Biology Reference
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amended. At a basic level, the accuracy of the HealthMap classifier can be
measured by the percentage of reports entering the system that need not
have their classifications corrected in any way. In more detailed analysis, the
number of alerts requiring a correction of disease classification as compared
with the number requiring a location correction can be examined. These
analyses of manual corrections allows for the overall accuracy of the system
to be continuously studied (Freifeld et al. 2008).
In addition to correcting misclassifications, the human analyst adds pre-
cise location information when that level of information is available within a
given alert. In summary, although HealthMap currently relies on significant
manual curation, one future objective of the system is to maximize automa-
tion, in order to minimize laborious classifications and leverage the human
contribution (Freifeld et al. 2008).
6.4 Data Dissemination
Reducing information overload and providing users with news of immedi-
ate interest is of particularly high importance to HealthMap. The filtering
and visualization features of HealthMap serve to bring structure to an other-
wise overwhelming amount of information, enabling the user to quickly and
easily find those elements pertinent to his or her area of interest. Since not all
information collected has relevance to every user, only articles classified as
“breaking” and “warning” are posted to the HealthMap Web site in order to
provide focused news of immediate interest (Brownstein et al. 2008; Keller
et al. 2009; Freifeld et al. 2008).
After being collected, the data are aggregated by source, disease, and
geographic location and then overlaid on to an interactive map (Keller et al.
2009). The user controls within the interactive map include the ability to
select which data feeds (sources), diseases, and geographical regions are dis-
played (Keller et al. 2009). Clicking on a country name zooms the map view
to that country for easy viewing of alerts in that specific location. A date
slider below the map allows the user to control the date range of displayed
alerts. The user can set a start and end date at any point in the previous 30
days. “Full Screen” mode expands the map to cover the full browser window,
allowing for richer visual display and navigation. Lastly, the color of each
marker on the map indicates the “Heat Index” value for the location, with
the deeper red color indicating more intense recent activity as contrasted by
the paler yellow color (Freifeld et al. 2008). This “Heat Index,” or composite
activity score, is calculated based on both the reliability of the data source
and the number of unique data sources. Alerts from governmental agencies
(e.g., CDC, EuroSurveillance), international organizations (e.g., WHO), and
expert-moderated services (e.g., ProMED-mail, CIDRAP) typically provide
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