Molluscum contagiosum is caused by a virus that is a member of the pox virus family. Pox viruses are notorious for their ability to evade the host's immune system by both active and passive mechanisms. Since the eradication of smallpox, the only pox virus that naturally infects humans is molluscum contagiosum virus (MCV). MCV causes benign proliferative lesions of the skin in normal individuals. There are at least two types of MCV based on DNA restriction analysis. There does not appear to be any predilection for one virus type to infect certain groups of people, certain ages, or certain body areas. Both viruses seem to infect equally. A recent study demonstrated that one of the proteins coded by the MCV genome inhibits the body's lymphocytes and prevents inflammation. This is apparently why it takes so long for the body to rid itself of MCV.
Molluscum contagiosum (MCV) is a common infection throughout the United States. It accounts for approximately 1% of all diagnoses of skin disorders. The exact incidence in the United States is unknown. Higher incidence in children with eczema as well as in immunocompromised individuals has been documented. An Australian study found anti-MCV antibodies in 39% of adults older than 50 years, demonstrating exposure to be very common. There is no well-documented predilection for infection among any racial group. Studies do not demonstrate any definite difference in incidence between the sexes. Cell-mediated immunity is thought to be important in modulating and controlling the infection.