Our Vaccine Update feature article “Fast Facts” series continues this month with a focus on chickenpox. With sporadic cases of this vaccine-preventable disease popping up in day cares and clinics, healthcare providers can brush up on information and resources related to this infection.
Chickenpox is highly contagious; it is caused by varicella-zoster virus (VZV). The infection spreads easily from person to person through respiratory droplets or direct contact with fluid from skin blisters. While many used to think of chickenpox as a “rite of passage,” it can cause serious complications — especially in vulnerable populations.
Before the vaccine was licensed in 1995, chickenpox was nearly universal in childhood. Each year, about 4 million people in the U.S. were infected, leading to approximately 10,000 hospitalizations and 100 to 150 deaths. Since widespread vaccination began, chickenpox cases, hospitalizations and deaths have all dramatically decreased, with fewer than 150,000 cases each year and fewer than 30 deaths annually in the U.S. However, when vaccination coverage wanes, outbreaks can reemerge — especially in schools and communities with low vaccine uptake.
Two doses of varicella vaccine are highly effective, providing close to 98% protection against any infection and nearly 100% protection against severe disease.
Recognizing chickenpox
Chickenpox typically begins with a mild fever and lack of energy, followed by the development of an itchy rash consisting of fluid-filled pustules on a red base. Because of this appearance, the rash is often described as “dewdrops on a rose petal.” In children, the rash may be the first sign of chickenpox. The blisters first appear on the face, chest and back and then spread outward to the limbs. The hallmark rash progresses in “crops” over several days, with lesions in different stages of development. This cropping marks an important clinical difference from many other rashes with fluid-filled blisters, like smallpox or mpox, in which all vesicles are at the same state of development.
The rash is characterized by severe itchiness and may number from a few spots to over 500 spots. Vaccinated people with “breakthrough” chickenpox, meaning an infection with the wild-type varicella-zoster virus, typically experience milder symptoms with fewer lesions and little or no fever. Notably, in breakthrough cases, the rash does not look like classic chickenpox lesions. Instead, the breakthrough rash typically consists of fewer than 50 blisters, which may not be fluid-filled blisters at all, but rather atypical flat lesions, as shown on this CDC fact sheet. The characteristics of mild illness and atypical lesions can make diagnosis of breakthrough cases more challenging.
Importantly, chickenpox can be confused with several other skin conditions, including herpes simplex virus (HSV), impetigo and insect bites. When in doubt — particularly in cases with potential public health implications — contact your local public health department for assistance. Regardless of whether a regular or breakthrough case, patients are contagious from 1–2 days before the start of the rash until all lesions have crusted, which typically takes about 5–7 days. Also, as a reminder, healthcare providers are required to report cases of varicella to their local health department.
Making a chickenpox diagnosis
Most chickenpox cases are diagnosed clinically. However, if diagnosis is uncertain, such as in vaccinated individuals experiencing a breakthrough case with atypical lesions, laboratory testing can help. Confirmation through testing can also help for counseling others who may have been exposed, particularly if exposures occurred in school or medical settings. PCR testing of lesion fluid or crusts is the most sensitive method. Serologic testing (IgM/IgG) has only limited use. IgM, which is classically considered a marker of acute infection, actually rises in both an acute varicella infection and during reactivation as shingles, so it cannot help confirm a person’s first infection. Two measurements of IgG over time may help identify a new varicella infection if IgG levels increase; however, this strategy requires two blood draws (and two visits), so it should be reserved for use only when PCR is not available.
