"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 map publication.

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, Yahoo, MSN...):

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 the maps is not available for release by USGS. USGS obtains the data from CDC. CDC, in turn, obtains the data from state health departments that have agreed with CDC on public dissemination of that data in certain forums: USGS maps, the Morbidity and Mortality Weekly Report (MMWR), the CDC web site, and select scientific publications.

Maps of WNV activity in previous years are available by clicking the link to Historical Data.

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.