[3][7][5] The disease results in a characteristic skin rash that forms small, itchy blisters, which eventually scab over.

[9] Chickenpox is an airborne disease which easily spreads via human-to-human transmission, typically through the coughs and sneezes of an infected person.

[5] The disease can usually be diagnosed based on the presenting symptom;[10] however, in unusual cases it may be confirmed by polymerase chain reaction (PCR) testing of the blister fluid or scabs.

[11] Since its introduction in 1995 in the United States, the varicella vaccine has resulted in a decrease in the number of cases and complications from the disease.

[13] Treatment of those infected may include calamine lotion to help with itching, keeping the fingernails short to decrease injury from scratching, and the use of paracetamol (acetaminophen) to help with fevers.

[16] The early (prodromal) symptoms in adolescents and adults are nausea, loss of appetite, aching muscles, and headache.

Contagiousness persists until all vesicular lesions have become dry crusts (scabs), which usually entails four or five days, by which time nasal shedding of live virus ceases.

[medical citation needed][22] Chickenpox is rarely fatal, although it is generally more severe in adult men than in women or children.

[24] For pregnant women, antibodies produced as a result of immunization or previous infection are transferred via the placenta to the fetus.

After primary infection, VZV is hypothesized to spread from mucosal and epidermal lesions to local sensory nerves.

[32] Varicella zoster can affect the arteries in the neck and head, producing stroke, either during childhood, or after a latency period of many years.

The immune system usually keeps the virus at bay, but it can still manifest itself at any given age causing a different form of the viral infection called shingles (also known as herpes zoster).

Confirmation of the diagnosis is by examination of the fluid within the vesicles of the rash, or by testing blood for evidence of an acute immunologic response.

[2] A live attenuated varicella vaccine, the Oka strain, was developed by Michiaki Takahashi and his colleagues in Japan in the early 1970s.

Therefore, it was thought that when the majority of children were vaccinated against chickenpox, adults might lose this natural boost, so immunity would drop and more shingles cases would occur.

[47] On the other hand, current observations suggest that exposure to children with varicella is not a critical factor in the maintenance of immunity.

Multiple subclinical reactivations of varicella-zoster virus may occur spontaneously and, despite not causing clinical disease, may still provide an endogenous boost to immunity against zoster.

Cutting the fingernails short or wearing gloves may prevent scratching and minimize the risk of secondary infections.

[59][60] If aciclovir by mouth is started within 24 hours of rash onset, it decreases symptoms by one day but does not affect complication rates.

Children younger than 12 years old and older than one month are not meant to receive antiviral drugs unless they have another medical condition that puts them at risk of developing complications.

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.

[66] 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.

Adults are more often prescribed antiviral medication, as it is effective in reducing the severity of the condition and the likelihood of developing complications.

Chickenpox infection is milder in young children, and symptomatic treatment, with sodium bicarbonate baths or antihistamine medication may ease itching.

[74] Varicella is a particular problem in hospitals when there are patients with immune systems weakened by drugs (e.g., high-dose steroids) or HIV.

[75] Secondary bacterial infection of skin lesions, manifesting as impetigo, cellulitis, and erysipelas, is the most common complication in healthy children.

[77] 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;[78] most people become infected before adulthood, and 10% of young adults remain susceptible.

[79] 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.

[88] 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.