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is complete. This system is meant to standardize data collection and animal
records across zoological institutions.
Another problem encountered by the WNV surveillance system is one com-
mon to long-term disease studies: changes to the case definition of infection.
At the start of the surveillance system, the CDC defined virus isolation as
the sole means to identify WNV infection. As time progressed, PCR tests for
WNV became more accepted and the case definition expanded (CDC 2004).
Where possible, laboratory results had to be revisited to maintain a consistent
case definition across the study period. Data collection for the surveillance
system also suffered from other problems commonly seen in survey-based
studies, namely, missing data, inconsistent interpretation of questions across
institutions, and loss of information due to open text fields.
A very important lesson learned was to remember the capacity of the diag-
nostic lab before opening the system to too many participants. In the case
of WNV where fears were stoked as the virus continued to expand its geo-
graphic range, the system grew quickly and the diagnostic lab became over-
whelmed. In a less urgent situation, it would be easier to keep sampling to a
minimum or to incorporate more diagnostic labs to help with the testing.
Finally, the importance of following up with participating institutions was
made clear by the fact that many institutions did not report their test results
to their local public health agency. When asked about this later, many par-
ticipants said they did not realize it was their responsibility to report these
results. Intermittent follow-up with the institutions would have ensured that
they knew their responsibilities. Additionally, this would have allowed partici-
pants to have questions answered that they may have had about the system. At
the time this system was operating, LPZ did not have the resources to provide
follow-up contact to submitting institutions. However, in the future, this will
be an important aspect of a successful surveillance system.
5.4. USDA APHIS AZA Management Guidelines
for Avian Influenza: Zoological Parks
and Exhibitors Surveillance Plan
5.4.1 infectious agent
Originally isolated in Hong Kong in 1999, highly pathogenic H5N1 avian
influenza virus (HPAI H5N1) has since spread to 63 countries in Asia, Africa,
and Europe. It is of concern because of its extremely high mortality rate in
domesticated birds—mostly, chickens, ducks, and turkeys—and its ability
to cause fatal infections in humans. As of August 2009, there have been 438
human cases of HPAI H5N1, 262 of which have resulted in death, represent-
ing a mortality rate of nearly 60% (WHO 2009). Though the highly pathogenic
 
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