Herpes simplex virus

Herpes simplex viruses are very common germs that affect many people. There are two main types known as HSV-1 and HSV-2.

These viruses belong to a large family called Herpesviridae. As of 2016, about 67% of people under age 50 had HSV-1. They are highly contagious and spread through close contact. Many people carry the virus but never feel sick at all. Some people might see small, watery blisters on their skin or lips. These sores eventually heal by forming a scab.

These viruses are experts at hiding inside the human body. They are called neurotropic viruses because they live in nerve cells. The virus stays safe from the immune system by hiding in the cell bodies of neurons. Sometimes, the virus wakes up in a process called reactivation.

During an outbreak, the virus travels through the nerve's long arm, called an axon. It moves from the nerve to the skin to make copies of itself. This is when new sores or blisters might appear on the body. This cycle of hiding and waking up can happen many times.

Scientists have studied these viruses for a long time to understand them. HSV has been a model virus for many studies in molecular biology. This means researchers use it to learn how cells and genes work. For example, scientists found one of the first functional promoters in eukaryotes using HSV. A promoter is a part of DNA that helps start the process of making proteins. They also studied a protein called VP16, which is a famous transcriptional activator. These discoveries help us understand how all living things use their genetic instructions.

A single virus particle is called a virion. It has a complex structure that helps it work. Inside, there is a double-stranded DNA genome. This DNA is kept inside a protein cage called a capsid. The capsid is shaped like a 20-sided object called an icosahedron.

A lipid envelope wraps around the capsid. A layer called the tegument connects the envelope to the capsid. The virus uses at least 74 different genes to build these parts. These genes control how the virus makes copies of itself.

Understanding how the virus spreads helps us stay healthy. The virus is very unstable outside of a human body. It loses its ability to infect others quickly once it hits the air. Because of this, you likely won't catch it from a towel or a toilet seat. Instead, it spreads through direct contact with skin or mucous membranes.

Most of the time, people spread the virus through asymptomatic shedding. This means the virus is present even if there are no visible sores. Even without blisters, the virus can still move from one person to another.