"Sentinel" refers to cases where an
animal (most often a chicken, but horses as well) is kept in a known
location (e.g. chicken coop) and their blood is routinely sampled
(usually every week or two) and tested for the presence of WNV. If
the test is positive, that is considered a case (even though the
animal may not have any symptoms) and is an indication that virus
is circulating in the area.
"Veterinary" refers to WNV clinical
cases found in non-human mammals. Most often (99.9% of the time)
this means cases in horses. However a few cases have been reported
in dogs, bears, bats, etc. thus the broader label.
We are aware of recent "reported" cases in the news
media, however, the maps on our web site are based on the official
data from the CDC. We receive official updates from the CDC at 3
A.M. every Tuesday morning (during peak-season we also receive updates
every Friday morning). We then update our 260+ web pages
typically well before noon on the same day we receive the updates.
Media reports are sometimes based on "probable" diagnoses
that may later be found to be incorrect. The data we use to make
the maps have been approved for publication by the state health
departments, assembled by the CDC, and then released to us for
Please do not report dead birds directly to
this web site or the CDC. Instead, contact your local government's
department of health which you can find by searching the following
keywords at your favorite internet search web site (e.g. Google,
report dead birds west nile virus [county name] [state name]
Simply type all of the keywords above (seperated by a space) in the search engine.
The maps are in the public domain and may be reproduced in any form
without obtaining formal release or permission.
We would appreciate citing USGS as the source.
The data used to create these maps are not available for release by the
US Geological Survey (USGS) . USGS obtains the data regarding arboviral
cases through an agreement with the Centers for Disease Control and
Prevention (CDC). Arboviral data are reported to CDC by state and local
health departments which have allowed for public dissemination of the data
in certain forums such as: USGS disease maps, the Morbidity and Mortality
Weekly Report (MMWR), the CDC web site, and selected scientific publications.
If you are interested in access to arboviral data for the US it is possible
to petition CDC, please send an e-mail to firstname.lastname@example.org requesting an
arboviral data request form.
Maps of WNV activity in previous years are available by clicking the link to
The WNV surveillance data is constantly being revised, corrected, and updated.
For this and technical reasons, we do not have an archive of prior weekly
maps available for viewing.