Warts, caused by the human papillomavirus virus, are contagious, according to KidsHealth. Once someone catches the virus, through contact with an infected person's wart, or a towel, surface or other object that came in contact with the wart, they can catch the human papillomavirus virus (HPV).
Once HPV is contracted, warts are then able to form on broken or irritated skin, according to KidsHealth. People who bite their fingernails or pick at their hangnails are more prone to develop warts, as they are more likely to have broken skin on their hands, giving the virus any easy entryway to invade the body. The amount of time it takes when someone contracts HPV and when they develop a wart varies.