Varicella Zoster virus - An introduction
Varicella Zoster virus is a dermotropic and neurotropic virus which produces primary infection usually in childhood and may be reactivated later in life as the virus stays in the nerve cells of the body.
Disease caused by Varicella zoster virus
Varicella (chicken pox) - is the acute primary infection.
Zoster (Shingles or herpes zoster) – the recurrent form of infection that occurs due to reactivation of the latent virus.
Important properties of Varicella zoster virus
- Has all the characteristics of herpes virus
- Human are the natural host.
- It has worldwide transmission
- Has a single serotype
How is Varicella zoster virus transmitted?
Varicella Zoster virus is transmitted by respiratory droplets and by direct contact with the lesion.
Chicken pox may be contracted from a case of shingles but not vice versa.
Some important points:
Chicken pox in case of children is usually well tolerated. But it is extremely dangerous in adults, pregnant women and the immunocompromised. Also note that chicken pox may be contracted from a case of shingles but not vice versa.
Pathogenesis and immunity
The Varicella zoster virus infects the mucosa of the upper respiratory tract then spreads via the blood to the skin where typical vesicular rash occurs. After recovery from the primary infection the virus becomes latent usually in the dorsal root ganglia. Later in life, due to decreased immunity (cell mediated) or local trauma the virus becomes reactivated and cause zoster.
Immunity following Varicella is lifelong. More than 90% of people in the United States have antibody by the age of 10 years. But zoster can happen despite this immunity to Varicella. Zoster usually occurs only once. The frequency of zoster usually increases with advancing age usually due to decreased immunity.