chickenpox is caused by the herpes zoster virus also known as the varicella zoster virus. it is spread by droplets from a sneeze or cough or by contact with the clothing bed linens or oozing vesicles of an infected person. the onset of symptoms is seven to 21 days after exposure. the disease is most contagious a day before the rash appears and up to seven days after or until the rash is completely dry and scabbed.
what causes chickenpox?