Treatment and management of chickenpox
In healthy children, chickenpox will typically resolve on its own, but supportive care can help make patients more comfortable:
- Fever control with acetaminophen (avoid aspirin due to risk of Reye’s syndrome)
- Topical anti-itch lotions or oral antihistamines
- Adequate hydration and rest
Antiviral treatment (acyclovir) is recommended for specific groups:
- Unvaccinated individuals older than 12 years
- People with chronic skin or lung disease
- Those taking aspirin or corticosteroids for other conditions
- Immune-compromised individuals (should receive intravenous acyclovir)
- Pregnant people exposed or infected, after consulting with their OB-GYN
Most often, severe outcomes from chickenpox result from complications, so patients should be monitored for such. Those most likely to experience complications include adolescents, adults, pregnant people and immune-compromised individuals. Complications can include:
- Secondary bacterial infections of the skin, including cellulitis and necrotizing fasciitis
- Pneumonia (more common in adults)
- Encephalitis (swelling of the brain) or neurologic or muscular difficulties, such as lack of balance or coordination, slurred speech and tremors, among others. These effects typically result from swelling of the cerebellum.
- Sepsis
- Birth defects (following infection during pregnancy)
- Guillain-Barré syndrome
- Low platelets and bleeding complications
- Inflammation of the heart, kidneys, testes, liver or eyes
- Hospitalization or death
Long-term impact
After initial infection, varicella-zoster virus remains in the body, living in nerve cells. As such, it can later reactivate as shingles (herpes zoster), often with increasing age or during periods of immune suppression. The varicella vaccine reduces the risk and severity of shingles compared to natural infection, although a separate shingles vaccine is recommended for adults over 50 years of age.
Infection control: Reducing the spread of chickenpox
Chickenpox is highly contagious, particularly in close-contact settings, like schools, day cares and healthcare facilities. If 100 people are in a room together for several hours and one of them has chickenpox and the other 99 are susceptible to chickenpox, about 85 of the remaining 99 will get chickenpox.
Protecting patients
Patients suspected of having chickenpox should be isolated immediately so that other people in the healthcare setting are not exposed. If the family calls ahead with concerning symptoms, they should be directed to avoid common waiting rooms and be seen in a private room or designated isolation area.
Ideally, use airborne and contact precautions, particularly in healthcare settings. Patients should remain isolated at home until all lesions have crusted (typically 5–7 days after rash onset).
Unlike chickenpox, shingles (zoster) is not contagious, with one exception. If someone susceptible to chickenpox comes into contact with the shingles rash, they could develop chickenpox. As such, people with shingles can typically continue with their day-to-day activities and just keep the healing blisters covered, particularly if they will be around infants or others at risk for chickenpox.
Protecting staff
Healthcare workers should have documented varicella immunity, either through vaccination or previous infection. Personal protective equipment, including an N95 mask, is recommended when caring for suspected or confirmed cases.
Post-exposure measures
For susceptible individuals exposed to chickenpox, the following steps are recommended:
- If an individual is identified within 3-5 days of exposure, receipt of varicella vaccine may prevent or modify disease.
- If an individual is high risk for complications (e.g., immune compromised, pregnant, newborns with a mom infected around time of delivery, and in some cases, infants born prematurely) and they are identified within 10 days of exposure, receipt of varicella-zoster immune globulin (VariZIG) is recommended. Details can be found in Morbidity and Mortality Weekly Report’s “Updated Recommendations for Use of VariZIG — United States, 2013.”
Public health officials can assist with access to VariZIG and guidance for post-exposure isolation and monitoring.
Chickenpox: Key clinical takeaways
While chickenpox is currently uncommon, becoming familiar with its presentation and risks will help with prompt diagnosis and testing. Recognizing the itchy, “dewdrops on rose petals” rash, as well as having a high index of suspicion for atypical cases is key to limiting spread.
Resources for families
- Chickenpox: What You Should Know (Q&A)
- Varicella (Chickenpox): The Disease and Vaccines (webpage)
- Parents PACK Personal Stories - Chickenpox (webpage)
- MMR and chickenpox vaccines: Together or separate? (video)
- Vaccines on the Go: What You Should Know (mobile app)
- Rashes: What You Should Know (booklet)
Resources for providers
- Manual for the Surveillance of Vaccine-Preventable Diseases — Chapter 17: Varicella (webpage)
- Infection Control in Healthcare Personnel: Epidemiology and Control of Selected Infections — Varicella-Zoster Virus
Contributed by: Lori Handy, MD, MSCE , Charlotte A. Moser, MS, Paul A. Offit, MD
Our Vaccine Update feature article “Fast Facts” series continues this month with a focus on chickenpox. With sporadic cases of this vaccine-preventable disease popping up in day cares and clinics, healthcare providers can brush up on information and resources related to this infection.
