The fundamental cause of chickenpox is the varicella-zoster virus (VZV), a highly contagious DNA virus belonging to the herpesvirus family. Its method of attack is systematic. The virus first enters a new host through the respiratory tract (via inhaled droplets from a cough or sneeze) or contact with blister fluid. It then begins to replicate in the lymph nodes of the neck. After about 4-6 days, it enters the bloodstream (primary viremia), spreading to organs like the liver and spleen, where it multiplies further. A second, larger wave of virus then enters the bloodstream (secondary viremia), finally traveling to and infecting the skin cells, which results in the widespread, itchy rash we recognize as chickenpox.
Regarding the timeline, the incubation period is typically 10 to 21 days. This means after your children were exposed at the playground, you should monitor them for symptoms for the next two to three weeks. The most common time for the rash to appear is about two weeks (14-16 days) after exposure. A person becomes contagious from 1-2 days before the rash appears until all blisters have crusted over.