Infectious diseases


Last update: 15-01-2024

How else can it be called?

  • Varicella

  • Chicken pox

  • ICD-10: B01

What is chickenpox?

Chickenpox is a highly contagious disease caused by the varicella-zoster virus (VZV), which is the same virus that causes shingles (herpes zoster) in adults.

Chickenpox is one of the most common childhood viral exanthems.

The initial infection of chickenpox tends to be more frequent during the first ten years of life, while reactivation as herpes zoster typically occurs in individuals aged 65 and above.

Varicella-zoster virus susceptibility is limited to just 10% of individuals aged 15 and above.

What is the incidence of chickenpox?

The varicella zoster virus (VZV) commonly infects young children, reaching its peak incidence between 2 and 8 years of age, typically occurring well before the age of 14.

Epidemics follow cycles of 3-4 years, particularly from January to May. Adults can only contract the infection if they have not had chickenpox previously.

What are the main symptoms of chickenpox?

The incubation period for the varicella virus, marked by the absence of symptoms, is about two weeks. Initial symptoms include an abrupt onset of fever and feelings of fatigue and weakness.

Then, a rash of vesicles (exanthem) emerges on the body and the face, continuing to erupt for three or four days, spreading across the entire body, and eventually transitioning to desiccation, forming a crust before naturally falling off.

How is chickenpox spread to one person to another?

Chickenpox is spread through direct contact with the chickenpox rash before crusting, as the fluid in the vesicles contains high concentrations of the virus. It is also transmitted through the air via respiratory secretions from an infected person.

The most contagious period is one or two days before the rash appears, and up to five days after the vesicles first appear.

How many times can you catch the chickenpox?

Once. Chickenpox generally results in lifelong immunity.

Nevertheless, the virus can remain latent in the body within the nerve ganglia, reactivating years later as herpes zoster (a painful vesicular rash occurring in adults, and occasionally in children) particularly when Symptoms the body's natural defenses are weakened for some reason.

Which is the recommended treatment?

In healthy children, chickenpox is a mild illness and the treatment is aimed at reducing itching and discomfort. Children with chickenpox should not be given aspirin due to the possibility of causing a very rare complication called Reye’s syndrome.

However, in some cases, treatment with acyclovir (an antiviral medication) may be necessary within the first 24 hours after the onset of the rash, as it reduces the time of appearance of new lesions, the total number of lesions, the duration of fever, and the number of hypopigmented lesions.

Although all children with chickenpox can be treated with acyclovir, the American Academy of Pediatrics suggests preferentially treating those who are at higher risk of acquiring severe chickenpox or developing a complication (and does not recommend treating them all, since there is no need to treat forget that any treatment can present unwanted effects). It is recommended for:

  • Adolescents over 12 years old.
  • Children with chronic skin or lung conditions.
  • Children receiving chronic aspirin therapy.
  • Children receiving oral or inhaled corticosteroids.

Newborns whose mothers had chickenpox during the five days before delivery and two days after delivery should receive intravenous acyclovir if they contract chickenpox, due to the high rate of morbidity and mortality reported.

For immunocompromised patients (individuals with compromised natural immune defenses) and cases involving visceral complications (such as pneumonia, nephritis, encephalitis, etc.), the intravenous route is the preferred method of administration.

Every individual aged 12 and above, diagnosed with chickenpox, should be administered acyclovir, given the elevated risk of complications, visceral dissemination, and mortality. Pregnant women should undergo treatment, as they face an increased risk of visceral dissemination throughout the entire duration of their pregnancy.

What are the complications of chickenpox?

Infections are the most frequent complication. The most common is bacterial superinfection of the lesions, caused by S. aureus and S. pyogenes. Other infections are less common.

Neurological complications represent the second most frequent reason for hospitalization, particularly among healthy children, especially those under 5 years old and those over 20 years old.

Pneumonitis caused by chickenpox occurs most frequently in adults and immunocompromised hosts.

People with weakened immune systems, either due to inherent deficiencies or as a result of medications suppressing their immune response (such as cancer chemotherapy or chronic high-dose corticosteroids), are at high risk of developing severe forms of chickenpox, including complications like pneumonia.

If a woman contracts chickenpox during pregnancy, she faces an elevated risk of lung infection. There is also a risk of transmitting the virus to the fetus. If this happens within the first twenty weeks, it can lead to fetal death or result in malformations, including scarring and alterations in the size of the head and limbs.

Perinatal chickenpox in a baby carries a mortality rate of up to 30% when the infection occurs between the five days before delivery and the two days after delivery, as the baby does not receive antibodies from the mother.

Hepatitis caused by the varicella virus is also common, though it rarely manifests symptoms and is typically detected through laboratory analysis.

Other possible complications of chickenpox are: myocarditis, nephritis, arthritis, corneal injuries and glomerulonephritis.

Nevertheless, serious complications are uncommon in children in general.

How can avoid getting chickenpox?

Children diagnosed with chickenpox should remain at home for five days after the onset of the rash or until the lesions crust over (occasionally, isolation may be extended up to 10 days). It is crucial to take extra precautions to prevent contact with chickenpox, especially in immunocompromised individuals.

Isolating the affected individual, using a mask, and handwashing are essential.

Moreover, there is an available varicella vaccine administered in two doses for children and individuals at risk

What if you have been exposed to chickenpox?

Post-exposure, varicella-zoster immune globulin can be administered within 96 hours of contact, with the maximum effectiveness observed when given within the initial 48 hours of exposure.

Varicella-zoster immune globulin is indicated after significant exposure to chickenpox in the following situations:

  • Immunocompromised host.
  • Susceptible pregnant woman with less than 20 weeks of gestation.
  • Newborn whose mother had chickenpox within 5 days before delivery and 2 days postpartum.
  • Premature newborn over 28 weeks of gestation, hospitalized, with a mother has not had chickenpox or is seronegative.
  • Premature newborn under 28 weeks of gestation, hospitalized, regardless of maternal history of chickenpox.

Vaccination can also be administered following a potential exposure; the chickenpox vaccine is between 79% and 100% effective in preventing severe chickenpox when given within 72 hours of contact with chickenpox or zoster.

The American Academy of Pediatrics recommends vaccinating susceptible children within 72 hours following exposure.

Doctors should warn parents and patients that vaccine administration may not provide complete protection, and that children may still develop the disease.

Finally, it has been proven that acyclovir is effective in preventing chickenpox when administered to susceptible patients during the second half of the incubation period (from day 7 to 14 after exposure).

Medically reviewed by Yolanda Patricia Gómez González Ph.D. on 15-01-2024


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