Chickenpox - Causes

Chickenpox (Varicella) is a highly contagious disease caused by the varicella-zoster virus, primarily transmitted through airborne droplets or contact with skin lesion secretions. This virus has a very high infectivity; approximately 90% of unvaccinated individuals will become infected after exposure to an infected person. The pathogenesis involves the virus invading the human body, replicating in the upper respiratory tract, then entering the bloodstream to cause systemic infection.

After initial infection, the virus remains latent in nerve ganglia and may reactivate later as herpes zoster when immunity declines. The causes of chickenpox can be divided into biological factors, environmental exposure, and personal behaviors. This article will provide a comprehensive analysis from the perspectives of genetic predisposition, living environment, behavioral patterns, and high-risk groups.

Genetic and Family Factors

Although chickenpox is mainly caused by viral transmission, genetic background may influence infection risk and severity of symptoms. Studies show that individuals with specific HLA genotypes have different immune responses to the varicella-zoster virus. Patients with particular human leukocyte antigens (HLA-A2, HLA-B13) may exhibit milder rash presentations.

Family history plays an indirect role in transmission pathways:

• The immune status of cohabiting family members directly affects the efficiency of virus transmission
• If someone in the family is vaccinated, it can form a herd immunity barrier
• Patients with inherited immune deficiencies (such as severe combined immunodeficiency) are more likely to develop severe illness after infection

Genetic polymorphism studies indicate that abnormal expression of Toll-like receptor 3 (TLR3) may reduce virus recognition ability, leading to prolonged fever cycles post-infection. However, genetic factors are not the primary determinants; environmental exposure remains the main pathogenic route.

Environmental Factors

Crowded environments are highly conducive to the spread of chickenpox. Closed spaces such as schools, daycare centers, and households, due to frequent interpersonal contact, can result in a basic reproduction number (R0) of 1.8 to 4.5. Virus-laden droplets suspended in the air can survive in the environment for several hours, creating covert transmission pathways.

Seasonal variations significantly impact incidence rates:

• In temperate regions, incidence during winter to spring is 30-50% higher than in summer
• Cold and dry climates may reduce mucosal moisture, increasing the likelihood of virus adhesion
• Poor indoor ventilation leads to accumulation of the virus in the air

Immunocompromised patients in healthcare settings are often infected via nosocomial transmission, accounting for about 15% of adult cases. Enclosed spaces in public transportation are also important transmission venues; a single patient can infect over 50% of fellow passengers.

Lifestyle and Behavioral Factors

Daily protective behaviors directly influence infection risk. Improper handwashing and sharing personal items (such as towels and clothing) increase opportunities for contact with the virus. Close contact activities like hugging and kissing are 3-4 times more efficient in transmission than non-contact methods.

The following behavioral patterns are associated with increased infection risk:

• Not vaccinated or incomplete vaccination
• Failure to isolate and observe after contact with an infected person
• Not wearing masks in public places
• Not using protective clothing when caring for patients

Parenting behaviors significantly impact young children: pregnant women infected with chickenpox in late pregnancy may lead to severe neonatal chickenpox. Postpartum contact with the virus may transmit immunity through breast milk, but this is not common.

Other Risk Factors

The immune system's status is a key regulatory factor. Organ transplant recipients on immunosuppressants have a 20-fold higher risk of infection and may develop rare complications such as visceral involvement. HIV-infected individuals with CD4+ T cell counts below 200/μL have a 35% rate of severe illness after infection.

Analysis of susceptibility in special populations:

• Infants under 12 months have lower incidence due to maternal antibody protection
• Adolescents and adults tend to have longer duration of fever after infection compared to children
• Patients with chronic skin conditions (such as pemphigus) on corticosteroid therapy are prone to extensive rash

Medical procedures can also increase exposure risk, such as performing dialysis during chickenpox outbreaks, where shared treatment equipment may lead to nosocomial infections. Use of biologic agents (like anti-TNF-α drugs) in rheumatoid arthritis patients increases the risk of bacterial skin infections by 40% after infection.

In summary, the occurrence of chickenpox results from the interaction of viral characteristics, host immunity, and environmental transmission pathways. Although genetic background influences individual responses, environmental exposure opportunities remain the main driving force. Improving vaccination rates, strengthening public health measures, and developing special protection strategies for immunodeficient patients are key to controlling the spread of the disease.

 

Frequently Asked Questions

How can I determine if the skin symptoms of chickenpox have entered the recovery stage?

The itching of chickenpox skin lesions usually goes through three stages: redness, blisters, and scabbing. When most blisters have dried and fallen off, and no new rashes appear for over 48 hours, it indicates the recovery phase. However, continuous monitoring for signs of secondary infection, such as redness, swelling, or pus at scab sites, is necessary, and medical attention should be sought if these occur.

Are adults more severely affected by chickenpox than children?

Yes, adults tend to experience more severe symptoms, including prolonged high fever, more intense skin inflammation, and potential complications such as pneumonia or encephalitis. This is because adults' immune responses to the virus are more vigorous. Vaccination is recommended for unimmune individuals to reduce risks.

Will chickenpox leave scars after recovery? How can I prevent this?

Scratching blisters can lead to scars, especially on the face or joints where they are more visible. It is advisable to trim nails, wear loose clothing to reduce friction, and use anti-itch ointments to relieve itching. Avoid squeezing blisters and keep the skin clean and dry to minimize scarring risk.

If vaccinated against chickenpox, can I still get infected? Does this mean the vaccine failed?

Breakthrough infections can occur after vaccination, but symptoms are usually milder and the disease course shorter. The vaccine is not 100% effective but significantly reduces the severity of illness. Breakthrough infections are a normal phenomenon caused by vaccine characteristics and do not indicate immune failure.

What are the effects of chickenpox infection during pregnancy on the fetus?

Infection during early pregnancy may lead to fetal complications such as scarring or organ abnormalities. Pregnant women who have been exposed should promptly receive immunoglobulin injections and consult a physician to assess risks. If the baby is not infected after delivery, maternal vaccination is recommended to protect the infant.