Keywords: Norovirus EM PHIL 2172 lores.jpg An electron micrograph of the Norovirus with 27-32nm-sized viral particles Norwalk viruses and related caliciviruses are important causes of nonbacterial gastroenteritis in the United States An estimated 181 000 cases of this type of food poisoning occur annually Content Providers s CDC Creation Date 1981 Copyright Restrictions None - This image is in the public domain and thus free of any copyright restrictions As a matter of courtesy we request that the content provider be credited and notified in any public or private usage of this image http //phil cdc gov/PHIL_Images/09192002/00012/PHIL_2172_lores jpg PD-USGov Norovirus |