Chickenpox is highly contagious; it is caused by varicella-zoster virus (VZV). The infection spreads easily from person to person through respiratory droplets or direct contact with fluid from skin blisters. While many used to think of chickenpox as a “rite of passage,” it can cause serious complications — especially in vulnerable populations.
Before the vaccine was licensed in 1995, chickenpox was nearly universal in childhood. Each year, about 4 million people in the U.S. were infected, leading to approximately 10,000 hospitalizations and 100 to 150 deaths. Since widespread vaccination began, chickenpox cases, hospitalizations and deaths have all dramatically decreased, with fewer than 150,000 cases each year and fewer than 30 deaths annually in the U.S. However, when vaccination coverage wanes, outbreaks can reemerge — especially in schools and communities with low vaccine uptake.
Two doses of varicella vaccine are highly effective, providing close to 98% protection against any infection and nearly 100% protection against severe disease.
Recognizing chickenpox
Chickenpox typically begins with a mild fever and lack of energy, followed by the development of an itchy rash consisting of fluid-filled pustules on a red base. Because of this appearance, the rash is often described as “dewdrops on a rose petal.” In children, the rash may be the first sign of chickenpox. The blisters first appear on the face, chest and back and then spread outward to the limbs. The hallmark rash progresses in “crops” over several days, with lesions in different stages of development. This cropping marks an important clinical difference from many other rashes with fluid-filled blisters, like smallpox or mpox, in which all vesicles are at the same state of development.
The rash is characterized by severe itchiness and may number from a few spots to over 500 spots. Vaccinated people with “breakthrough” chickenpox, meaning an infection with the wild-type varicella-zoster virus, typically experience milder symptoms with fewer lesions and little or no fever. Notably, in breakthrough cases, the rash does not look like classic chickenpox lesions. Instead, the breakthrough rash typically consists of fewer than 50 blisters, which may not be fluid-filled blisters at all, but rather atypical flat lesions, as shown on this CDC fact sheet. The characteristics of mild illness and atypical lesions can make diagnosis of breakthrough cases more challenging.
Importantly, chickenpox can be confused with several other skin conditions, including herpes simplex virus (HSV), impetigo and insect bites. When in doubt — particularly in cases with potential public health implications — contact your local public health department for assistance. Regardless of whether a regular or breakthrough case, patients are contagious from 1–2 days before the start of the rash until all lesions have crusted, which typically takes about 5–7 days. Also, as a reminder, healthcare providers are required to report cases of varicella to their local health department.
Making a chickenpox diagnosis
Most chickenpox cases are diagnosed clinically. However, if diagnosis is uncertain, such as in vaccinated individuals experiencing a breakthrough case with atypical lesions, laboratory testing can help. Confirmation through testing can also help for counseling others who may have been exposed, particularly if exposures occurred in school or medical settings. PCR testing of lesion fluid or crusts is the most sensitive method. Serologic testing (IgM/IgG) has only limited use. IgM, which is classically considered a marker of acute infection, actually rises in both an acute varicella infection and during reactivation as shingles, so it cannot help confirm a person’s first infection. Two measurements of IgG over time may help identify a new varicella infection if IgG levels increase; however, this strategy requires two blood draws (and two visits), so it should be reserved for use only when PCR is not available.
