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.

本图片是美国卫生及公共服务部旗下的美国疾病控制与预防中心的作品，系有关雇员作为其公务目的所拍摄或制作。作为美国联邦政府的作品，本图片属于公有领域。