Chickenpox, medically known as varicella, is a contagious infection caused by the varicella-zoster virus (VZV).

Despite widespread vaccination efforts since the mid-1990s, it remains a significant health concern due to its high transmissibility and potential complications in vulnerable populations.

Transmission and Infectiousness

Chickenpox spreads primarily through inhalation of respiratory droplets released when an infected person coughs or sneezes. Direct contact with fluid from the characteristic chickenpox blisters can also transmit the virus. The contagious period begins one to two days before the appearance of the rash and continues until all blisters have crusted over.

Due to this high infectivity, chickenpox often rapidly propagates in group settings such as schools and childcare centers, with secondary attack rates ranging from 61% to 100% among susceptible individuals. The virus initially infects the mucosa of the upper respiratory tract before disseminating throughout the body via the bloodstream.

Clinical Manifestations

The hallmark symptom of chickenpox is a distinctive itchy rash that progresses through stages: red macules evolve into raised papules, then fluid-filled vesicles, followed by crusting and scabbing. This rash typically begins on the chest, back, and face, before spreading to other body parts. Accompanying symptoms frequently include fever, fatigue, sore throat, and headache, lasting about five to seven days. The full disease course from exposure to complete healing generally spans two to four weeks.

Diagnosis and Immunity

While clinical diagnosis based on the evolving rash and symptomatology is generally reliable, laboratory confirmation may be necessary, particularly for vaccinated individuals or those with suppressed immunity. Polymerase chain reaction (PCR) testing of blister fluid or scabs is considered the most accurate diagnostic method for detecting VZV DNA. Serological tests measuring specific antibodies can assess immunity status following exposure or vaccination.

Complications and Risk Factors

Though many chickenpox cases resolve without incident, serious complications can arise, particularly in immunocompromised patients, pregnant women, neonates, and old people. Pneumonia represents one of the most severe complications, posing significant morbidity. Bacterial superinfection of skin lesions and neuro-inflammatory conditions such as encephalitis or meningitis, though rare, are grave concerns.

Individuals receiving prolonged steroid therapy or those with cellular immune deficiencies face elevated risks for complicated varicella infections. Neonates born to mothers who develop chickenpox shortly before or after delivery are especially vulnerable to severe disease.

Preventive Measures: Vaccination and Post-Exposure Prophylaxis

Vaccination remains the most effective measure to prevent chickenpox infection and its associated complications. Since the introduction of the varicella vaccine in 1995, incidence rates and severe disease hospitalizations have markedly decreased. The vaccine prevents approximately 70% to 90% of varicella infections and up to 95% of severe cases. Routine childhood immunization is widely recommended.

Post-exposure vaccination, if administered within three days of contact, can mitigate illness severity in children. For immunocompromised patients or pregnant women with recent exposure, varicella-zoster immune globulin offers an alternative prophylactic option.

Beate Kampmann, Professor of Paediatric Infection and Immunity at the London School of Hygiene & Tropical Medicine (LSHTM), said:

“Whilst in most cases chickenpox is an annoying but usually fairly harmless infection in children, we must not overlook the really severe cases that can be caused not only by the chickenpox virus but also by superinfections, and we have certainly seen many - even fatal - cases in our paediatric intensive care units. I have personally looked after these kids for many years.”

Chickenpox continues to be a highly contagious illness with distinct clinical features and potential complications. Advances in vaccination have significantly lowered its prevalence and severity, yet understanding transmission dynamics, diagnostic methods, and risk factors remains essential for effective management. Continued public health efforts focused on vaccination coverage and timely interventions are vital to minimizing the impact of this once-common childhood disease and safeguarding at-risk individuals.