Post on 04-Jan-2016
Bogota workshop on health services pandemic preparedness
Dr. Oscar J Mújica; DPC/PAHO
Bogota; COLOMBIAApril 19-21, 2006
Pandemic Impact Assessment
pandemic influenza pandemic influenza isis a real & serious a real & serious disease… disease…
Hien TT et al., New England J Med 2004;350:1179-1188
DAY 5 DAY 7 DAY 10
Bogota workshop on health services pandemic preparedness
the modeling problemthe modeling problem
influenza pandemics in 20th Century: 1918; 1957; 1968
massive & notable impacts
experts predict another pandemic: can not reliable predict when
can not reliable predict how, who, where
plan for next pandemic: it is a global health priority
need numbers
Bogota workshop on health services pandemic preparedness
PAHO/CDC pandemic impact assessment PAHO/CDC pandemic impact assessment workshopsworkshops
to estimate the burden of disease attributable to influenza pandemic: excess of deaths, hospitalizations, and outpatient visits
to evaluate the response capacity (i.e., the potential to cope with excess demand) from hospitals and outpatient health facilities (surge capacity)
to estimate the magnitude of the loss of workdays
to derive gross estimates of direct economic impact attributable to pandemic influenza
Bogota workshop on health services pandemic preparedness
FluSoftware: FluAid, FluSurge & FluSoftware: FluAid, FluSurge & FluWorkLossFluWorkLoss
Bogota workshop on health services pandemic preparedness
1957-58 influenza pandemic: geographic 1957-58 influenza pandemic: geographic spreadspread
02/57
04/57
06/57
05/57
06/57
07/57
08/57
06/57
07/57
C.W. Potter, Textbook of Influenza, 1998
Bogota workshop on health services pandemic preparedness
resource availability for influenza pandemic:Physicians: 30%
Registered nurses: 40%hospital beds: 25%
availability of morgue slots (as a % of the total number of hospital beds): 5% 10% in Northern Americaduration of (first) pandemic wave: 8 weeksestimated rate of outpatient visits: 20 flu patients/caretaker/day
average hospital stay (bed occupancy due to flu): 1 weeks
minimum most likely maximum
high 0.126 0.220 7.650non-high 0.014 0.024 0.125
high 0.100 2.910 5.720non-high 0.025 0.037 0.090
high 2.760 4.195 5.630non-high 0.280 0.420 0.540
high 2.100 2.900 9.000non-high 0.200 0.500 2.900
high 0.830 2.990 5.140non-high 0.180 1.465 2.750
high 4.000 8.500 13.000non-high 1.500 2.250 3.000
high 289.0 346.0 403.0non-high 165.0 197.5 230.0
high 70.0 109.5 149.0non-high 40.0 62.5 85.0
high 79.0 104.5 130.0non-high 45.0 59.5 74.0
Risk Distribution (rates per 1,000 pop)
age group risk1968 pandemic scenario
Mortality
0 - 19
19 - 64
65+
Hospitalization
0 - 19
19 - 64
65+
Outpatient Visits
0 - 19
19 - 64
65+
FluSoft modeling data & assumptionsFluSoft modeling data & assumptions
Bogota workshop on health services pandemic preparedness
default values: US national estimates; CDC's Advisory Committee on Immunization Practices, ACIP
lowest 15medium 25highest 35
clinical attack rate (%)
default LAC0 - 14 6.4 11.215-64 14.4 18.065+ 40.0 45.0
agegroupHigh-Risk Prevalence
FluSoft modeling data & assumptionsFluSoft modeling data & assumptions
Bogota workshop on health services pandemic preparedness
FluSoft modeling data & assumptionsFluSoft modeling data & assumptions
Bogota workshop on health services pandemic preparedness
other assumptions: employment & marriage rate
?01/19
03/1804/18
06/18
05/18
06/18
06/18
?
