Chickenpox (varicella) is caused by varicella zoster virus (VZV), a type of herpes virus. It is often a mild illness, but may be severe in infants, pregnant women, adults and persons with weakened immune systems. The greatest number of chickenpox cases occurs in the late winter and spring.
Before the chickenpox vaccine, almost everyone got chickenpox by adulthood--more than 95% of American adults have already had chickenpox.
Symptoms
Chickenpox has a characteristic itchy rash that often starts on the trunk and face with pink spots and tiny fluid-filled blisters (“pox”) that then dry and become scabs in 4 to 5 days.
The rash may be the first sign of illness and sometimes occurs with fever and general fatigue.
An infected person may have anywhere from only a few pox to more than 500 (average 300400) pox on their body during the illness.
Chickenpox can sometimes have severe complications such as bacterial skin infections and pneumonia.
Some children who have been vaccinated against chickenpox can get a mild case of chickenpox with a small number of “spots” that may not go on to blister and crust.
How is it spread?
Chickenpox virus is highly contagious and is spread by direct contact with secretions (such as saliva) or pox from an infected individual, or by respiratory secretions released into the air from sneezing or coughing. The illness starts 10 to 21 days after contact with an infected person.
Infected persons are contagious from 1 to 2 days before the rash appears, until all the pox have formed scabs— usually 5 days from the time the pox appeared.
People with immune systems weakened by illness or drugs may require more time for their pox to scab over.
A person who has never had chickenpox or chickenpox vaccine has a 90% chance of becoming infected if exposed to a family member with chickenpox.
Diagnosis
Chickenpox is typically diagnosed by the symptoms and the characteristic appearance of the rash.
Occasionally a healthcare provider will use laboratory tests for chickenpox if the diagnosis is unclear or if the illness is severe.
Prevention
Vaccination is the best way to prevent chickenpox.
Two doses of varicella vaccine are recommended for children 12 months of age and older, adolescents, and adults if they have not had chickenpox.
All healthy children should routinely receive their first dose of vaccine at 12-15 months of age.
A second dose of vaccine is routinely recommended for all children 4-6 years of age.
Children 13 years and older and adults
who do not have evidence of prior immunity routinely receive 2 doses of vaccine 4 to 8 weeks apart.
Second dose catch-up vaccination is recommended for children, adolescents, and adults who previously received 1 dose. The doses should be at least 3 months apart for children 12 months to 12 years, and at least 4 weeks apart for individuals over 13 years of age.
The vaccine occasionally causes mild side effects including fever and a mild rash that can occur 5 to 26 days after immunization.
You don’t need the vaccine if you have already had chickenpox. If you are not sure whether you have had chickenpox, talk to your healthcare provider about getting a blood test.
Varicella vaccine is highly effective at preventing chickenpox, especially severe cases of the disease, and its complications.
What should I do if I've been exposed to chickenpox?
If you are already immune to chickenpox, you most likely won’t become sick. Most people do not get chickenpox more than once.
If you’re not already immune to chickenpox, varicella vaccine given within 3 days of exposure can possibly prevent chickenpox. Vaccination 3 to 5 days after exposure probably won’t prevent chickenpox but it may make it milder.
Persons at high risk for complications from chickenpox, such as immunocompromised persons, pregnant women, and premature infants, should contact their healthcare provider immediately.
What is "shingles"?
Shingles, also called herpes zoster or zoster, is a painful skin rash caused by the varicella zoster virus (VZV). After a person recovers from chickenpox, the virus stays in the body. Usually the virus does not cause any problems; however, the virus can reappear years later, causing shingles.
Shingles usually starts as a rash on one side of the face or body. The rash starts as blisters that scab after 3 to 5 days. The rash usually clears within 2 to 4 weeks. Before the rash develops, there is often pain, itching, or tingling in the area where the rash will develop. Other symptoms can include fever, headache, chills and upset stomach.
Direct contact with the blisters of a person with shingles can cause chickenpox in someone who has never had chickenpox and has not received the varicella vaccine.
A vaccine for shingles was licensed in 2006. In clinical trials, the vaccine prevented shingles in about half of people 60 years of age and older. It can also reduce the pain associated with shingles.
A single dose of shingles vaccine is indicated for adults 60 years of age and older.
Contact us
Report all King County cases to Public Health by calling 206-296-4774.
