What Causes Molluscum Contagiosum?
Molluscum contagiosum is caused by the molluscum contagiosum virus (MCV), a poxvirus from the Molluscipoxvirus genus that exclusively infects human skin through direct contact with infected individuals or contaminated surfaces. 1, 2
Viral Etiology
MCV is a DNA poxvirus with exclusive tropism for human keratinocytes 2. The virus does not cause viremia and remains confined to the epidermis and subcutaneous tissue 2, 3. After an incubation period of 2-6 weeks, the virus causes breakdown of the skin barrier, resulting in the characteristic umbilicated papules 2.
Transmission Routes
The virus spreads through three primary mechanisms:
- Direct skin-to-skin contact with infected individuals (most common in children through play, sports, or close contact) 4, 3
- Sexual transmission in adults, particularly affecting genital areas 5, 6
- Autoinoculation from scratching or touching existing lesions and spreading to other body sites 4
- Fomite transmission through shared towels, swimming pools, bathtubs, and sports equipment 1, 3
High-Risk Populations
Certain groups face increased susceptibility:
- Children aged 0-16 years (5-11% prevalence), particularly school-aged children in day care or pool settings 1, 3
- Sexually active adults (genital transmission) 5, 6
- Immunocompromised individuals including HIV patients, organ transplant recipients, and those on immunosuppressive therapy develop more extensive, persistent lesions 7, 8
- Patients with atopic dermatitis experience more widespread lesions and complications 1, 3
Immune Evasion Mechanisms
MCV persists by producing at least 11 viral proteins that actively suppress host immunity 9. These proteins inhibit multiple immune pathways, dampening local inflammatory responses and allowing prolonged viral survival in the epidermis 9. This explains why infections can persist for months to years until the immune system eventually mounts a strong inflammatory response (the "beginning of the end" or BOTE phenomenon) 9.
Clinical Pitfall: The virus spreads easily in athletic settings, particularly among wrestlers and contact sport athletes, through skin-to-skin contact and contaminated mats 1. Prevention requires avoiding contact with visible lesions, not sharing towels or equipment, and proper disinfection of shared surfaces with diluted bleach solution 1.