C.W. Potter, Textbook of Influenza, 1998
1918-19 influenza pandemic: geographic 1918-19 influenza pandemic: geographic spreadspread
Bogota workshop on health services pandemic preparedness
1918 pandemic influenza case fatality rate
gender weighted average case fatality rates locales* 0 14 y.o. 15 64 y.o. 65+ y.o.
locales 1 1.3% 2.6% 4.4% locales 2 0.7% 1.3% 1.9% locales 3 0.9% 3.5% 6.4%
average 0.96% 2.46% 4.21%
FluSoft modeling data & assumptionsFluSoft modeling data & assumptions
Bogota workshop on health services pandemic preparedness
Locales, all US: 1 (New London; Baltimore; Maryland); 2 (Macon; Spartanburg; San Antonio; Augusta; Des Moines; Little Rock; Louisville); 3 (San Francisco)
age group (years) distribution of cases
by age group (%)
0 14 años 47.6% 15 65 años 48.9%
65+ años 3.5%
Frost WH. Public Health Reports 1920;35:584-97
FluSoft modeling data & assumptionsFluSoft modeling data & assumptions
Bogota workshop on health services pandemic preparedness
minimum most likely maximum
high 1.508 2.633 91.546non-high 0.168 0.287 1.496
high 0.886 25.780 50.675non-high 0.221 0.328 0.797
high 9.261 14.076 18.891non-high 0.940 1.409 1.812
Risk Distribution (rates per 1,000 pop)
age group risk1918 pandemic scenario
Hospitalization
0 - 19
19 - 64
65+
0-19 y.o. 11.9668119-64 y.o. 8.85917965+ y.o. 3.355454
1918 scaling factor
The scaling factor was obtained by comparing the calculated death rates, by age group, from estimates of death for the U.S. population
estimated pandemic impact in the worldestimated pandemic impact in the world
500 (23)1,253 (59)Ill, self care
Maximum (%)Minimum (%)
2,137 (100)2,136 (100)Totals
1,601 (75)875 (40)Very ill**
28.1 (1.3)6.4 (0.3)Seriously ill*
7.4 (0.3)2 (0.2)Deaths
Global totals (millions)Outcomes
500 (23)1,253 (59)Ill, self care
Maximum (%)Minimum (%)
2,137 (100)2,136 (100)Totals
1,601 (75)875 (40)Very ill**
28.1 (1.3)6.4 (0.3)Seriously ill*
7.4 (0.3)2 (0.2)Deaths
Global totals (millions)Outcomes
clinical attack rate = 35%; first pandemic wave (8 weeks)
* Ideally, be hospitalized ** Ideally, see a medical doctor Dr. M. Meltzer, CDC; personal communication
Bogota workshop on health services pandemic preparedness
estimated pandemic impact in the USestimated pandemic impact in the US
1.9 million209,000Deaths
742,50064,875Mechanical ventilation
1.485 million128,750ICU care
9.9 million865,000Hospitalization
45 million45 millionOutpatient medical care
90 million90 millionIllness
Severe (1918-like)
Moderate 1958/68-likeCharacteristic
1.9 million209,000Deaths
742,50064,875Mechanical ventilation
1.485 million128,750ICU care
9.9 million865,000Hospitalization
45 million45 millionOutpatient medical care
90 million90 millionIllness
Severe (1918-like)
Moderate 1958/68-likeCharacteristic
Source: U.S. Dept Health and Human Services Pandemic Influenza Plan: Part 1. Page 18.Available at: http://www.dhhs.gov/pandemicflu/plan/pdf/part1.pdf
Bogota workshop on health services pandemic preparedness
estimated potential impact in LACestimated potential impact in LAC
clinical attack rate = 25%; first pandemic wave (8 weeks)FluAid/FluSurge modeling – Pandemic Impact Subregional Workshops Nov/Dec 2005
Bogota workshop on health services pandemic preparedness
1968 1918moderate severe
334,163 2,418,469[131,630 - 654,960] [627,367 - 5'401,035]
1,461,401 11'798,613[459,051 - 1'937,503] [3'189,747 - 16'418,254]
76,187,593 68'470,386[59'738,730 - 109'207,769] [58'114,124 - 92'227,761]
* annual average burden of mortality observed': 3'410,000 deaths
outpatient visits
probable health impact
pandemic scenario
deaths *
hospitalizations
estimated potential impact in LACestimated potential impact in LAC
pandemic scenario
health outcome range MexicoCentral
AmericaThe
CaribbeanAndean
AreaBrazil
Southern Cone
most likely 61,148 20,538 25,860 68,865 113,416 44,336minimum 22,721 7,454 11,048 25,367 44,075 20,965
maximum 122,131 43,207 49,136 138,721 220,044 81,721
most likely 272,150 93,564 110,024 307,922 495,422 182,319minimum 83,209 28,736 35,971 93,963 153,921 63,251
maximum 362,724 130,059 144,357 412,889 648,852 238,622
