an update and forecast of the Ebola outbreak elicited jointly by StratAdviser Ltd and the Fench Society of Disaster Medicine

2. Current Ebola outbreak
is like none before
Cases, 1,848
Deaths, 1,013
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
2,000
Su,DRC
DRC
n/a
Su
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
CdI,Ga
DRC
Ga
n/a
n/a
n/a
Ug
Ga
Co
Co
Su
Co
n/a
DRC,Ug
DRC
n/a
n/a
Ug
DRC
Ug
Gu,Li,SL,Ni
197619771978197919801981198219831984198519861987198819891990199119921993199419951996199719981999200020012002200320042005200620072008200920102011201220132014
AxisTitle
Number of cases/deaths per year since first outbreak
Wednesday, August 13, 2014 StratAdviser/SFMC Dr Jan-Cedric Hansen 2

3. Epidemiologic specificity of
current Ebola outbreak
You can’t get Ebola through air (vs Influenza)
– Neither through water nor food
You get Ebola through body fluids and fomites
– Mucosa contact at higher risk than skin
Only families and friends are at risk
– because they come in close contact with infectious
secretions when caring for ill individuals
Standard European Hospital Hygiene protects
– Gloves, Gown (fluid resistant or impermeable), Eye
protection (goggles or face shield), Facemask, hand
washing, …
Wednesday, August 13, 2014 StratAdviser/SFMC Dr Jan-Cedric Hansen 3

4. So how come the cumulative figure
is this one !
cumulated numbre of case,
4,235
cumulated number of death,
2,603
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
AxisTitle
4 774: threshold of x2 cases before 2014
3 180: threshold of x2 deaths before 2014
Wednesday, August 13, 2014 StratAdviser/SFMC Dr Jan-Cedric Hansen 4

5. Because …
Health Authorities use standard epidemic compartmental
models to build on their response plan
– SIR (Susceptible–Infectious–Removed)
– SEIR (Susceptible-Exposed-Infectious-Removed)
Those epidemic models are based on the assumption
that :
– Behaviour of all parameters is homogeneous throughout models
– The number of secondary cases generated by an index case in
the absence of control interventions is between 1.83 and 1.34
(R0)
– Control measures (including education and contact tracing
followed by quarantine) are implemented immediately
– Efficacy of control measures is optimal thus reducing the final
epidemic size by a factor of 2
Wednesday, August 13, 2014 StratAdviser/SFMC Dr Jan-Cedric Hansen 5

6. Unfortunately …
Heterogeneity exists:
– Heterogeneous spatial distribution of host populations
– Heterogeneous health status of populations (multi-
hosts for many diseases such as HIV and pandemic
influenza)
– Heterogeneous susceptibility among age groups and
other social categories
– Heterogeneous social behaviour among groups
regarding caring of their relatives or friends
There also exists an epidemic equilibrium:
– either a globally attracting disease-free equilibrium
– or a globally attracting endemic equilibrium
Wednesday, August 13, 2014 StratAdviser/SFMC Dr Jan-Cedric Hansen 6

7. It impacts epidemic models
The Department of Mathematics and Statistics,
University of Victoria, BC, Canada demonstrated in
2012 that:
– If R0 ≤ 1, then the disease-free equilibrium is globally
asymptotically stable and the disease dies out from all
groups or stages
– If R0 > 1, then the disease persists in all groups or stages,
and the endemic equilibrium is globally asymptotically
stable
As stated in a previous slide
for Ebola 1.34 < R0 ≤ 1.83
– The Ebola outbreak is likely to become
endemic in West Africa
Wednesday, August 13, 2014 StratAdviser/SFMC Dr Jan-Cedric Hansen 7

8. References of interest
– Hae-Wol Cho, Chaeshin Ch. A Tale of Two Fields:
Mathematical and Statistical Modeling of Infectious
Diseases. Osong Public Health Res Perspect. 2011
September; 2(2): 73–74.
– Shuai Z & van den Driessche P. (2012). Impact of
heterogeneity on the dynamics of an SEIR epidemic
model. Math. Biosci. Eng, 9(2), 393-411.
Wednesday, August 13, 2014 StratAdviser/SFMC Dr Jan-Cedric Hansen 8

9. Contacts for more advices
StratAdviser Ltd
– 2nd Floor, Berkeley Square
House, London, W1J 6BD UK
• Phone: +44 (0) 207 8874510
• Fax:+44 (0) 207 8876001
• www.stratadviser.com
• contact@stratadviser.com
– Dr Jan-Cedric Hansen
• Mobile UK: +44 (0) 796 4330504
• Mobile F: +33(0) 631830868
• jc.hansen@stratadviser.com
Société Française de
Médecine de Catastrophe
– 38 rue Dunois - 75647 PARIS
Cedex 13 France
• Tel : +33(0)6 43 26 81 51
• medecine.cata@gmail.com
• http://www.sfmc.eu
• med.cata@gmail.com
Wednesday, August 13, 2014 StratAdviser/SFMC Dr Jan-Cedric Hansen 9