TV producer and campaigner Hannah died after being diagnosed with breast cancer for the second time.
Comedian Rhod Gilbert was diagnosed with stage four head and neck cancer caused by contracting the HPV virus.
"She lives every day and she’s fighting,” the Buffy the Vampire Slayer star said in an interview published on Wednesday.
One in 10 men and half of women experience no symptoms.
The discovery could lead to a “whole new line of drug development”.