Treatment and management of chickenpox
In healthy children, chickenpox will typically resolve on its own, but supportive care can help make patients more comfortable:
- Fever control with acetaminophen (avoid aspirin due to risk of Reye’s syndrome)
- Topical anti-itch lotions or oral antihistamines
- Adequate hydration and rest
Antiviral treatment (acyclovir) is recommended for specific groups:
- Unvaccinated individuals older than 12 years
- People with chronic skin or lung disease
- Those taking aspirin or corticosteroids for other conditions
- Immune-compromised individuals (should receive intravenous acyclovir)
- Pregnant people exposed or infected, after consulting with their OB-GYN
Most often, severe outcomes from chickenpox result from complications, so patients should be monitored for such. Those most likely to experience complications include adolescents, adults, pregnant people and immune-compromised individuals. Complications can include:
- Secondary bacterial infections of the skin, including cellulitis and necrotizing fasciitis
- Pneumonia (more common in adults)
- Encephalitis (swelling of the brain) or neurologic or muscular difficulties, such as lack of balance or coordination, slurred speech and tremors, among others. These effects typically result from swelling of the cerebellum.
- Sepsis
- Birth defects (following infection during pregnancy)
- Guillain-Barré syndrome
- Low platelets and bleeding complications
- Inflammation of the heart, kidneys, testes, liver or eyes
- Hospitalization or death
Long-term impact
After initial infection, varicella-zoster virus remains in the body, living in nerve cells. As such, it can later reactivate as shingles (herpes zoster), often with increasing age or during periods of immune suppression. The varicella vaccine reduces the risk and severity of shingles compared to natural infection, although a separate shingles vaccine is recommended for adults over 50 years of age.
Infection control: Reducing the spread of chickenpox
Chickenpox is highly contagious, particularly in close-contact settings, like schools, day cares and healthcare facilities. If 100 people are in a room together for several hours and one of them has chickenpox and the other 99 are susceptible to chickenpox, about 85 of the remaining 99 will get chickenpox.
Protecting patients
Patients suspected of having chickenpox should be isolated immediately so that other people in the healthcare setting are not exposed. If the family calls ahead with concerning symptoms, they should be directed to avoid common waiting rooms and be seen in a private room or designated isolation area.
Ideally, use airborne and contact precautions, particularly in healthcare settings. Patients should remain isolated at home until all lesions have crusted (typically 5–7 days after rash onset).
Unlike chickenpox, shingles (zoster) is not contagious, with one exception. If someone susceptible to chickenpox comes into contact with the shingles rash, they could develop chickenpox. As such, people with shingles can typically continue with their day-to-day activities and just keep the healing blisters covered, particularly if they will be around infants or others at risk for chickenpox.
Protecting staff
Healthcare workers should have documented varicella immunity, either through vaccination or previous infection. Personal protective equipment, including an N95 mask, is recommended when caring for suspected or confirmed cases.
Post-exposure measures
For susceptible individuals exposed to chickenpox, the following steps are recommended:
- If an individual is identified within 3-5 days of exposure, receipt of varicella vaccine may prevent or modify disease.
- If an individual is high risk for complications (e.g., immune compromised, pregnant, newborns with a mom infected around time of delivery, and in some cases, infants born prematurely) and they are identified within 10 days of exposure, receipt of varicella-zoster immune globulin (VariZIG) is recommended. Details can be found in Morbidity and Mortality Weekly Report’s “Updated Recommendations for Use of VariZIG — United States, 2013.”
Public health officials can assist with access to VariZIG and guidance for post-exposure isolation and monitoring.
Chickenpox: Key clinical takeaways
While chickenpox is currently uncommon, becoming familiar with its presentation and risks will help with prompt diagnosis and testing. Recognizing the itchy, “dewdrops on rose petals” rash, as well as having a high index of suspicion for atypical cases is key to limiting spread.
Resources for families
- Chickenpox: What You Should Know (Q&A)
- Varicella (Chickenpox): The Disease and Vaccines (webpage)
- Parents PACK Personal Stories - Chickenpox (webpage)
- MMR and chickenpox vaccines: Together or separate? (video)
- Vaccines on the Go: What You Should Know (mobile app)
- Rashes: What You Should Know (booklet)
Resources for providers
- Manual for the Surveillance of Vaccine-Preventable Diseases — Chapter 17: Varicella (webpage)
- Infection Control in Healthcare Personnel: Epidemiology and Control of Selected Infections — Varicella-Zoster Virus
Contributed by: Lori Handy, MD, MSCE , Charlotte A. Moser, MS, Paul A. Offit, MD