This image is taken from the Public Health Image Library (PHIL), a division of the CDC. The description of the image specifically states that it is in the public domain: "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." It is credited to Michael Smith. I downloaded the high-resolution TIFF from the website and re-saved it in the PNG format (compression level 9) using GIMP. This reduced the file size by about half while resulting in no loss of visual information. Original URL: [1]. Due to the extensive use of server-side scripting on the PHIL website, it is impossible to link directly to the image description page, but it can easily be located by going to this search page and entering the image ID (8133) in the search box.

Cette image est l’œuvre des Centers for Disease Control and Prevention , division du Département de la Santé et des Services Sociaux des États-Unis, réalisée par un employé dans le cadre de ses activités professionnelles. En tant qu'œuvre du gouvernement fédéral des États-Unis d'Amérique, cette image est placée dans le domaine public.