The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From University of Nebraska - Lincoln:
The Curse of the Tree-Man HD is a narrated interactive comic that tells the story of how HPV attacks the body and creates a runaway infection. This is the story of Dede, and Indonesian fisherman, the HPV virus that turns him into The Terrible Tree-Man, and an American doctor who discovers the cause of Dede's illness.Explore the Attack of the P-virus - the cause of warts - to learn more about warts, interact with videos of the real Dr. Anthony Gaspari and learn how he helped Dede, and peer deep into the HPV virus itself. All in The Curse of the Tree-Man HD, from The World of Viruses!Learn more about The World of Viruses and our collection of other iOS Games and Apps at http://www.worldofviruses.unl.edu.