CERVICAL cancer is usually caused by a viral infection. Two
particular strains of the human papilloma virus (HPV) are
responsible for 70% of such cancers. They do so by turning off
genes that would otherwise suppress the formation of tumours.
HPV infections do not, however, necessarily lead to cervical
cancer—the best estimate is that less than 1% do. And a paper
just published in the Lancet Oncology by Xavier Castellsagué of
the Catalan Institute of Oncology, in L'Hospitalet de Llobregat,
Spain, and his colleagues suggests a way even that figure might
be reduced.  Dr Castellsagué was intrigued by evidence that
intrauterine devices (IUDs)—small, T-shaped gadgets that release
hormones or copper to prevent pregnancy—reduce the risk of
endometrial cancer. The devices' effects on cervical cancer have
been less clear. Indeed, since the 1930s, some researchers have
speculated that IUDs might actually increase the chance that
cancer will develop. Dr Castellsagué thought the matter worth
investigating.  He and his co