Molluscum contagiosum virus (MCV) is a double-stranded DNA virus and member of the poxvirus family. MCV is in a different genus (Molluscipoxvirus) than the orthopoxviruses (variola, vaccinia, and monkeypox viruses).
Four major genotypes of molluscum contagiosum virus have been identified, with MCV1 and MCV2 as the most common genotypes. MCV causes a chronic, localized infection with small papules on the skin called molluscum. Similar to the virus that causes smallpox, the only known host for MCV is humans.
Information about MCV at the molecular level has been hampered by the inability to grow the virus in standard cell culture or in an animal model of infection. While there are reports of some success in growth using human foreskin xenograft fragments, a major advance in understanding the biology of the virus came when the entire 190,000 base pair genome of the MCV was sequenced.
Like the variola (smallpox) virus, MCV replicates in the cytoplasm of cells, and more than one-half of the MCV genes are similar to those found in variola and vaccinia viruses. Molluscum contagiosum contains many unique genes that encode proteins responsible for novel viral defense mechanisms; these mechanisms inhibit the host inflammatory and immune responses to the infection.
Epidemiology of the Molluscum Contagiosum Virus:
Molluscum contagiosum virus (MCV) infection has been reported worldwide. Although four distinct genotypes have been identified, genotype 1 (MCV1) predominates and represents 90 percent of cases in the United States. A population-based Australian seroepidemiology study in 357 people revealed an overall seropositivity rate of 23 percent. The data also indicated that very mild or subclinical cases may be more common in the general community than previously suspected.
It is estimated that fewer than 5 percent of children in the United States have clinical evidence of MCV infection. The number of cases in adults has varied over time.
Molluscum contagiosum is common enough that you should not be surprised if you see someone with it (child’s classmate, neighbor child) or if someone in your family becomes infected. Although not limited to children, it is most common in children 1 to 10 years of age. In addition, there is evidence that molluscum infections have been on the rise in the United States since 1966