Varicella zoster virus

A tiny germ causes chickenpox. This germ can make itchy spots on your skin. The spots may fill with fluid. They then turn into scabs. This germ can stay in your body for a long time. It hides in your nerves. Later, it can wake up. When it wakes up, it causes shingles. This happens to many adults. It can make the skin feel like it is burning. Vaccines can help keep you safe from this germ.

The varicella zoster virus is a tiny germ. It is one of nine herpes viruses that can infect people. This virus causes two main illnesses.

First, it causes chickenpox. This often affects children and young adults. The virus enters through the breathing system. It can stay in the body for 10 to 21 days before signs appear. People get itchy spots on their skin. These spots fill with fluid and then turn into scabs. Most spots appear on the face, chest, and back.

After a person gets better, the virus does not leave. It stays dormant, which means it sleeps, in the nerves. Many years later, the virus can wake up. This causes shingles. Shingles is a disease that mostly affects adults. It can cause a burning pain on one side of the body. About 1 in 4 people will get shingles in their life. For people over age 85, the risk is 1 in 2.

Doctors use vaccines to help prevent these illnesses. One vaccine helps children avoid chickenpox. Another vaccine called Shingrix helps adults avoid shingles. Shingrix is very strong. It can protect people for many years.

The varicella zoster virus, or VZV, is a tiny germ that lives only in humans. It belongs to a group of nine known herpes viruses. This virus is special because it can cause two different illnesses. Most often, it causes chickenpox in children and young adults. Later in life, the same virus can wake up to cause shingles in adults. Scientists call this ability to stay in the body virus latency. This means the virus goes to sleep in your nervous system after you get better. It hides in the nerve cells for many years without causing any trouble.

Learning how the virus works helps us understand why it causes two diseases. First, the virus enters through the breathing system. It has an incubation period, which is the time before you feel sick. This usually takes about 14 days. The virus then multiplies in the tonsils and targets the skin. You might see small spots that fill with fluid and then turn into scabs. These spots often appear on the face, chest, or back. After the chickenpox goes away, the virus stays dormant in the nerve clusters. If the virus reactivates, it travels along the nerves to cause shingles. This often feels like a burning pain on just one side of the body.

People have known about these skin rashes for a very long time. Ancient civilizations even wrote about chickenpox-like rashes. However, people did not realize that shingles and chickenpox were caused by the same virus until 1888. In 1943, scientists noticed that virus particles from both illnesses looked the same. Later, Evelyn Nicol and Thomas Huckle Weller worked to isolate the virus itself. This work helped us understand the germ much better. By 1974, the very first chickenpox vaccine was introduced to help protect people.

There are many important facts about how this virus moves through the world. VZV can survive in the air or on surfaces for a few hours. In Sweden, a 2015 study found about 315 shingles cases for every 100,000 people each year. For adults over age 85, the risk of getting shingles is 1 in 2. The virus also has different types called clades. Clades 1 and 3 are found in Europe and North America. Clade 2 is found in Asia, especially Japan. Clade 5 is found in India. These different groups help scientists track how the virus spreads.

We use science to stay safe from VZV through vaccines and medicine. There is a vaccine called Varivax that helps protect children from chickenpox. For older adults, a vaccine called Shingrix is very helpful. Shingrix was approved in 2017 and is very strong against shingles. It is given in two doses to make sure the protection lasts. Some studies even suggest that this vaccine might help lower the risk of dementia. Doctors can also use medicines like acyclovir to treat people when they are sick. These tools help keep our bodies healthy even when the virus is around.

The varicella zoster virus, or VZV, is a human-specific pathogen. It belongs to the herpesvirus family. Specifically, it is known as human herpesvirus 3 (HHV-3). This virus is unique because it causes two distinct clinical diseases. It causes chickenpox, or varicella, in children and young adults. Later in life, the same virus can reactivate to cause shingles, or herpes zoster. Understanding VZV is vital for public health. It helps scientists develop vaccines to prevent these two different stages of illness.

The infection process begins when the virus enters the respiratory system. After entry, there is an incubation period. This is the time before symptoms appear. The average incubation period is 14 days, but it can range from 10 to 21 days. The virus then multiplies in the tonsils. It eventually targets the skin and peripheral nerves. During the primary infection, the illness typically lasts about 3 to 4 days. Infected people are most contagious 1 to 2 days before their skin lesions appear.

VZV has a complex way of staying in the body. This is called virus latency. After a person recovers from chickenpox, the virus does not leave. Instead, it lies dormant in neurons. It hides in the cranial nerve ganglia, the dorsal root ganglia, and the autonomic ganglia. These are clusters of nerve cells. Many years later, the virus can reactivate. When it wakes up, it travels along the nerves to cause shingles. Shingles lesions often cause neuropathic pain. This pain is frequently described as a burning sensation. It usually occurs on only one side of the body.

Scientists have studied the structure of VZV for decades. The virus is a spherical particle. It is between 180 and 200 nm in diameter. It has a lipid envelope that covers a 100 nm nucleocapsid. This nucleocapsid is made of 162 capsomeres in an icosahedral form. The genome is a single, linear, double-stranded DNA molecule. It is 125,000 nucleotides long. The genome has at least 70 open reading frames. VZV is closely related to herpes simplex viruses (HSV). However, it lacks the HSV gD protein. It also does not produce latency-associated transcripts (LAT) like HSV does.

History shows how our understanding of VZV has grown. Ancient civilizations recognized chickenpox-like rashes. However, the link between shingles and chickenpox was not discovered until 1888. In 1943, researchers noted that the virus particles looked similar in both diseases. Later, Evelyn Nicol and Thomas Huckle Weller isolated the virus. This allowed for better medical responses. In the 1970s, Michiaki Takahashi and colleagues developed an attenuated Oka strain. This led to the development of the Varivax vaccine in the 1980s. The vaccine was approved by the FDA in 1995.

Epidemiological data show the significant impact of VZV. In a 2015 Swedish study, the annual incidence of shingles was 315 cases per 100,000 inhabitants. For people aged 50 or older, this rose to 577 cases per 100,000. The lifetime risk of developing shingles is between 20% and 30%. For people aged 85 and older, the risk increases to 1 in 2. Shingles can lead to serious complications. These include postherpetic neuralgia, which is chronic pain lasting over three months. It can also cause encephalitis or pneumonia. In rare cases, Ramsay Hunt syndrome type 2 can occur.

VZV also shows significant genetic diversity through various clades and genotypes. Clade 1 and 3 include strains from Europe and North America. Clade 2 consists of Asian strains, especially from Japan. Clade 5 is based in India. Clade 4 includes some European strains. Scientists use phylogenetic analysis to sort these into genotypes. There are nine known genotypes, such as E1 and E2. In a study of 342 specimens from 18 European countries, the E1 genotype was the most common at 65%. This diversity helps researchers track how the virus moves across the globe.