Chickenpox and Shingles

Chickenpox does not infect chickens nor is it caused by a pox-virus. A herpesvirus is its cause.

ž  One Virus, Two Diseases.

Infectious Agent

Varicella Zoster Virus (VZV) is a herpesvirus which causes both chickenpox (varicella) and shingles (zoster).

It is a medium-sized (100-200 nm diameter) double stranded DNA of the herpesvirus group, in the genus Varicellovirus.

It has no animal reservoir (Meaning that humans are the only natural hosts for VZV).

It is morphologically identical to the herpex simplex virus

Chickenpox Defined

Chickenpox is an acute and highly contagious disease of viral etiology that is characterized by vesicular eruptions on the skin and mucous membrane with mild constitutional symptoms.

*Etiology - origin

*Constitutional symptoms refer to a group of symptoms that can affect many different systems of the body.

Chickenpox commonly appears in children and it is usually clinically apparent. Other herpes group virus are usually asymptomatic.

*asymptomatic  means there are no symptoms. There are no symptoms and no detectable lesions at the site of entry into the body.

Shingles Defined

Shingles is the clinical manifestation due to the reactivation of VZV. VZV remains latent in the dorsal root of cranial nerve ganglia after primary infection (chickenpox). The stimulus to reactivation is unknown, but the virus travels from sensory ganglia to the skin, where multiplication resumes and produces crops of tender, persistent vesicles.

Reactivation may be triggered by imbalances between host and virus that are induced by diverse phenomena such as sunlight, X-ray treatments, emotional and physiologic stress, intercurrent infection, or immunosuppression associated with age, certain disease, or drug therapies (e.g. corticosteroids and cytotoxics). 

It can occur at any age in a person who has had a primary infection (chickenpox) but becomes increasingly common with advancing age.

Origin of Chickenpox’s Name

In a medical history book, it claims that Giovanni Filippo of Italy was the original physician to describe this disease, between the dates of 1510 and 1580.

In 1600, Richard Morton who was an English physician believed that chickenpox was a mild form of the smallpox. Thus a “chicken” version of small pox.

But in the 1700’s, another English physician William Heberden proved that the chickenpox is different from small pox.

Another theory is that the rash of chickenpox looks like the peck marks caused by a chicken.

When chickenpox was first described, it was noted that the pox lesions looked more like they were placed upon the skin rather than being a part of the skin themselves. In fact, people long ago felt they looked like chick peas placed upon the skin. The Latin word for chick peas is cicer which is the original word that chicken pox got its name.

The term chicken pox is derived from an Old English term called “giccin”, meaning itching.

Origin of Shingles’ name

Shingles comes from the Greek term zoster, meaning "belt" or "girdle", probably named after the characteristic belt-like dermatomal rash.

Shingles is derived from the Latin term cingulatus meaning to encircle or wrap around.

Synonyms

Pox     

Chickenpox

Varicella (chickenpox is the common name for varicella)

Varicella Zoster Viruz (VZV)

Human herpes virus type 3

“Bulutong-tubig”

Mode of Transmission

Infection can be spread by respiratory secretions and direct contact with moist lesions.

Indirect transmission - Contact with article of clothing or other item infected with fresh drainage from open blisters.

Children experiencing a mild case, with only few lesions and no other symptoms, often spread the disease.

Susceptible children, can easily contract chickenpox from exposure to adults with shingles.

People can acquire chickenpox by being exposed to the fluid of shingles lesions.

Signs and Symptoms of Chickenpox

Most cases of chickenpox are mild, sometimes unnoticed, and recovery is usually uncomplicated.

After an incubation period of about 2 weeks (With a range of 10 to 21 days), the earliest symptoms to appear are malaise and fever, soon followed by the rash. The skin lesions of varicella infection become apparent approximately 14 to 16 days after initial exposure. The lesions appear at different times, and within a day or so they go through a characteristic evolution.

The lesions begin as small, irregular, rose-colored spots called macules to little bumps called papules then to small blisters called vesicles then to pus-filled blisters called pustules, surrounded by a narrow zone of redness. After the pustules break, leaking virus-laden fluid, a crust (scab) form, and then healing takes place.

The lesions appear in cyclic crops over 2 to 4 days as the virus go through the cycles of replication. Usually the lesions are all fully crusted over by 10 days, usually healing completely but sometimes leaves a tiny pit or scar.

The illness usually lasts 4 to 7 days; new lesions stop appearing after about 5 days.

Cases are infective from 1 to 2 days before the rash appears until all the lesions have crusted (usually 4 days after the onset).

Lesions number from a few to hundreds and are more abundant in adolescents and adults that in children.

The lesions are pruritic and scratching may lead to serious, even fatal, secondary infections by Streptococcus pyogenes or Staphylococcus aureus.

