In "Spiral", the curse is explained in detail, and is discovered to be a virus. When someone watches the cursed tape (or something else carrying the curse) some of their DNA is changed to become that of the Ring Virus (a hybrid of Sadako's DNA and that of the smallpox virus). This travels throughout their body and in most cases causes a sarcoma to form on one of the arteries of their heart. If the curse has not been appeased within seven days, the sarcoma detaches from the artery and clogs it, causing heart failure. Eventually, however, the virus is able to infect people through means other than videotapes, such as a report detailing the events of "Ring" written by Kazuyuki Asakawa in which the virus had entered from Asakawa's body, a novel version of the report published by Asakawa's brother, a movie based on the novel (which Sadako was cast as herself in), and finally the Metastatic Human Cancer virus that appears in the third novel, "Loop".