Epstein–Barr virus

A tiny germ lives in many people.

It can hide in your body for a long time. Most children do not feel sick from it.

Sometimes it makes you feel very tired. It can make your throat sore too. This is called mono.

This germ moves through spit. It can pass from person to person.

It can change how some cells work. This can make some people very ill.

Scientists are still looking for ways to stop it. Many people have had this germ before.

The Epstein–Barr virus is a very common germ. It is also called EBV.

Most people have had it. In the United States, about 90% of adults have had it.

This virus can move through saliva. This happens when people share spit. Many children do not feel sick at all. But when teens get it, they might get mono. Mono is a sickness that makes you very tired. It can also cause a sore throat and fever.

EBV is a special kind of virus. It can hide inside your cells. It stays in B cells, which are parts of your immune system. When it hides, we call this latency. This means the virus is quiet. It does not make new germs while it is quiet.

Sometimes, the virus wakes up. This is called lytic replication. It makes new copies of itself to spread. EBV can also change how cells work. It can make some cells divide forever. This can lead to cancer in some people. Scientists are still testing ways to make a vaccine. Right now, no vaccine is approved to stop it.

The Epstein-Barr virus, or EBV, is a very common germ. It belongs to the herpes family of viruses. Scientists also call it human herpesvirus 4. This virus is special because it can cause cancer. It is the first virus ever found that does this. EBV stays in the body for a long time. It makes a permanent home in B cells. These are important parts of your immune system.

EBV works by entering different types of cells. It can enter B cells and epithelial cells. To enter a B cell, a protein called gp350 grabs onto a receptor called CD21. Then, another protein called gp42 helps the virus fuse with the cell. For epithelial cells, the virus uses different proteins like BMRF-2. Once inside, the virus shell dissolves. The viral DNA then travels into the cell nucleus.

Inside the cell, the virus can do two different things. One way is called lytic replication. This is when the virus makes many new copies of itself. It uses its own DNA polymerase to copy its genome. The other way is called latency. During latency, the virus is quiet and does not make new germs. Instead, the viral DNA stays in the nucleus as a small circle. It uses the cell's own tools to copy itself.

Many people have had EBV in their lives. In the United States, about 90% of adults have it. About half of all five-year-old children also have it. When teens get it, they often get infectious mononucleosis. This is also called "mono" or glandular fever. It can cause a fever, sore throat, and extreme fatigue. Some people might even get diseases like Burkitt lymphoma.

EBV is linked to many different health issues. It can cause several types of cancer every year. About 200,000 cancer cases globally are linked to EBV. A large study in 2022 looked at 10 million US military members. It suggested EBV might be a leading cause of multiple sclerosis. This is a condition that affects the nervous system. Scientists are still working to find a good vaccine.

The Epstein–Barr virus, or EBV, is a member of the herpes family. Scientists also identify it as human herpesvirus 4 (HHV-4). It is a double-stranded DNA virus, meaning its genetic instructions are held in two strands. EBV is one of the most common viruses found in humans. It is also famous in science as the first identified oncogenic virus. An oncogenic virus is a germ that has the ability to cause cancer.

To understand how EBV works, we must look at its structure. The virus is between 122 and 180 nanometers in diameter. At its center is a double helix of DNA containing about 172,000 base pairs. This DNA encodes 85 different genes. The DNA is wrapped in a protein shell called a nucleocapsid. Surrounding that is a layer of protein known as the tegument. Finally, an outer envelope made of lipids and glycoproteins protects the virus. These surface proteins are essential for the virus to infect a host cell.

EBV uses different methods to enter different types of cells. This specific targeting is called viral tropism. To enter B cells, which are part of the immune system, the virus uses a protein called gp350. This protein binds to a cellular receptor called CD21. Another protein, gp42, then helps the viral envelope fuse with the cell membrane. To enter epithelial cells, the virus uses different tools. The protein BMRF-2 interacts with cellular β1 integrins. Then, the protein gH/gL interacts with αvβ6/αvβ8 integrins to trigger fusion.

Once inside a cell, the virus follows one of two main paths. The first is the lytic cycle, which is a productive infection. In this cycle, the virus makes many new copies of itself. The viral genome must become linear to do this. The virus uses its own enzyme, called DNA polymerase, to copy its DNA. This process happens in three stages: immediate-early, early, and late. Immediate-early genes act as activators for the later stages. Early genes help with replication and metabolism. Late genes produce structural proteins, such as the VCA that forms the viral capsid.

The second path is called latency. During latency, the virus does not produce new infectious particles. Instead, the viral DNA becomes a small circle called an episome. This circle sits in the cell nucleus. Unlike the lytic cycle, the virus uses the host cell's own DNA polymerase to copy itself. The virus stays quiet by using epigenetic changes, like DNA methylation, to suppress most of its genes. In B cells, the virus can follow three different latency programs: Latency I, II, or III. These programs determine which specific viral proteins and RNAs are produced.

EBV infection can change how B cells behave. It can lead to the "immortalization" of these cells. This means the virus causes the B cells to divide indefinitely. Normally, cells have a limited lifespan and eventually die. However, EBV proteins like EBNA-2, EBNA-3C, and LMP-1 allow these cells to keep growing. This ability to persist is why the virus can stay in a person for their entire life. Most people become infected and then gain adaptive immunity. In the United States, about 90% of adults show evidence of a previous infection.

While many people have no symptoms, EBV is linked to many serious conditions. It is the cause of 90% of infectious mononucleosis cases. This illness causes fever, sore throat, and extreme fatigue. EBV is also linked to several cancers, such as Burkitt lymphoma and Hodgkin's lymphoma. It can also cause gastric cancer and nasopharyngeal carcinoma. Globally, about 200,000 cancer cases each year are thought to be caused by EBV.

Recent research has also connected EBV to other major health issues. A 2022 study of 10 million US military members suggested EBV is a leading cause of multiple sclerosis (MS). The study suggested a recent infection could increase the risk of developing MS. The virus is also associated with autoimmune diseases like lupus and rheumatoid arthritis. It can even cause childhood disorders like Alice in Wonderland syndrome. Scientists are still testing various vaccine formulations, but none have been approved yet.