It is believed that their strong electric charges attract them either to the viruses (thus inactivating them) or to the cells of the vaginal wall (thus covering those cells like acoatofpaint and preventing viruses from entering the body).
When I arrive, the walls are being given a fresh coatofpaint in preparation for next week's fiesta - a party in celebration of the village's patron saint, during which the 40-odd inhabitants gather to sing, dance and roast a pig on a spit.