Human papillomavirus, seen in a coloured transmission electron micrograph.
PASIEKA/SPL/GETTY
On a sunny day in 1998, Maura Gillison was walking across the campus of Johns Hopkins University in Baltimore, Maryland, thinking about a virus. The young oncologist bumped into the director of the university's cancer centre, who asked politely about her work. Gillison described her discovery of early evidence that human papillomavirus (HPV) — a ubiquitous pathogen that infects nearly every human at some point in their lives — could be causing tens of thousands of cases of throat cancer each year in the United States. The senior doctor stared down at Gillison, not saying a word. “That was the first clue that what I was doing was interesting to others and had potential significance,” recalls Gillison. 
Only in 2005 did Gillison finally sit down with a doctoral student to analyse the data. Within an hour, the fruits of those years of labour popped up on the computer screen: people with head and neck cancer were 15 times more likely to be infected with HPV in their mouths or throats than those without1. The association backed up some of Gillison's earlier work, which showed2 how HPV DNA integrates itself into the nuclei of throat cells and produces cancer-causing proteins. Gillison leapt from her chair and began jumping up and down. “The association was so incredibly strong, it made me realize this was absolutely irrefutable evidence,” she says.
Since then, she and a network of other researchers have amassed a mountain of evidence that HPV causes a large proportion of head and neck cancers, and that these HPV-positive cancers are on the rise. The finding has been “a paradigm-shifting realization in the field”, says Robert Ferris, chief of the division of head and neck surgery at the University of Pittsburgh Cancer Institute in Pennsylvania.