Primary varicella occurs in all countries worldwide. In 2015<unk>  resulted in 6,400 deaths globally – down from 8,900 in 1990. There were 7,000 deaths in 2013. In temperate countries,<unk>  is primarily a disease of children, with most cases occurring during the winter and spring, most likely due to school contact. It is one of the classic diseases of childhood, with most cases occurring in children up to age 15. Varicella is highly transmissible, with an infection rate of 90% in close contacts. In temperate countries, most people become infected before adulthood, and 10% of young adults remain susceptible. In the tropics,<unk>  often occurs in older people and may cause more serious disease. In adults, the pock marks are darker and the scars more prominent than in children. In the United States, the Centers for Disease Control and Prevention (CDC) does not require state health departments to report infections of<unk> , and only 31 states currently volunteer this information. However, in a 2013 study conducted by the social media disease surveillance tool called Sickweather, anecdotal reports of<unk>  infections on Facebook and Twitter were used to measure and rank states with the most infections per capita, with Maryland, Tennessee and Illinois in the top three.
Chickenpox
Monkeypox
Sealpox
Smallpox
Cowpox
Stevens–Johnson syndrome
Toxic epidermal necrolysis
Mumps