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5 Latent Viruses That Can Become Reactivated

cartoon shield with health sign blocking viruses

Viruses are microorganisms that are usually much smaller than bacteria and outnumber bacteria by 10 times. Viral infections are some of the most dangerous infectious diseases to afflict the human race. They include AIDS, COVID-19, smallpox, measles, Ebola, and the H1N1 swine flu. Antibiotics cannot kill viruses. However, antiviral medications and vaccines can prevent viral infections and/or reduce the severity of viral diseases. 

Most viral infections clear in a few days to weeks. However, some viruses can remain in the body after the initial infection, and the infected individual can undergo virus reactivation later. 

Please continue reading to learn about some dormant viruses that can undergo viral reactivation and cause recurrent symptoms or health complications in the host. 

How do viruses replicate?

A virus cannot replicate alone, i.e., it cannot multiply, reproduce, or thrive outside a host body. Viruses infect human cells and use components of the host cell to make copies of themselves. The viral life cycle often results in the death of the host cell and causes disease symptoms in the infected person. These viral infections are called lytic infections because they cause “lysis” or disintegration of infected cells.

What is a latent virus?

Most viruses are wiped out when the body’s immune system launches an attack against them. However, some viruses are latent viruses. They can remain in the body and enter what is called a “latent phase.” This is a phase in which the virus is quiescent, i.e., it is inactive or dormant and does not actively replicate or multiply. The virus does not kill or even damage the host cells during the latent viral phase or silent phase. However, the viral genome (genetic material) and infectious virus particles remain in the body.

At a later date, sometimes even years after the primary infection, the latent reservoir of virus that remains in the body can undergo a process of reactivation and re-enter an active phase of replication. The reactivation can be provoked by external or internal factors or a combination of both. In the following paragraphs, we’ll describe some latent viruses that can cause such a latent viral infection. 

Persistent Infections vs. Latent Infections

There is also something called a persistent infection which is different from latent infections. Like latent viruses, persistent viruses are not eliminated from the host’s body following the primary infection. The viral gene remains in some cells and continues to replicate slowly and silently. The infected individual thus experiences a persistent infection, but because the replication is at a low level, there isn’t any excessive damage to the host cells. An example of a persistent virus is the hepatitis B virus which causes viral hepatitis.

Causes of Viral Reactivation

A latent virus can become reactivated due to several stress factors, such as infections, including viral infections by other viruses, trauma, fever, or treatment with immunosuppressive or anticancer therapy. Essentially, a latent virus can sense that the host’s immune system is compromised and become reactivated. Often, the reactivation of a latent infection occurs without any internal or external triggers. 

Which viruses can become reactivated?

Some viruses are that are known to undergo viral latency and reactivation are described below.

Herpes Simplex Virus

First on our list of latent viruses is the herpes virus family. Herpes simplex virus type 1 (HSV-1) causes oral herpes (fever blisters or cold sores in and around the mouth). Herpes simplex virus type 2 (HSV-2) and HSV-1 both cause genital herpes. Infections with human herpesvirus are extremely common. The herpes viruses can establish a latent infection in the nerve cells of the host. A variety of triggers can lead to HSV reactivation of the latent virus, such as surgery, psychological stress, fever, menstruation, and exposure to sunlight.

Varicella Zoster Virus (VZV)

Virus infection with the varicella-zoster virus causes varicella (chickenpox). The virus can remain latent in nerve cells for years. Reactivation of the varicella-zoster virus can result in herpes zoster (shingles), which is a painful rash. Advancing age, immunosuppression (reduced immune response), emotional stress, acute or chronic diseases such as cancer or infections, and a re-exposure to the virus can lead to a reactivation of the latent VZV virus.

Epstein-Barr Virus (EBV)

The Epstein-Barr virus causes infectious mononucleosis or “mono,” a prevalent viral disease in humans. Latent viral reactivation can occur in previously infected people triggered by psychological stress or a weakened immune system. Viral reactivation of EBV infections is also seen in people with cancers, autoimmune diseases, chronic fatigue syndrome, and those admitted to an intensive care unit.

Cytomegalovirus (CMV)

This is a common viral infection that typically does not cause any symptoms in healthy people. However, a CMV infection can be fatal in immunosuppressed patients, such as those who have undergone an organ transplant or bone marrow transplant. The most common cause of CMV reactivation is a weakened immune system. People with diseases like HIV that compromise the immune system are also prone to CMV virus reactivation. 

Human Immunodeficiency Virus (HIV)

The human immunodeficiency virus (HIV) is a virus that attacks the body’s immune system. A latent HIV infection can last long before the virus becomes active and starts causing symptoms. Indeed, the virus latency can last 10-15 years, during which time HIV stays dormant. Stressful conditions, such as inflammatory conditions, tumors, or co-infection by other viruses, can reactivate the latent virus.

What about SARS-CoV-2? Can it undergo virus reactivation?

Research on SARS-CoV-2, the virus that causes the COVID-19 disease, is still ongoing. Infectious Disease specialists are studying its behavior to figure out if this virus can remain latent in the human body. Early research suggests that the virus may cause a latent viral infection, i.e., people who are believed to be cured of COVID-19 may test positive again due to reactivated virus rather than a re-infection. A person with a reactivated infection can potentially cause virus spread.

COVID “long haulers,” especially previously healthy people who are experiencing long-term symptoms after COVID, are of special interest to scientists. Researchers are trying to figure out whether the continuing symptoms are because their bodies are unable to put the virus into a dormant state. Only time will tell if SARS-CoV-2 is truly a virus that can undergo latent viral reactivation.

Wrapping Up

Viruses cause some of the most dangerous human infections. Some viruses cause severe disease and then disappear from the host’s body forever. However, other viruses can cause an initial lytic infection (active infection) during which time the virus actively replicates, followed by a period of latency when the virus enters a dormant or silent phase, causing no symptoms. Various triggers can cause latent viruses to re-enter the lytic phase by undergoing a process of reactivation. Different viruses that are known to be latent viruses, i.e., viruses that enter a latent phase after the initial infection, include the herpes simplex virus, varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, and HIV. 


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