Madonna attends the opening ceremony of the Mercy James Children's Hospital at Queen Elizabeth Central Hospital in Blantyre, Malawi on July 11, 2017.

On World AIDS Day, and just before Britney Spears' birthday, Madonna shared an acoustic cover of "Toxic" on Instagram.

Guitar in hand, Madonna began with the In the Zone single's second verse in an infrared video: "It's getting late/ To give you up/ I took a sip/ From my devil's cup/ Slowly, it's taking over me."

"Silence =Death!" she wrote. "Song For World AIDS Day! #toxic# poisonparadise."

Madonna also wished Spears, who turned 36 on Dec. 2, a happy birthday while honoring the day that recognizes those who have battled HIV/AIDS.

In separate posts, she resurfaced a poignant letter that ran as an ad in Billboard magazine in 1991 and an old photograph with two friends who died of the disease. She added, "We need to continue to make people aware of this disease, to do what we can to facilitate research and above all to practice safe sex!!"

Watch her perform "Toxic" and see her letter below.