Warts are caused by human papilloma virus (HPV). Although there are more than 150 strains of HPV, only a limited number cause warts.[1][2][3] HPV is spread through skin contact—either from body part to body part in the same individual, or from contact with other infected individuals. HPV can also spread by sharing objects that have come into contact with the virus, such as washcloths, towels, or clothing. Infections typically occur on areas of broken skin, where the skin barrier is compromised. Whether or not a wart will develop after exposure to HPV depends on the individual’s immune system, which may be able to fight off the HPV infection before a wart develops.