system
Given the following post, respond as if you're commenting on Reddit:
human
Why do viruses, such as smallpox, chickenpox, and monkeypox, cause random lesions and blisters?

Viruses like smallpox lead to blisters, rashes, and or lesions on the surface of the skin. How does the virus cause this an why do the 'pox' tend to appear randomly on the body. What decides the location of these marks and their density or cluster formation?
gpt
For chicken pox, you inhale the varicella zoster virus, and it replicates in your lungs. As your body fights back, T cells come into the tissue and become infected by the virus. These T cells then get reprogrammed by the virus to traffick to hair follicles, where they cause secondary infection, and spread in the skin layers there, causing the "pox". So each pox was an infected T cell that found that specific spot. Incidentally the virus then infects the nerves that innervate this region, trafficks back to the ganglia, and goes latent for years to decades. It can then come back to that same patch of skin(dermatome) when it reactivates as shingles.