| disease | Chickenpox |
| alias | Varicella, Chickenpox |
Chickenpox (varicella) is an acute infectious disease caused by the varicella-zoster virus, characterized by mild systemic symptoms and the appearance of successive batches of macules, papules, vesicles, and crusts on the skin and mucous membranes. This disease is most commonly seen in children.
bubble_chart Epidemiology
(1) Source of Pestilence The patient is the only source of pestilence, which is contagious from 1-2 days before the onset of symptoms until the dryness and accumulation of scabs after the rash.
(2) Transmission Route It is primarily spread through droplets and contact with pestilence. The pestilence is highly contagious, with 80-90% of susceptible individuals falling ill after exposure in children's collective settings, necessitating strict isolation.
(3) Susceptibility Individuals of any age can be infected, with infants, young children, and preschool-aged children being more commonly affected. Infection is rare in infants under 6 months, but newborns can also contract the disease. When pregnant women suffer from chickenpox, the fetus may be infected or even develop congenital chickenpox syndrome. Adult cases are occasionally seen.
The disease can occur year-round but is more prevalent in winter and spring. After one infection, lasting immunity is usually acquired, and reinfection is extremely rare.
The pathogen is the chickenpox varicella-zoster virus (varicella-zoster virus, VZV), which belongs to the herpesvirus family and is a double-stranded DNA virus. It has a diameter of 150–200 nm and is an icosahedral virus with an envelope. This virus has weak viability in the external environment and can be inactivated by ether. The virus replicates in the nuclei of infected cells and is pathogenic only to humans. It is present in the vesicular fluid, blood, and oral secretions of infected patients, exhibiting strong pathogenicity. When inoculated into human embryonic amniotic membrane tissue cultures, it can produce specific cytopathic effects, forming eosinophilic inclusion bodies within the nuclei. The viral glycoproteins are divided into five categories (gpⅠ, gpⅡ, gpⅢ, gpⅣ, and gpⅤ), among which gpⅠ, gpⅡ, and gpⅢ antibodies have neutralizing effects against the virus. In recent years, further research on its serotypes, subtypes, and glycoproteins Ⅰ, Ⅱ, and Ⅲ antibodies has contributed to a better understanding of its immune functions.
bubble_chart Pathological ChangesThe virus initially replicates in the nasopharynx, then invades the bloodstream, possibly replicating in mononuclear phagocytes and spreading throughout the body. Therefore, viremia is the basis for systemic symptoms and skin-mucosal rashes. The lesions primarily occur in the spinous cell layer of the skin, showing degenerative changes and intracellular edema, forming ballooning cells with eosinophilic intranuclear inclusion bodies. The rupture of ballooning cells or multinucleated giant cells, along with the infiltration of tissue fluid, leads to the formation of vesicles. The dermis exhibits capillary dilation and mononuclear cell infiltration. Mucosal lesions resemble skin rashes, but the vesicles often rupture to form small ulcers. Additionally, autopsies of some fatal cases revealed small focal and nodular consolidation areas in various organs such as the esophagus, liver, pancreas, renal pelvis, ureter, bladder, and adrenal glands, accompanied by multiple hemorrhagic foci. Microscopically, the interstitial exudate in the lungs mainly consists of red blood cells, fibrin, and multinucleated giant cells containing eosinophilic bodies. Chickenpox encephalitis is similar to measles encephalitis and other post-infectious encephalitides, characterized by perivascular demyelination.
bubble_chart Clinical Manifestations
(1) The incubation period is 10 to 24 days, usually 13 to 17 days.
(2) Prodromal period: Adults may experience fever, headache, sore throat, limb pain, nausea, vomiting, and abdominal pain 1 to 2 days before the rash appears. In children, the rash and systemic symptoms often appear simultaneously, without prodromal symptoms.
Rashes are also commonly seen on mucous membranes such as the mouth, throat, or genitals. Early lesions appear as small red papules, quickly turning into vesicles and then rupturing to form small ulcers. Sometimes, similar rashes may appear on the conjunctiva or larynx.
The above describes typical chickenpox, where the rash is sparse and systemic symptoms are mild. In severe cases, the rash may cover the entire body, even affecting internal organs (such as the lungs), with more pronounced systemic symptoms, high fever, and prolonged fever duration. Adult chickenpox is often severe.
Atypical chickenpox is rare and may present in the following forms:
1. Hemorrhagic, progressive (lasting over 2 weeks), and disseminated chickenpox: Mainly seen in patients treated with corticosteroids or other immunosuppressive drugs. The vesicles contain bloody exudate, or petechiae and ecchymoses may appear on normal skin.
