Varicella Chickenpox is caused by Varicella zoster virus and is usually mild, but it may be severe in infants, adults and persons with impaired immune systems. Almost everyone gets chickenpox by adulthood (more than 95% of Americans). Chickenpox is highly contagious. CDC estimates that 4 million cases occur each year. For more detail and original CDC source click here: http://www.cdc.gov/od/oc/media/fact/chickenp.htm. Varicella Child with mild Chicken Pox Child with severe Chicken Pox Disclaimer: Recommendations are provided only as an assistance for educators and for physicians making clinical decisions regarding the care of their patients. As such, they cannot substitute for the individual judgment brought to each clinical situation by the patient’s physician. As with all clinical reference resources, they reflect the best understanding of the science of medicine at the time of publication, but they should be used with the clear understanding that continued research may result in new knowledge and recommendations. Links to organizations found at this site are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by the Society of Teachers of Family Medicine (STFM) or the Group on Immunization Education (GIE), and none should be inferred. The STFM and the GIE are not responsible for the content of the individual organization webpages found at these links. The Group on Immunization Education is responsible for the planning and administration of this web site. Web, Desktop & PDA Software Solutions and Services DanielWeaver.com