Varicella and herpes zoster are manifestations of the same virus i.e. varicella virus. When a person comes in contact with the Varicella-Zoster Virus for the first time, he develops chickenpox. Even when he recovers, the virus remains latent in the nerves for years. In 15-20% of them, the virus is able to spread albeit locally along the nerve root causing herpes zoster. This occurs due to natural fading of immunity and hence occurs after the age of 40-50 years.
Shingles affects one in five adults, who were infected with chickenpox as children, especially those who are immune-suppressed, particularly from cancer, HIV, stress or other conditions.
Firstly, it can lead to pain, which can go on for months to years.
Lastly, herpes zoster if it occurs in immuno-compromised patients like HIV, it can lead to complications like pneumonia and brain damage.
Can herpes zoster be prevented?
Yes, by taking varicella vaccine before chickenpox, one can prevent contact with the wild virus and hence prevent both chickenpox and herpes zoster. The vaccine does not provide 100% immunity though.