 (60-70%)
pertussis = 12-15 (93-94%)