most likely 14,552,192 5,503,786 5,479,122 16,717,177 25,202,794 8,732,522minimum 11,401,412 4,339,647 4,300,140 13,108,492 19,708,912 6,880,127
maximum 20,792,426 7,707,972 7,904,874 23,812,305 36,354,664 12,635,528
most likely 451,833 153,668 181,273 510,658 823,686 297,351minimum 111,698 37,663 50,474 125,526 210,621 91,385
maximum 1,024,158 372,261 393,990 1,169,314 1,808,203 633,109
most likely 2,228,186 778,060 868,259 2,529,440 3,999,208 1,395,460minimum 595,520 213,389 238,688 677,652 1,067,437 397,061
maximum 3,122,762 1,152,739 1,190,685 3,573,889 5,472,072 1,906,107
most likely 13,094,642 4,911,408 4,990,981 15,060,771 22,594,485 7,818,098minimum 11,100,064 4,177,383 4,230,699 12,765,345 19,168,387 6,672,247
maximum 17,569,963 6,668,192 6,532,503 20,131,106 30,675,158 10,650,839
Disease Control & Prevention, DPC; PAHO/WHO, Washington DC 2005
deaths
hospitalizations
outpatient visits
deaths
hospitalizations
outpatient visits
1918
1968
Clinical Attack rate = 25%; first 8-week pandemic wave
Bogota workshop on health services pandemic preparedness
Latin America & the Caribbean:Latin America & the Caribbean:distribution of hospital admission excessdistribution of hospital admission excess
(AT25%; scenario 1968; 1st pandemic wave)
0
10000
20000
30000
40000
50000
60000
70000
1 8 15 22 29 36 43 50
Days of outbreak
Dai
ly #
of a
dmis
sion
s
Bogota workshop on health services pandemic preparedness
Latin America & the Caribbean:Latin America & the Caribbean:potential pandemic impact on health servicespotential pandemic impact on health services
(AT25%; scenario 1968; 1st pandemic wave)
1 2 3 4 5 6 7 8
weekly admissions 88,408 147,346 221,020 279,958 279,958 221,020 147,346 88,408
peak admissions/day 43,626 43,626
N° of influenza patients in hospital 40,138 66,897 100,345 127,104 129,608 108,611 81,515 52,813
% of hospital capacity needed 26% 43% 65% 82% 84% 70% 53% 34%
N° of influenza patients in ICU 13,261 28,123 43,187 57,046 61,737 60,057 47,722 32,952
% of ICU capacity needed 98% 209% 321% 423% 458% 446% 354% 245%
N° of influenza patients on ventilators 6,631 14,061 21,594 28,523 30,868 30,029 23,861 16,476
% usage of ventilator 344% 730% 1122% 1482% 1604% 1560% 1240% 856%
Hospital Admission
Hospital Capacity
ICU Capacity
Ventilator Capacity
weekPotential Impact on Hospital Surge Capacity
Bogota workshop on health services pandemic preparedness
Latin America & the Caribbean:Latin America & the Caribbean:workdays loss attributable to influenza pandemicworkdays loss attributable to influenza pandemic
Work days lost; LAC scenario 196815% 25% 35%
most likely 309,023,424 515,039,041 721,054,657minimum 283,542,305 472,570,509 661,598,713maximum 344,182,797 573,637,995 803,093,194
Work days lost; LAC scenario 191815% 25% 35%
most likely 437,899,073 729,831,789 1,021,764,463minimum 339,780,057 566,299,961 792,820,047maximum 535,941,384 893,235,692 1,250,529,924
Bogota workshop on health services pandemic preparedness
Latin America & the Caribbean:Latin America & the Caribbean:costs from workdays lost due to pandemic costs from workdays lost due to pandemic
influenzainfluenza
Costs of Work days lost ($ppp); LAC scenario 196815% 25% 35%
most likely 9,004,942,587 15,008,237,645 21,011,532,703minimum 8,262,422,778 13,770,704,630 19,278,986,482
maximum 10,029,486,711 16,715,811,186 23,402,135,660
Costs of Work days lost ($ppp); LAC scenario 191815% 25% 35%
most likely 12,760,378,982 21,267,298,343 29,774,216,459minimum 9,901,190,869 16,501,980,870 23,102,776,169
maximum 15,617,331,932 26,028,888,071 36,440,441,997
Bogota workshop on health services pandemic preparedness
Latin America & the Caribbean:Latin America & the Caribbean:non-discounted value of human life lost due to non-discounted value of human life lost due to
influenza pandemic ($ppp)influenza pandemic ($ppp)
scenario 15% 25% 35%
1968-like 5,013,896,236 8,356,485,392 11,699,074,5471918-like 39,386,141,711 65,643,564,602 91,900,987,220
direct cost from excess hospitalization (ICU & non-ICU) and excess outpatient visits has not yet been summarized.
