Björk continues to roll out Biophilia with today's release of the "Virus" single through One Little Indian/Nonesuch Records, and as a special feature on the Biophilia App for iPad, iPhone, and iPod touch, available through In-App Purchase. Both are available exclusively on the iTunes Store and the App Store. "The more we get to hear from Björk’s Biophilia," says OneThirtyBPM after listening to the "sublime" new song, "the more it seems like the best album ever."

“Virus” is an original song and new feature of the Biophilia App that explores the relationship between biological virus as part musical instrument, part sonic artwork, and part scientifically informed educational animation. It may be played in song-mode to watch the life cycle of a virus or played in instrument-mode to create music. In “Virus,” infectious agents attack a central cell. Biological and musical processes unite as with each stage of the virus’s life cycle a new song section is heard. The app feature starts with a large cell surrounded by others floating on screen. Small viruses appear, latch on to the cell, and inject their DNA. The strands amass and penetrate the large cell’s nucleus, then the viruses replicate. The song is complete once the cell is destroyed. The user may watch the animation of the song to see and hear the viruses multiply or touch the viruses, flick the nuclei in the cells, play sounds from the song and create original music.

SPIN calls "Virus" the album's "most intimate song yet," adding that "never has a song about human ailment sounded so seductive or beautiful." Paste says: "It’s simple yet beautiful, showing off the singer’s vocal range as she belts over the gentle twang of bells."

In addition to the song, the “Virus” feature includes the linear animation of the virus life-cycle, the musical instrument, an animation of the music, scrolling notation that can be used karaoke-style, and a written analysis by Sheffield University’s Nicola Dibben that explores Björk’s inspirations for “Virus.”

“Virus” was created by Björk in collaboration with interactive artist and app developer Scott Snibbe. “Virus” is also available as a single, exclusively on iTunes. Snibbe spoke with the CBC about the project in an article available at cbc.ca.

Biophilia is Björk’s most interdisciplinary project to date, comprising a studio album, an app, a new website, custom-made musical instruments, live shows, and educational workshops. The complete Biophilia album is due worldwide on September 27. Björk recently completed her residency at this year’s Manchester International Festival where Biophilia received its world premiere. She will return to the UK to headline Bestival on September 11 before taking the Biophilia show to Iceland, where she undertakes a residency of eight shows at the brand new Harpa Concert Hall, including two nights as part of the Iceland Airwaves Festival starting October 12.

Björk is featured on yesterday's episode of The Strand, the arts program from the BBC World Service, on which she discusses Biophilia, how the advent of the iPad impacted her music writing and her perception of the project, and what inspired the album's subject matter. Listen to the episode at bbc.co.uk.

The four physical versions of the Biophilia album—on CD, vinyl, and two custom-made editions—may be pre-ordered in the Nonesuch Store. This is the final week to order the two custom-made editions: the Biophilia Manual, which presents the music on two CDs in a 48-page cloth-bound, thread-sewn hardback book, and the Ultimate Edition, which includes the Manual along with 10 tuning forks, each representing the tone of a track on the album. They must be ordered by the end of the day this Thursday, August 11.

Björk has collaborated with app developers, scientists, writers, inventors, musicians, and instrument makers to create a unique multimedia exploration of the universe and its physical forces—particularly those where music, nature and technology meet. The project is inspired by and explores these relationships between musical structures and natural phenomena, from the atomic to the cosmic.