chickenpox chickenpox chickenpox, or chicken pox, also known as varicella, is a highly contagious disease caused by the initial infection with varicella zoster virus (vzv), a member of the herpesvirus family. the disease results in a characteristic skin rash that forms small, itchy blisters, which eventually scab over. it usually starts on the chest, back, and face. it then spreads to the rest of the body. the rash and other symptoms, such as fever, tiredness, and headaches, usually last five to seven days. complications may occasionally include pneumonia, inflammation of the brain, and bacterial skin infections. the disease is usually more severe in adults than in children. chickenpoxother namesvaricellaa boy presenting with the characteristic blisters of chickenpoxspecialtyinfectious diseasesymptomssmall, itchy blisters, headache, loss of appetite, tiredness, feverusual onset10–21 days after exposureduration5–10 dayscausesvaricella zoster viruspreventionvaricella vaccinemedicationcalamine lotion, paracetamol (acetaminophen), aciclovirdeaths6,400 per year (with shingles) chickenpox is an airborne disease which easily spreads via human-to-human transmission, typically through the coughs and sneezes of an infected person. the incubation period is 10–21 days, after which the characteristic rash appears. it may be spread from one to two days before the rash appears until all lesions have crusted over. it may also spread through contact with the blisters. those with shingles may spread chickenpox to those who are not immune through contact with the blisters. the disease can usually be diagnosed based on the presenting symptom; however, in unusual cases it may be confirmed by polymerase chain reaction (pcr) testing of the blister fluid or scabs. testing for antibodies may be done to determine if a person is immune. people usually only get chickenpox once. although reinfections by the virus occur, these reinfections usually do not cause any symptoms. since its introduction in 1995, the varicella vaccine has resulted in a decrease in the number of cases and complications from the disease. it protects about 70–90 percent of people from disease with a greater benefit for severe disease. routine immunization of children is recommended in many countries. immunization within three days of exposure may improve outcomes in children. 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. for those at increased risk of complications, antiviral medication such as aciclovir are recommended. chickenpox occurs in all parts of the world. in 2013 there were 140 million cases of chickenpox and shingles worldwide. before routine immunization the number of cases occurring each year was similar to the number of people born. since immunization the number of infections in the united states has decreased nearly 90%. in 2015 chickenpox resulted in 6,400 deaths globally – down from 8,900 in 1990. death occurs in about 1 per 60,000 cases. chickenpox was not separated from smallpox until the late 19th century. in 1888 its connection to shingles was determined. the first documented use of the term chicken pox was in 1658. various explanations have been suggested for the use of "chicken" in the name, one being the relative mildness of the disease. signs and symptoms a single blister, typical during the early stages of the rash the early (prodromal) symptoms in adolescents and adults are nausea, loss of appetite, aching muscles, and headache. this is followed by the characteristic rash or oral sores, malaise, and a low-grade fever that signal the presence of the disease. oral manifestations of the disease (enanthem) not uncommonly may precede the external rash (exanthem). in children the illness is not usually preceded by prodromal symptoms, and the first sign is the rash or the spots in the oral cavity. the rash begins as small red dots on the face, scalp, torso, upper arms and legs; progressing over 10–12 hours to small bumps, blisters and pustules; followed by umbilication and the formation of scabs. at the blister stage, intense itching is usually present. blisters may also occur on the palms, soles, and genital area. commonly, visible evidence of the disease develops in the oral cavity and tonsil areas in the form of small ulcers which can be painful or itchy or both; this enanthem (internal rash) can precede the exanthem (external rash) by 1 to 3 days or can be concurrent. these symptoms of chickenpox appear 10 to 21 days after exposure to a contagious person. adults may have a more widespread rash and longer fever, and they are more likely to experience complications, such as varicella pneumonia. because watery nasal discharge containing live virus usually precedes both exanthem (external rash) and enanthem (oral ulcers) by 1 to 2 days, the infected person actually becomes contagious one to two days before recognition of the disease. 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. the condition usually resolves by itself within a week or two. the rash may, however, last for up to one month. chickenpox is rarely fatal, although it is generally more severe in adult men than in women or children. non-immune pregnant women and those with a suppressed immune system are at highest risk of serious complications. arterial ischemic stroke (ais) associated with chickenpox in the previous year accounts for nearly one third of childhood ais. the most common late complication of chickenpox is shingles (herpes zoster), caused by reactivation of the varicella zoster virus decades after the initial, often childhood, chickenpox infection. the back of a 30-year-old male after five days of the rash a 3-year-old girl with a chickenpox rash on her torso lower leg of a child with chickenpox a child with chickenpox a child with chickenpox on her face. a child with chickenpox chickenpox blister closeup, day 7 after start of fever pregnancy and neonates during pregnancy the dangers to the fetus associated with a primary vzv infection are greater in the first six months. in the third trimester, the mother is more likely to have severe symptoms. for pregnant women, antibodies produced as a result of immunization or previous infection are transferred via the placenta to the fetus. varicella infection in