Global Pandemics

Question 1

Background on Flu

Answer 1

flu viruses make small changes in the viral proteins (antigens) so infection does not provide future protection
Flu epidemics kill about 500k every year
Large antigen changes (crossing species eg birds) so possibility of global pandemic, due to lack of resistance
Pandemic if passes between people
If viruses acquire this ability, it would take 6-8 moths to develop a vaccine
Need other strategies during first few months of a pandemic- need to understand how flu pandemics spread both over time and geographically

Question 2

William Budd 1811-1876

Answer 2

Physician & Epidemologist
Pioneer in the isolation of infectious disease
Mapped Distribution of Cholera in Britian in 1832
Clustered in lower bits - Pattern- Explanation- Action
Became in charge of water supply
Impact- credited with decreasing the incidence of deaths in Bristol from cholera from 2000 per 140,000 in 1849 to just 29 in 1866

Question 3

Geographers approach

Answer 3

abstraction- simplify to get at key processes and identities
Identify regularities across time and space
Capture regularities in equations (modelling)
Predict future patterns of spread
Control- the importance of spatial processes
Not- why did this individual on this particular day become infection, but aggregate patterns of flow

Question 4

Reproduction Rate

Answer 4

Infection rate

RR is the number of cases one case generates on average over the course of its infection period

If less than 1 - no epidemics

Question 5

Contagious process

Answer 5

Starts in cities spreads away furtherest away place is slowest to get to

Wave spreading, relatively slow

Undeveloped places

Question 6

Hierarchical

Answer 6

Spreading jumps from biggest place, to second biggest places, to 3rd etc

Fast

Developed places

Question 7

Control strategies

Answer 7

Vaccines

Spatial Barriers

Question 8

Local elimination

Answer 8

vaccinate locally to break chain of infection ie to reduce RR
Flu- very difficult virus change needed 8-9 months to develop vaccine, therefore use general anti-viral drugs to reduce period of infectivity, but infectious before clinical signs

Question 9

Defensive isolation

Answer 9

erect boundaries- do not let infective in- e.g. Historically do not let cats or dogs into britiain to stop spread of rabies
Flu- very challenging as worldwide movement of infective peoples, and infectious before clinical signs

Question 10

Offensive containment

Answer 10

isolate infected place- cordon sanitise= exclusion zone; prevent movement out
Flu- easier to do for animals e.g. Turkey farm but people got out before they knew

Question 11

Global eradication

Answer 11

get rid of it everywhere- great success is smallpox- easily recognisable, lifelong immunity, highly effective vaccine
Flu- the threat is mutating so non of the above applied

Question 12

Important of reproductive rates

Answer 12

If 1.4 no pandemic

If 1.5 pandemic

2.3 (as in 1918) very rapid pandemic

RR < 1.9 AV drugs effective strategy for local containment, even if only treat 5-10%, slows down long enough to develop vaccine

RR > 1.9 even if unrealistic 20% given AV drugs, leaves 30-50% of the world infected before vaccine is developed

Question 13

Comparing scenarios

Answer 13

baseline- no invention
Selfish- each country relies on its own supplies; drugs remain concentrated in the West
Cooperative: countries donate part of their resources for global use
Cooperative strategy shown to be more effective in delaying the pandemic evolution and mitigating its impact on the population of both donor and recipient countries
Even very limited sharing of AV, as long as 10% of stockpiles results in a global deceleration of the pandemic, whereby the peak is delayed by more than one year for RR as high as 1.5-1.9