who are particularly vulnerable to chickenpox. this is to keep the virus in circulation thereby exposing the population to the virus at an early age, when it is less harmful, and to reduce the occurrence of shingles in those who have already had chickenpox by repeated exposure to the virus later in life. in populations that have not been immunized or if immunity is questionable, a clinician may order an enzyme immunoassay. an immunoassay measures the levels of antibodies against the virus that give immunity to a person. if the levels of antibodies are low (low titer) or questionable, reimmunization may be done. treatment treatment mainly consists of easing the symptoms. as a protective measure, people are usually required to stay at home while they are infectious to avoid spreading the disease to others. cutting the fingernails short or wearing gloves may prevent scratching and minimize the risk of secondary infections. although there have been no formal clinical studies evaluating the effectiveness of topical application of calamine lotion (a topical barrier preparation containing zinc oxide, and one of the most commonly used interventions), it has an excellent safety profile. maintaining good hygiene and daily cleaning of skin with warm water can help to avoid secondary bacterial infection; scratching may increase the risk of secondary infection. paracetamol (acetaminophen) but not aspirin may be used to reduce fever. aspirin use by someone with chickenpox may cause serious, sometimes fatal disease of the liver and brain, reye syndrome. people at risk of developing severe complications who have had significant exposure to the virus may be given intra-muscular varicella zoster immune globulin (vzig), a preparation containing high titres of antibodies to varicella zoster virus, to ward off the disease. antivirals are sometimes used. children if aciclovir by mouth is started within 24 hours of rash onset, it decreases symptoms by one day but has no effect on complication rates. use of aciclovir therefore is not currently recommended for individuals with normal immune function. children younger than 12 years old and older than one month are not meant to receive antiviral drugs unless they have another medical condition which puts them at risk of developing complications. treatment of chickenpox in children is aimed at symptoms while the immune system deals with the virus. with children younger than 12 years, cutting fingernails and keeping them clean is an important part of treatment as they are more likely to scratch their blisters more deeply than adults. aspirin is highly contraindicated in children younger than 16 years, as it has been related to reye syndrome. adults infection in otherwise healthy adults tends to be more severe. treatment with antiviral drugs (e.g. aciclovir or valaciclovir) is generally advised, as long as it is started within 24–48 hours from rash onset. remedies to ease the symptoms of chickenpox in adults are basically the same as those used for children. adults are more often prescribed antiviral medication, as it is effective in reducing the severity of the condition and the likelihood of developing complications. adults are advised to increase water intake to reduce dehydration and to relieve headaches. painkillers such as paracetamol (acetaminophen) are recommended, as they are effective in relieving itching and other symptoms such as fever or pains. antihistamines relieve itching and may be used in cases where the itching prevents sleep, because they also act as a sedative. as with children, antiviral medication is considered more useful for those adults who are more prone to develop complications. these include pregnant women or people who have a weakened immune system. prognosis the duration of the visible blistering caused by varicella zoster virus varies in children usually from 4 to 7 days, and the appearance of new blisters begins to subside after the fifth day. chickenpox infection is milder in young children, and symptomatic treatment, with sodium bicarbonate baths or antihistamine medication may ease itching. in adults, the disease is more severe, though the incidence is much less common. infection in adults is associated with greater morbidity and mortality due to pneumonia (either direct viral pneumonia or secondary bacterial pneumonia), bronchitis (either viral bronchitis or secondary bacterial bronchitis), hepatitis, and encephalitis. in particular, up to 10% of pregnant women with chickenpox develop pneumonia, the severity of which increases with onset later in gestation. in england and wales, 75% of deaths due to chickenpox are in adults. inflammation of the brain, encephalitis, can occur in immunocompromised individuals, although the risk is higher with herpes zoster. necrotizing fasciitis is also a rare complication. varicella can be lethal to individuals with impaired immunity. the number of people in this high-risk group has increased, due to the hiv epidemic and the increased use of immunosuppressive therapies. varicella is a particular problem in hospitals when there are patients with immune systems weakened by drugs (e.g., high-dose steroids) or hiv. secondary bacterial infection of skin lesions, manifesting as impetigo, cellulitis, and erysipelas, is the most common complication in healthy children. disseminated primary varicella infection usually seen in the immunocompromised may have high morbidity. ninety percent of cases of varicella pneumonia occur in the adult population. rarer complications of disseminated chickenpox include myocarditis, hepatitis, and glomerulonephritis. hemorrhagic complications are more common in the immunocompromised or immunosuppressed populations, although healthy children and adults have been affected. five major clinical syndromes have been described: febrile purpura, malignant chickenpox with purpura, postinfectious purpura, purpura fulminans, and anaphylactoid purpura. these syndromes have variable courses, with febrile purpura being the most benign of the syndromes and having an uncomplicated outcome. in contrast, malignant chickenpox with purpura is a grave clinical condition that has a mortality rate of greater than 70%. the cause of these hemorrhagic chickenpox syndromes is not known. epidemiology primary varicella occurs in all countries worldwide. in 2015 chickenpox resulted in 6,400 deaths globally – down from 8,900 in 1990. there were 7,000 deaths in 2013. varicella is highly transmissible, with an infection rate of 90% in close contacts. in temperate countries, chickenpox is primarily a disease of children, with most cases occurring during the winter and spring, most likely due to school contact. in such countries it is one of the classic diseases of childhood, with most cases occurring in children up to age 15; most people become infected before adulthood, and 10% of young adults remain susceptible. in the united states, a temperate country, the centers for disease control and prevention (cdc) do not require state health departments to report infections of chickenpox, and only 31 states volunteered this information as of 2013. a 2013 study conducted by the social media disease surveillance tool called sickweather used anecdotal reports of chickenpox infections on social media systems facebook and twitter to measure and rank states with the most infections per capita, with maryland, tennessee and illinois in the top three. in the tropics, chickenpox 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. society and culture etymology how the term chickenpox originated is not clear but it may be due to it being a relatively mild disease. it has been said to be derived from chickpeas, based on resemblance of the vesicles to chickpeas, or to come from the rash resembling chicken pecks. other suggestions include the designation chicken for a child (i.e., literally 'child pox'), a corruption of itching-pox, or the idea that the disease may have originated in chickens. samuel johnson explained the designation as "from its being of no very great danger". intentional exposure because chickenpox is usually more severe in adults than it is in children, some parents deliberately expose their children to the virus, for example by taking them to "chickenpox parties". doctors say that children are safer getting the vaccine, which is a weakened form of the virus, than getting the disease, which can be fatal or lead to shingles later in life. repeated exposure to chickenpox may protect against zoster. other animals humans are the only known species that the disease affects naturally. however, chickenpox has been caused in other primates, including chimpanzees and gorillas. research sorivudine, a nucleoside analog, has been reported to be effective in the treatment of primary varicella in healthy adults (case reports only), but large-scale clinical trials are still needed to demonstrate its efficacy. there was speculation in 2005 that continuous dosing of aciclovir by mouth for a period of time could eradicate vzv from the host, although further trials were required to discern whether eradication was actually viable.