2. Congenital chickenpox syndrome and neonatal chickenpox: If the mother contracts chickenpox within 4 days before delivery, the newborn may develop symptoms 5 to 10 days after birth, often leading to disseminated chickenpox, which can be fatal. Congenital chickenpox syndrome manifests as low birth weight, scarred skin lesions, limb atrophy, optic nerve atrophy, internal visual obstruction, intellectual disability, and susceptibility to secondary bacterial infections.
3. Bullous chickenpox: Vesicles merge to form bullae. Necrosis of the skin and subcutaneous tissue at the rash sites may lead to gangrenous chickenpox.
The clinical symptoms of typical cases are usually classic, making diagnosis straightforward. When necessary, the following laboratory tests may be selected: ① Examination of fresh vesicular fluid under electron microscopy can reveal herpesvirus particles, allowing rapid differentiation from smallpox virus. ② Within the first 3 days of illness, inoculation of vesicular fluid onto human embryonic amniotic membrane tissue yields a high positive rate for virus isolation. ③ Serological tests, commonly the complement fixation test, can be performed. Complement-fixing antibodies appear in the serum of chickenpox patients 1–4 days after the rash onset, peak at 2–6 weeks, and gradually decline after 6–12 months. Indirect fluorescent antibody testing can also be used. ④ PCR detection of VZV DNA in nasopharyngeal secretions is a sensitive and rapid method for early diagnosis.
bubble_chart Treatment Measures
The main approach is symptomatic treatment. The patient should be isolated. Generally, no medication is required, and enhanced care is sufficient. During the fever period, bed rest is advised. For those with high fever, antipyretics may be administered, along with easily digestible food and adequate fluids. Trim the nails to prevent scratching and rupturing the blisters. Change clothes and bedding frequently to keep the skin clean. For those with significant cutaneous pruritus, antihistamines may be given. For ruptured blisters, apply 1% Chinese Gentian Violet; if secondary infection occurs, topical anti-inflammatory medications may be used.
The use of adrenal corticosteroids is generally contraindicated. For chickenpox patients already taking corticosteroids due to other conditions, the dose should be reduced to physiological levels (approximately 1/10 to 1/5 of the usual therapeutic dose) as soon as possible, if feasible, and discontinuation may be considered if necessary.
Trials of vidarabine (Ara-A) or acyclovir for severe chickenpox or herpes zoster appear to have some effect. There are also reports of treatment with interferon or transfer factor. A single injection of 0.3–1 ml of attenuated measles live vaccine may accelerate the drying of chickenpox blisters and prevent new eruptions.
For those with high fever and severe systemic symptoms, Chinese medicinals that clear heat, remove toxins, and cool the blood may also be used.
The prognosis of chickenpox is generally good. Most cases do not leave scars after the scabs fall off, but shallow scars may remain if the smallpox penetrates deep into the skin or secondary infections occur. These scars are usually oval-shaped and appear on the forehead and face. Severe cases or complications such as encephalitis or pneumonia can be fatal.
Patients should be isolated for respiratory precautions until all herpes lesions have dried and crusted over. In group settings, susceptible individuals exposed to the patient should be quarantined for 3 weeks (observation may begin from the 11th day after exposure). Air, bedding, and utensils contaminated by the patient's respiratory secretions or rash contents should be disinfected using methods such as ventilation, ultraviolet irradiation, sun exposure, or boiling. Foreign reports indicate that varicella-specific immunoglobulin (VZIG) can be used for prevention in immunocompromised individuals, pregnant women, and newborns whose mothers currently have chickenpox. Placental globulin or convalescent serum from chickenpox (collected within 1 month after the disappearance of chickenpox) should only be used for the weak or those with pre-existing chronic diseases; the effectiveness of placental globulin is uncertain.
Since general chickenpox symptoms are mild, it was previously considered less necessary to use VZV vaccines for prevention. Later, it was discovered that leukemia patients are prone to fatal complications from chickenpox, so the use of VZV vaccines specifically for leukemia patients has achieved satisfactory results. In recent years, due to complications from group A streptococcal infections causing severe and life-threatening conditions in children with chickenpox, the United States implemented a policy in 1995 requiring all infants, children, adolescents, and adults who have not had chickenpox to receive VZV vaccination as a preventive measure against chickenpox.
It is generally uncommon, but the more frequently seen complications include the following.
(1) Secondary bacterial infections: These include localized pustular secondary infections of the rash, cellulitis, acute lymphadenitis, erysipelas, sepsis, etc.
