Madonna shared a stirring cover of Britney Spears? ?Toxic? on Friday, December 1, in honor of Worlds AIDS Day. The legendary pop icon, 59, shared an infrared video of herself on Twitter singing the 2004 hit and playing the guitar, captioning it, ?Silence = Death. One wrote, ?Hey @ Madonna you?re little Twitter shows are awesome. The ?Vogue? singer appeared on Spears? 2003 album, In The Zone, for ?Me Against The Music,? where she joined the ??Baby One More Time? songstress in the music video.