The distribution of the rash is centripetal, first on the trunk and then on the face and the scalp, the limbs, and the buccal, and pharyngeal mucosa in the mouth. Lesions in the mouth may be painful.

*pruritic – itchy

In general, chickenpox in adults who have not had it as children is more severe than in children.

In about 20% of adults, varicella pneumonia develops, causing rapid breathing, shortness of breath, and a dusky skin color. The pneumonia subsides with the rash, but respiratory symptoms often persist for weeks.

Varicella pneumonia is rare in healthy children but it is the most common complication in neonates and immunocompromised patients. For the adults, it is the smokers who generally acquire pneumonia.

Immunocompromised patients are at increased risk of complications of varicella including those with malignancies, organ transplants or HIV infections and those receiving high doses of corticosteroids. The virus can damage the lungs, heart, kidney, and brain, resulting in death in about 20% of the class.

The varicella virus can cross the placenta following maternal viraemia and infect the fetus. Two types of intrauterine infection are noted:

1. The fetal varicella syndrome – Baby has a characteristic scarring of the skin, hypoplasia of the limbs, and chorioetinitis

2. Neonatal (Congenital) varicella – The babies are born with such defects as underdeveloped head and limbs, and cataracts

Signs and Symptoms of Shingles

It begins with pain in the area supplied by a nerve of sensation, often on the chest or abdomen but sometimes on the face or an arm or leg.

After a few days to 2 weeks, a rash characteristic of chickenpox appears, but unlike chickenpox, the rash is usually restricted to an area supplied by the branches of the involved sensory nerve.

The trunk, head, and neck are most commonly affected. Shingles have the characteristic assymetrical distribution on the skin of the trunk or head.

In people with AIDS or other serious immunodeficiency, instead of being confined to one area, the rash often spreads to involve the entire body, as in a severe case of chickenpox.

The disease generally heals in a benign fashion, with facial involvement, it may spread contiguously along the ophthalmic branch of the trigeminal nerve to the eye, resulting in severe pain and threatening sight.

 The lesions may be associated with prolonged disabling pain that can remain for months, long after the vesicular lesions disappear.

The most common complication of zoster in the elderly is post herpetic neuralgia – intractable pain persisting for 1 month or more after the skin rash.

Prevention of Chickenpox

Rare instances will a person acquire chickenpox more than once. In most cases, having chickenpox as a child confers lifelong immunity. Recurrences (in the form of shingles) are seen only in individuals with low concentration of Varicella-zoster virus antibodies and cell-mediated immunity.

A live attenuated vaccine was approved in 1995 for general use in the United States. A similar vaccine has been used in Japan for about 30 years. It is recommended as a single dose between the ages 12 to 18 months.

The vaccine is recommended for all healthy persons age 12 months or older or who do not have a history of chickenpox or who lack laboratory evidence of immunity to the disease. It is not given during pregnancy, and pregnancy should be avoided for 3 months after vaccination because of fear the vaccine might result in congenital varicella syndrome. The vaccine is highly effective at inducing protection from varicella in children (80-85% effective), but less so in adults (70%). About 5%of individuals develop a mild vaccine-associated rash 1 month after immunization. The vaccine is about 95% effective in preventing severe disease. Transmission of the vaccine virus is rare but can occur when the vaccinee has a rash. The duration of protective immunity induced by the vaccine is unknown, but is probably long term. Varicella infections can occur in vaccinated persons, but they are usually mild illnesses.

ž  Viravax (Varicella virus vaccine live)

Prevention of Shingles

In 2006, the FDA approved a unique vaccine called Zostavax. It is intended for adults ages 60 and over. It  reduces the incidence of shingles by 50%, and greatly reduces the seriousness and pain level of those who still develop shingles.

Treatment of Chickenpox

Several antiviral compounds provide effective therapy for varicella, including acyclovir, valacyclovir, famciclovir, and foscarnet. Acyclovir can prevent the development of systemic disease in varicella-infected immunocompromised patients. Valacyclovir and famciclovir requires less frequent dosing. Trials have shown that high dose oral acyclovir shortens the course of varicella in healthy children and adults by 1 day if commenced within 24 hours of the onset of the rash.

Treatment of Shingles

There are antiviral agents like Acyclovir, Valaciclovir (Valtrex). Nerve pain is sometimes helped by neurontin, or by a lidocaine patch. 

Epidemiology

Varicella is highly infectious, being spread mainly by the respiratory route.

Most cases of Varicella occur in children under 10 years of age, usually between the ages of 5 & 9.

Chicken pox is endemic in industrialized societies in the temperate zone, and its incidence is highest in March and April.

It is much more common in winter and spring than in summer in temperate climates.

Mortality rate from varicella is surprisingly high in otherwise healthy adults, particularly smokers, who develop pneumonia.