Chickenpox

Chickenpox or chicken pox is a highly contagious illness caused by primary infection with varicella zoster virus (VZV). It usually starts with vesicular skin rash mainly on the body and head rather than at the periphery and become itchy, raw pockmarks, which mostly heal without scarring.

Chicken pox is spread easily through coughs or sneezes of ill individuals or through direct contact with secretions from the rash. Following primary infection there is usually lifelong protective immunity from further episodes of chickenpox.

Chickenpox is rarely fatal, although it is generally more severe in adult males than in adult females or children. Pregnant women and those with a suppressed immune system are at highest risk of serious complications. Chicken pox is now believed to be the cause of one third of stroke cases in children. The most common late complication of chicken pox is shingles, caused by reactivation of the varicella zoster virus decades after the initial episode of chickenpox.

Chickenpox has been observed in other primates, including chimpanzees and gorillas.

Signs and symptoms
Chickenpox is a highly infectious disease that spreads from person to person by direct contact or by air from an infected person's coughing or sneezing. Touching the fluid blister can also spread the disease. A person with chickenpox is infectious from one to five days before the rash appears. The contagious period continues until all blisters have formed scabs, which may take 5 to 6 days at which point they are no longer contagious. It takes from 10 to 21 days after contact with an infected person for someone to develop chickenpox. Chickenpox (varicella) is often heralded by a prodrome of anorexia, myalgia, nausea, fever, headache, sore throat, pain in both ears, complaints of pressure in head or swollen face, and malaise in adolescents and adults, while in children the first symptom is usually the development of a papular rash, followed by development of malaise, fever (a body temperature of 38 C, but may be as high as 42 C in rare cases), and anorexia. Rarely cough, rhinitis, abdominal pain, and gastrointestinal distress has been reported in patients with varicella. Typically, the disease is more severe in adults.

Diagnosis
The diagnosis of varicella is primarily clinical, with typical early "prodromal" symptoms, and then the characteristic rash. Confirmation of the diagnosis can be sought through either 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 Tsanck smear, or better with examination 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 developing foetal varicella syndrome.

Epidemiology
Primary varicella is an endemic disease. Cases of varicella are seen throughout the year but more commonly in winter and early spring. Varicella is one of the classic diseases of childhood, with the highest prevalence in the 4–10 year old age group. Like rubella, it is uncommon in preschool children. Varicella is highly communicable, with an infection rate of 90% in close contacts. Most people become infected before adulthood but 10% of young adults remain susceptible.

Historically, varicella has been a disease predominantly affecting preschool and school-aged children. In adults the pock marks are darker and the scars more prominent than in children.

Pathophysiology
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), and sometimes Ramsay Hunt syndrome type II.

Infection in pregnancy and neonates
For pregnant women, antibodies produced as a result of immunization or previous infection are transferred via the placenta to the fetus. Women who are immune to chickenpox cannot become infected and do not need to be concerned about it for themselves or their infant during pregnancy.

Varicella infection in pregnant women can lead to viral transmission 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 cap, 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 prior to delivery and up to 7 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.

Shingles
After a chickenpox infection, the virus remains dormant in the body's nerve tissues. The immune system keeps the virus at bay, but later in life, usually as an adult, it can be reactivated and cause a different form of the virus called shingles.

Hygiene measures
The spread of chicken pox 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 prior to the onset of the rash, to four days after the onset of the rash. Therefore, avoidance of close proximity or physical contact with affected individuals during that period will prevent contagion. The chicken pox virus (VZV) is susceptible to disinfectants, notably chlorine bleach (i.e., sodium hypochlorite). Also, like all enveloped viruses, VZV is sensitive to desiccation, heat and detergents. Therefore these viruses are relatively easy to kill.

Vaccine
A varicella vaccine was first developed by Michiaki Takahashi in 1974 derived from the Oka strain. It has been available in the U.S. since 1995 to inoculate against the disease. Some countries require the varicella vaccination or an exemption before entering elementary school. Protection is not lifelong and further vaccination is necessary five years after the initial immunization. The chickenpox vaccine is not part of the routine childhood vaccination schedule in the UK. In the UK, the vaccine is currently only offered to people who are particularly vulnerable to chickenpox.

Treatment
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. It is important to maintain good hygiene and daily cleaning of skin with warm water to avoid secondary bacterial infection. Scratching may also increase the risk of secondary infection. Addition of a small quantity of vinegar to the water is sometimes advocated. Painkillers could be taken to prevent feeling itchy

To relieve the symptoms of chicken pox, people commonly use anti-itching creams and lotions. These lotions are not to be used on the face or close to the eyes. An oatmeal bath also might help ease discomfort.

Varicella treatment mainly consists of easing the symptoms as there is no actual cure of the condition. Some treatments are however available for relieving the symptoms while the immune system clears the virus from the body. As a protective measure, patients are usually required to stay at home while they are infectious to avoid spreading the disease to others. Also, sufferers are frequently asked to cut their nails short or to wear gloves to prevent scratching and to minimize the risk of secondary infections.

