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ISDS 2012 Conference Abstracts

Disease Models for Event Prediction
Courtney D. Corley*1 and Laura Pullum2

1Pacific Northwest National Laboratory, Richland, WA, USA; 2Oak Ridge National Laboratory, Oak Ridge, TN, USA

Objective
The objective of this manuscript is to present a systematic review

of biosurveillance models that operate on select agents and can fore-
cast the occurrence of a disease event.

Introduction
One of the primary goals of this research was to characterize the

viability of biosurveillance models to provide operationally relevant
information to decision makers, in order to identify areas for future
research. Two critical characteristics differentiate this work from
other infectious disease modeling reviews [1,2]. First, we reviewed
models that attempted to predict the disease event, not merely its
transmission dynamics. Second, we considered models involving
pathogens of concern as determined by the US National Select Agent
Registry.

Background: A rich and diverse field of infectious disease model-
ing has emerged over the past 60 years and has advanced our under-
standing of population- and individual-level disease transmission
dynamics, including risk factors, virulence and spatio-temporal pat-
terns of disease spread. Recent modeling advances include biostatis-
tical methods, and massive agent-based population, biophysical,
ordinary differential equation, and ecological-niche models. Diverse
data sources are being integrated into these models as well, such as
demographics, remotely-sensed measurements and imaging, envi-
ronmental measurements, and surrogate data such as news alerts and
social media. Yet, there remains a gap in the sensitivity and speci-
ficity of these models not only in tracking infectious disease events
but also predicting their occurrence.

Methods
We searched dozens of commercial and government databases and

harvested Google search results for eligible models utilizing terms
and phrases provided by public health analysts relating to biosur-
veillance, remote sensing, risk assessments, spatial epidemiology, and
ecological niche-modeling, This returned 13,767 webpages and
12,152 citations. After de-duplication and removal of extraneous ma-
terial, a core collection of 6,503 items was established, these publi-
cations and their abstracts are presented in a semantic wiki at
http://BioCat.pnnl.gov. Next, PNNL’s IN-SPIRE visual analytics soft-
ware was used to cross-correlate these publications with the defini-
tion for a biosurveillance model. As a result, we systematically
reviewed 44 papers, and the results are presented in this analysis.

Results
The models were classified as one or more of the following types:

event forecast (9%), spatial (59%), ecological niche (64%), diagnos-

tic or clinical (14%), spread or response (20%), and reviews (7%).
The distribution of transmission modes in the models was: direct con-
tact (55%), vector-borne (34%), water- or soil-borne (16%), and non-
specific (7%). The parameters (e.g., etiology, cultural) and data
sources (e.g., remote sensing, NGO, epidemiological) for each model
were recorded. A highlight of this review is the analysis of verifica-
tion and validation procedures employed by (and reported for) each
model, if any. All models were classified as either a) Verified or Val-
idated (89%), or b) Not Verified or Validated (11%; which for the
purposes of this review was considered a standalone category).

Conclusions
The verification and validation (V&V) of these models is dis-

cussed in detail. The vast majority of models studied were verified or
validated in some form or another, which was a surprising observa-
tion made from this portion of the study. We subsequently focused
on those models which were not verified or validated in an attempt to
identify why this information was missing. One reason may be that
the V&V was simply not reported upon within the paper reviewed
for those models. A positive observation was the significant use of
real epidemiological data to validate the models. Even though ‘Vali-
dation using Spatially and Temporally Independent Data’ was one of
the smallest classification groups, validation through the use of actual
data versus predicted data represented approximately 33% of these
models. We close with initial recommended operational readiness
level guidelines, based on established Technology Readiness Level
definitions.

Keywords
Disease models; Event prediction; Operational readiness

References

[1] Lloyd-Smith JO, George DB, Pepin KP, Pitzer VE, Pulliam JRC, Dob-
son A, Hudson PJ, and Grenfell BT. Epidemic Dynamics at the
Human-Animal Interface. Science 4 December 2009: 326 (5958),
1362-1367. [DOI:10.1126/science.1177345]

[2] Bravata DM, Sundaram V, McDonald KM, Smith WM, Szeto H,
Schleinitz MD, et al. Detection and diagnostic decision support sys-
tems for bioterrorism response. Emerg Infect Dis [serial online] 2004
Jan [9-Sept 2012]. http://wwwnc.cdc.gov/eid/article/10/1/03-
0243.htm

*Courtney D. Corley
E-mail: court@pnnl.gov

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e180, 2013