Bogota workshop on health services pandemic preparedness
on estimations…on estimations…
they are PRELIMINARY, and EXPLORATORY
they are ILLUSTRATIVE
they are NOT PREDICTIONS of what inevitably may happen
they should serve as an AID IN PLANNING
Bogota workshop on health services pandemic preparedness
Bogota workshop on health services pandemic preparedness
Dr. Oscar J Mújica; DPC/PAHO
Bogota; COLOMBIAApril 19-21, 2006
a primer on transmission dynamics(or how pandemic influenza will move among us…)
what good are models…?what good are models…?
first, because life is full of choices, risks, uncertainty, and trade-offs
then, because we do need to make sound decisions in a setting of absence of absolute certainty (and we do need a rationale for them)
and then because sound decisions demand evidence, structure, consistency, and simplification:
models illustrate level of knowledge
models show how we think things are connected and happen
models add simplification = helps clarify
models can help identify what is “most important”
sensitivity analyses, confidence intervals
no single answer
Bogota workshop on health services pandemic preparedness
0
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DAY
CASES
first case
outbreak detection & responseoutbreak detection & response
Bogota workshop on health services pandemic preparedness
detection/report
laboratoryconfirmationresponse
opportunity for control
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DAY
CASES
opportunity for control
first case
detectionreport
laboratoryconfirmation response
timelytimely outbreak detection & response outbreak detection & response
Bogota workshop on health services pandemic preparedness
pandemic spread potentialpandemic spread potential
0
1,000
2,000
3,000
4,000
5,000
case
s
1 2 3 4 5
time
What must happen at time 4 for this event to continue be seen as a public health problem?
Basically, an equal number of incident (new) cases must be generated in the population per unit time…
In other words, the ‘goal’ for each new case at time t is “to infect one” up to time t+1
Bogota workshop on health services pandemic preparedness
to understand this, we need to build a to understand this, we need to build a model…model…
Why? –because we need evidence, structure, consistency, and simplification in order to make sound decisions…
)1(sin txyNxtd
xd
N = total populationX = number of susceptible persons (as a fraction of N)Y = number of infectivesµ = death rateΒ = transmission rateδβ = force of infectionω = angular frequency or oscillation in susceptibility
At any given moment in time, the fraction of susceptible persons in a population is dependent upon (a function of) the number of susceptible persons who die minus the number of susceptible persons who become infective. The latter fluctuates in a cyclical pattern.