pregnant women could lead to spread via the placenta and infection of the fetus. if infection occurs during the first 28 weeks of gestation, this can lead to fetal varicella syndrome (also known as congenital varicella syndrome). effects on the fetus can range in severity from underdeveloped toes and fingers to severe anal and bladder malformation. possible problems include: damage to brain: encephalitis, microcephaly, hydrocephaly, aplasia of brain damage to the eye: optic stalk, optic cup, and lens vesicles, microphthalmia, cataracts, chorioretinitis, optic atrophy other neurological disorder: damage to cervical and lumbosacral spinal cord, motor/sensory deficits, absent deep tendon reflexes, anisocoria/horner's syndrome damage to body: hypoplasia of upper/lower extremities, anal and bladder sphincter dysfunction skin disorders: (cicatricial) skin lesions, hypopigmentation infection late in gestation or immediately following birth is referred to as "neonatal varicella". maternal infection is associated with premature delivery. the risk of the baby developing the disease is greatest following exposure to infection in the period 7 days before delivery and up to 8 days following the birth. the baby may also be exposed to the virus via infectious siblings or other contacts, but this is of less concern if the mother is immune. newborns who develop symptoms are at a high risk of pneumonia and other serious complications of the disease. pathophysiology main article: varicella zoster virus exposure to vzv in a healthy child initiates the production of host immunoglobulin g (igg), immunoglobulin m (igm), and immunoglobulin a (iga) antibodies; igg antibodies persist for life and confer immunity. cell-mediated immune responses are also important in limiting the scope and the duration of primary varicella infection. after primary infection, vzv is hypothesized to spread from mucosal and epidermal lesions to local sensory nerves. vzv then remains latent in the dorsal ganglion cells of the sensory nerves. reactivation of vzv results in the clinically distinct syndrome of herpes zoster (i.e., shingles), postherpetic neuralgia, and sometimes ramsay hunt syndrome type ii. varicella zoster can affect the arteries in the neck and head, producing stroke, either during childhood, or after a latency period of many years. shingles main article: herpes zoster after a chickenpox infection, the virus remains dormant in the body's nerve tissues for about 50 years. this, however, does not mean that vzv cannot be contracted later in life. the immune system usually keeps the virus at bay, however it can still manifest itself at any given age between 1 and 60, causing a different form of the viral infection called shingles (also known as herpes zoster). since the human immune system efficacy decreases with age, the united states advisory committee on immunization practices (acip) suggests that every adult over the age of 50 years get the herpes zoster vaccine. shingles affects one in five adults infected with chickenpox as children, especially those who are immune-suppressed, particularly from cancer, hiv, or other conditions. stress can bring on shingles as well, although scientists are still researching the connection. adults over the age of 60 who had chickenpox but not shingles are the most prone age demographic. diagnosis chickenpox the diagnosis of chickenpox is primarily based on the signs and symptoms, with typical early symptoms followed by a characteristic rash. 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. vesicular fluid can be examined with a tzanck smear, or by testing for direct fluorescent antibody. the fluid can also be "cultured", whereby attempts are made to grow the virus from a fluid sample. blood tests can be used to identify a response to acute infection (igm) or previous infection and subsequent immunity (igg). prenatal diagnosis of fetal varicella infection can be performed using ultrasound, though a delay of 5 weeks following primary maternal infection is advised. a pcr (dna) test of the mother's amniotic fluid can also be performed, though the risk of spontaneous abortion due to the amniocentesis procedure is higher than the risk of the baby's developing fetal varicella syndrome. prevention hygiene measures the spread of chickenpox can be prevented by isolating affected individuals. contagion is by exposure to respiratory droplets, or direct contact with lesions, within a period lasting from three days before the onset of the rash, to four days after the onset of the rash. the chickenpox virus is susceptible to disinfectants, notably chlorine bleach (i.e., sodium hypochlorite). like all enveloped viruses, it is sensitive to drying, heat and detergents. vaccine main article: varicella vaccine chickenpox can be prevented by vaccination. the side effects are usually mild, such as some pain or swelling at the injection site. a live attenuated varicella vaccine, the oka strain, was developed by michiaki takahashi and his colleagues in japan in the early 1970s. in 1995, merck & co. licensed the "oka" strain of the varicella virus in the united states, and maurice hilleman's team at merck invented a varicella vaccine in the same year. the varicella vaccine is recommended in many countries. some countries require the varicella vaccination or an exemption before entering elementary school. a second dose is recommended five years after the initial immunization. a vaccinated person is likely to have a milder case of chickenpox if they become infected. immunization within three days following household contact reduces infection rates and severity in children. being exposed to chickenpox as an adult (for example, through contact with infected children) may boost immunity to shingles. so it was thought, that when the majority of children are vaccinated against chickenpox, adults might lose this natural boosting, so immunity would drop and more shingles cases would occur. 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. it is part of the routine immunization schedule in the us. some european countries include it as part of universal vaccinations in children, but not all countries provide the vaccine. in the uk as of 2014, the vaccine is only recommended in people