The condition resolves by itself within a couple of weeks but meanwhile patients must pay attention to their personal hygiene. The rash caused by varicella zoster virus may however last for up to one month, although the infectious stage does not take longer than a week or two. Also, staying in a cold surrounding can help in easing the itching as heat and sweat makes it worse. Calamine lotion may be tried as it may relieve the symptoms because of its soothing, cooling effect on the skin.

Natural chicken pox remedies include pea water, baking soda, vitamin E oil, honey, herbal tea or carrot and coriander. It is believed that the irritation of the skin can be relieved to some extent with water in which fresh peas have been cooked. A lotion made of baking soda with water can be sponged onto the skin of the patients to ease the itching. Also, rubbing vitamin E oil or honey on the skin is thought to have a healing effect on the marks that could remain after the infection has been cured. Some people claim that the mild sedative effect of green tea is effective in relieving the symptoms. It is not however known to what extent these home remedies can actually help the patients cope better with their symptoms.

A varicella vaccine is available for people who have been exposed to the virus, but have not experienced symptoms. The vaccine is more effective if administered within three days and up to five days after exposure. It has been shown that the chicken pox vaccine may prevent or reduce the symptoms in 90% of cases, if given within three days after exposure. People who have been exposed to the virus but who are contraindicated to receive the vaccine, there is a medication available, called varicella zoster immunoglobulin or VZIG which may prevent or reduce the symptoms after exposure. VZIG is primarily administered to individuals who are at risk of developing complications due to its high costs and temporary protection. This type of treatment is only recommended in newborns whose mothers have had chicken pox few days prior or after delivery, children with leukemia or lymphoma, people with a poor immune system or pregnant women. VZIG is recommended to be administered no later than 96 hours after exposure to the virus.

Children
If oral acyclovir is started within 24 hours of rash onset it decreases symptoms by one day but has no effect on complication rates. Use of acyclovir therefore is not currently recommended for immunocompetent individuals (i.e., otherwise healthy persons without known immunodeficiency or those on immunosuppressive medication).

Treatment of chicken pox in children is aimed at symptoms whilst the immune system deals with the virus. With children younger than 12 years cutting nails and keeping them clean is an important part of treatment as they are more likely to deep scratch their blisters. Children younger than 12 years old and older than one month are not meant to receive antiviral medication if they are not suffering from another medical condition which would put them at risk of developing complications.

Increased amounts of water are recommended to avoid dehydration, especially if the child develops fever. Fever, headaches or pain can be relieved with painkillers such as ibuprofen or paracetamol. Children who are older than one year may be administered antihistamine tablets or liquid medicines which are helpful in cases when the child is not able to sleep because of the itching.

Acyclovir or immunoglobulin is generally prescribed in children who are at risk of complications from chicken pox. They receive the same treatment as the one mentioned above plus antiviral medication additionally. The category of children that are considered at risk to develop complications includes infants less than one month old, those with a suppressed immune system, those who are taking steroids or immune suppressing medication or children with severe heart, lung and skin conditions. Moreover, adults and teenagers are considered at risk of complications and they are normally administered antiviral medication.

Aspirin is highly contraindicated in children younger than 16 years as it has been related with a potentially fatal condition known as Reye's syndrome.

Adults
Infection in otherwise healthy adults tends to be more severe and active; treatment with antiviral drugs (e.g. acyclovir) is generally advised, as long as it is started within 24–48 hours from rash onset.

Remedies to ease the symptoms of chicken pox in adults are basically the same as those used on children. Moreover, adults are often prescribed antiviral medication as it is effective in reducing the severity of the condition and the likelihood of developing complications. Antiviral medicines are not however aimed to kill the virus, but to stop it from multiplying.

Adults are also advised to increase the water intake to reduce dehydration and to relieve headaches. Painkillers such as paracetamol and ibuprofen are also recommended as they are effective in relieving itching and other symptoms such as fever or pains. Antihistamines may be used in cases when the symptoms cause the inability to sleep, as they are efficient for easing the itching and they are acting 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 poor immune system.

Sorivudine, a nucleoside analogue has been found in few case reports effective in the treatment of primary varicella in healthy adults. Larger scale clinical trials are needed to demonstrate the efficacy of this medication.

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 5th day. Chickenpox infection is milder in young children, and symptomatic treatment, with sodium bicarbonate baths or antihistamine medication may ease itching. Paracetamol (acetaminophen) is widely used to reduce fever. Aspirin, or products containing aspirin, must not be given to children with chickenpox as this risks causing Reye's Syndrome.

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, 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, or encephalitis, can occur in immunocompromised individuals, although the risk is higher with herpes zoster. Necrotizing fasciitis is also a rare complication.

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 also 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 etiology of these hemorrhagic chickenpox syndromes is not known.

History


Chickenpox was first identified by Persian scientist Muhammad ibn Zakariya ar-Razi (865–925), known to the West as "Rhazes", who clearly distinguished it from smallpox and measles. Giovanni Filippo (1510–1580) of Palermo later provided a more detailed description of varicella (chickenpox).