Duncan et al. The dynamics of measles epidemics. Theoret Pop Bio 1997;52:155-163
Bogota workshop on health services pandemic preparedness
pandemic spread potentialpandemic spread potential
k . β . D = 1
transmission efficiency
rate of infective contact
duration of infectivity
R0 =
R0 = basic reproductive rate of an epidemic
Bogota workshop on health services pandemic preparedness
pandemic influenza: propagation pandemic influenza: propagation dynamicsdynamics
duration of infectivity (D, days)
2
3
65
4
7
0
10
20
30
40
50
60
70
80
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
transmission efficiency (B)
infe
ctiv
e c
onta
ct r
ate
(num
ber/
week)
Bogota workshop on health services pandemic preparedness
so, let’s build a simple model…so, let’s build a simple model…
influenza pandemic propagation:
assume a basic reproductive rate (Ro) = 1.5
assume an average generation time (days) = 3.0
then repeat …
A B C
1
díanúmero de
casos nuevos
total acumulado
2 0 1 13 3 2 34 6 2 55 9 3 86 12 5 137 15 8 218 18 11 329 21 17 49
daynumber of new cases
cummulative total
multiply this number times 1.5 …
then place answer in cell bellow …
new cases are being
generated every 3 days…
Bogota workshop on health services pandemic preparedness
pandemic spread according to our simple pandemic spread according to our simple model…model…
0
20
40
60
80
100
120
140
160
180
0 3 6 9 12 15 18 21 24 27 30
days
case
s
incidence
cummulative incidence
Bogota workshop on health services pandemic preparedness
epidemic propagation scenariosepidemic propagation scenarios
0
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400
600
800
1000
1200
1 2 3 4 5 6 7 8 9 10 11 12
tiempo
0
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800
1000
1200
1 2 3 4 5 6 7 8 9 10 11 12
tiempo
0
200
400
600
800
1000
1200
1 2 3 4 5 6 7 8 9 10 11 12
tiempo
R0 > 1
epidemic expansion
R0 = 1
epidemic equilibrium
R0 < 1
epidemic contraction
R0 = basic reproductive rate of an epidemic
Bogota workshop on health services pandemic preparedness
epidemiological ‘goal’ for outbreak epidemiological ‘goal’ for outbreak containmentcontainment
0
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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
t
c
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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
t
c
…it is imperative to quickly reduce R0 in situ (locally)
Bogota workshop on health services pandemic preparedness
correlation of interventionscorrelation of interventionsfor pandemic containmentfor pandemic containment
personal protective equipment
isolation, quarantine &
social distance
transmission efficiency
rate of infective contact
duration of infectivity
antiviral prophylaxis and therapy
k . β . D = 1R0 =
Bogota workshop on health services pandemic preparedness
pandemic influenza: potencial for pandemic influenza: potencial for containmentcontainment
duration of infectivity (D, days)
2
3
65
4
7
0
10
20
30
40
50
60
70
80
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
transmission efficiency (B)
infe
ctiv
e c
onta
ct r
ate
(num
ber/
week)
Longini IM et al; Science 2005:309
AvT: antiviral therapy
Pv: pre-vaccination
AvCp: antiviral chemoprophylaxis
Q&I: quarantine & isolation
2
1
0
3
R0AvT1.6
Q&I + Pv + AvCp
2.4
Pv + AvCp2.10
10
20
30
40
50
60
70
80
90
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
t
c
0
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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
t
c
Bogota workshop on health services pandemic preparedness
pandemic containment: evidence from pandemic containment: evidence from modelingmodeling
Longini IM et al; Science 2005:309
Bogota workshop on health services pandemic preparedness
0
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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
t
c
pandemic containment: evidence from pandemic containment: evidence from modelingmodeling
GTAP: Geographically Targeted Antiviral Profilaxis Longini IM et al; Science 2005:309
Bogota workshop on health services pandemic preparedness
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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39
t
c
pandemic containment: evidence from pandemic containment: evidence from modelingmodeling
Longini IM et al; Am J Epidemiol 2004:159
Bogota workshop on health services pandemic preparedness
pandemic containment: evidence from pandemic containment: evidence from modelingmodeling
Longini IM et al; Am J Epidemiol 2004:159
Bogota workshop on health services pandemic preparedness
the most certain model…the most certain model…
Bogota workshop on health services pandemic preparedness
time (weeks)
impact
disease burdenHS surge capacityeconomic & social
unprepared
prepared
as a way of conclusion…as a way of conclusion…
Plan, Plan, Plan…
Prepare, Prepare, Prepare…
Practice, Practice, Practice…
What to do…?, Take “home message”…?
Bogota workshop on health services pandemic preparedness