Chickenpox (Varicella)د. وجدان اكرم
Chickenpox is a very contagious disease with secondary household attack rates of >90 percent in susceptible individuals, caused by the varicella-zoster virus a member of Herpes virus group. Humans are the only source of infection for this virus .The virus spreads easily from people with chickenpox to others who have never had the disease or received the chickenpox vaccine. The virus spreads in the air when an infected person coughs or sneezes. It can also be spread by touching or breathing in the virus particles that come from chickenpox blisters. The incubation period for varicella is 10–21 days, most commonly 14–16 days.
Period of communicability:
As long as 5 days, but usually 1-2 days before onset of rash and continuing until all lesions are crusted( usually about 5 days). Contagiousness may be prolonged in patients with altered immunity. Patients with herpes zoster may be infectious for a week or after the appearance of vesiculopustular lesions.
Immunity following varicella infection is considered to be long-lasting and second cases of varicella are thought to be rare. However, second cases may occur more commonly among immunocompetent persons than previously consideredImmunity following varicella infection is considered to be long-lasting and second cases of varicella are thought to be rare. However, second cases may occur more commonly among immunocompetent persons than previously considered
It causes a blister-like rash, itching, tiredness, and fever. The rash appears first on the trunk and face and can spread over the entire body causing between 250 and 500 itchy blisters.
Varicella-zoster virus (VZV) is one of eight herpes viruses known to cause human infection and is distributed worldwide. VZV infection causes two clinically distinct forms of disease: varicella (chickenpox) and herpes zoster (shingles). Primary VZV infection results in the diffuse vesicular rash of varicella, or chickenpox. Endogenous reactivation of latent VZV typically results in a localized skin infection known as herpes zoster, or shingles.
Primary varicella infection in children is generally a mild disease compared to more severe presentations in adults or immunocompromised patients of any age. The rates of infection, hospitalizations, and mortality have all declined in the US since the introduction of the varicella vaccine in 1995; immunization is recommended in all children before the age of five years and in nonimmune adults.
EPIDEMIOLOGY OF VARICELLA PRIOR TO VACCINE
Incidence of varicella — Varicella occurs throughout the year in temperate regions, but the incidence typically peaks in the months of March through May. According to national seroprevalence data from the prevaccine era, greater than 95 percent of persons in the United States acquired varicella before 20 years of age, and fewer than 2 percent of adults were susceptible to infection .Prior to 1995 the Centers for Disease Control and Prevention (CDC) estimated the yearly incidence of chickenpox in the United States at approximately four million cases, with nearly 11,000 admissions and 100 deaths.
Signs & Symptoms
Chickenpox most commonly causes an illness that lasts about 5-10 days.
The classic symptom of chickenpox is a rash that turns into itchy, fluid-filled blisters that eventually turn into scabs. The rash may first show up on the face, chest, and back then spread to the rest of the body, including inside the mouth, eyelids, or genital area. It usually takes about one week for all the blisters to become scabs.
Other typical symptoms that may begin to appear 1-2 days before rash include:
high fever
tiredness
loss of appetite
headache
Children usually miss 5 to 6 days of school or childcare due to their chickenpox.
Vaccinated Persons
Some people who have been vaccinated against chickenpox can still get the disease. However, the symptoms are usually milder with fewer blisters and mild or no fever. About 25% to 30% of vaccinated people who get chickenpox will develop illness as serious as chickenpox in unvaccinated persons.
Complications
Complications from chickenpox can occur, but they are not as common in otherwise healthy people who get the disease.
People who may have more severe symptoms and may be at high risk for complications include
Infants
Adolescents
Adults
Pregnant women
People with weakened immune systems because of illness or medications; for example,
People with HIV/AIDS or cancer
Patients who have had transplants, and
People on chemotherapy, immunosuppressive medications, or long-term use of steroids..
Serious complications from chickenpox include
dehydration
pneumonia
bleeding problems
infection or inflammation of the brain (encephalitis, cerebellar ataxia)
bacterial infections of the skin and soft tissues in children including Group A streptococcal infections
blood stream infections (sepsis)
toxic shock syndrome
bone infections
joint infections
Some people with serious complications from chickenpox can become so sick that they need to be hospitalized. Chickenpox can also cause death.
Some deaths from chickenpox continue to occur in healthy, unvaccinated children and adults. Many of the healthy adults who died from chickenpox contracted the disease from their unvaccinated children.
Prevention
The best way to prevent chickenpox is to get the chickenpox vaccine. Children, adolescents, and adults should have two doses of chickenpox vaccine.
Chickenpox vaccine is very safe and effective at preventing the disease. Most people who get the vaccine will not get chickenpox. If a vaccinated person does get chickenpox, it is usually mild—with fewer blisters and mild or no fever. The chickenpox vaccine prevents almost all cases of severe disease.
Vaccination:
Chickenpox vaccine is very effective at preventing chickenpox. About 80 to 90 percent of people who get vaccinated with one dose of chickenpox vaccine are protected from chickenpox. It is expected that an even higher proportion of those who get a second dose of chickenpox vaccine will be protected from chickenpox.
CDC recommends two doses of chickenpox vaccine for children, adolescents, and adults. Children should receive two doses of the vaccine—the first dose at 12 through 15 months old and a second dose at 4 through 6 years old. People who previously had one dose should talk with their health care provider about getting a second dose.
Some people who have been vaccinated against chickenpox can still get the disease. However, it is usually milder with fewer blisters and little or no fever.
Varicilla zoster Ig given 96 hours after exposure to prevent serious course.
Control measures:
Report to local health authority
Isolation : exclude children from school(after the vesicle dry and crusted usually 5 days in non immunized children and 1-4 days in immunized .
Concurrent disinfection.
Quarantine: usually none
Investigation of contact and source of infection.
Specific treatment : antiviral therapy.