In recent years, reports from the United States indicate that children with chickenpox may develop invasive Group A streptococcus (GAS) infections, often occurring between the 3rd and 6th day after the onset of chickenpox. This can manifest as cellulitis with localized redness and swelling or streptococcal toxic shock-like syndrome (ISLS), both of which are severe conditions with a high mortality rate. Prompt preventive and treatment measures are crucial.
(2) Chickenpox encephalitis: Approximately 1 in 1,000 to 10,000 cases may develop encephalitis. It mostly occurs between the 3rd and 8th day of the illness, though a few cases may appear 2 weeks before the eruption or up to 3 weeks after. The severity varies, with symptoms and cerebrospinal fluid findings similar to those of general viral encephalitis. The mortality rate ranges from 5% to 25%. Other rare neurological complications include transverse myelitis, peripheral neuritis, and optic neuritis.
(3) Primary chickenpox pneumonia: This is more common in adult chickenpox patients and immunocompromised individuals. Mild cases may be asymptomatic or present only with a dry cough, while severe cases may involve hemoptysis, chest pain, shortness of breath, cyanosis, and fever. In critical cases, it can be fatal, particularly for those infected during the late stage [third stage] of pregnancy. Signs are often subtle. Pneumonia symptoms typically appear 2–6 days after the eruption but may also occur before the eruption or up to 10 days afterward. Diagnosis relies mainly on X-ray findings. Some reports suggest that 16% of adult chickenpox cases develop pneumonia based on X-ray evidence, though only 4% exhibit clinical symptoms.
(4) Others: Chickenpox and Reye syndrome often occur during the late stage [third stage] of chickenpox, accompanied by vomiting, restlessness, and irritability, progressing to cerebral edema. The brain pathology is associated with hyperammonemia. Since aspirin is also considered linked to Reye syndrome, it is recommended abroad to avoid aspirin for fever reduction during chickenpox infection. Myocarditis, nephritis, arthritis, and hepatitis are all rare complications.
Severe patients and those with concurrent bacterial infections need to be differentiated from the following diseases.
(1) Impetigo: Commonly occurs around the nose and lips or on exposed areas of the limbs. Initially appears as herpes, then develops into pustules, and finally forms scabs. It does not appear in batches and is not found on mucous membranes, with no systemic symptoms.
(2) Papular urticaria: Presents as spindle-shaped edematous red papules, about the size of peanuts, with a needle-tip or foxtail millet-sized papulovesicle or blister at the center. The lesions feel hard and are very itchy. They are distributed on the limbs or trunk, do not affect the head or mouth, and do not form scabs.
(3) Herpes zoster: The herpes follows a specific nerve pathway, is asymmetrical, and does not cross the midline of the trunk. There is significant localized burning pain.
(4) Smallpox: Severe chickenpox resembles mild smallpox. Key points for differentiation are listed in Table 11-12.
(5) Other viral infections: Herpes simplex virus infection can also cause chickenpox-like skin lesions. Such disseminated herpes simplex virus infections often occur secondary to atopic dermatitis or eczema. Confirmation relies on viral isolation results. In recent years, enteroviruses, especially Coxsackievirus A, have been found to cause widespread chickenpox-like rashes, typically occurring in late summer and early autumn when enteroviruses are prevalent. These rashes are often accompanied by lesions in the throat, palms, and soles, which helps differentiate them from chickenpox.
Table 11-12: Differentiation between chickenpox and smallpox
Chickenpox | Smallpox | ||
| Patient age | Mostly children | Both children and adults can be affected | |
| Vaccination history | Unrelated to vaccination | Never vaccinated, not vaccinated for many years, or vaccination failed | |
| Exposure history | Chickenpox patients in the same area with contact history | Smallpox patients in the same area with contact history | |
| Incubation period | Longer | Shorter | |
| Prodromal period | Shorter, no more than 24 hours | Longer, eruption begins after 3–4 days | |
| Systemic symptoms | Milder | More severe | |
| Rash | Distribution | Centripetal, mostly on the trunk | Centrifugal, mostly on the head, face, and limbs |
| Characteristics | Sparse rash, mostly oval, often with central depression, superficial lesions, no firmness, rarely forms pustules | Dense and larger rash, mostly round, with central depression, deeply embedded in the skin, feels firm like a small bean, has a pustular stage | |
| Development Law | Rashes at various stages are often seen in the same area | Most rashes on the same part of the body are of the same type | |
| Scar | Generally no scarring after healing | Scarring remains after healing | |
