The Forever Viruses: How Herpes Viruses Lie Dormant and Reawaken

Herpes virus (DNA virus) courtesy of Wikimedia Commons

Viruses are non-living invaders who penetrate the body's defenses. Once in the body, viruses replicate, which can lead to illness. Some viruses within the herpes family (called herpesviridae) can remain dormant inside the cells until there is a trigger such as stress or immune system comprise. This article will discuss how herpes viruses elude the immune system and remain dormant in the human body and what happens if they reawaken.

How Viruses Invade and Make Homes in Human Cells

The herpes virus family are infectious microbes consisting of a segment of DNA surrounded by a protein coat (a capsid). Like other viruses, members of the herpes virus family cannot replicate alone. Instead, the virus invades a host cell and use components of the host cell to make copies of itself. Often, a virus ends up killing the host cell in the process, causing damage to the host organism. However, the herpes viruses generally do not pose a threat of serious illness in people with healthy immune systems.

Herpes viruses become latent by integrating their genetic material into the host cell's DNA or into a special plasmid called an episome. The virus then becomes inactive and dormant. Reactivation from latency occurs when internal cellular or environmental triggers the expression of viral genes, which leads to renewed viral activity and possibly symptoms.

Latency and Reinfection Among the Herpesviruses

The herpesviridae are more than just herpes simplex types 1 and 2. This viral family causes some of the most well-known infections. Virtually everyone has one or more of these viruses lying dormant within them. Among the most common viruses in this family include:

Herpes simplex type 1 and type 2 are latent viruses that cause fever blisters and cold sores on the mouth (type 1) or genitals (type 2). These viruses can cause periodic outbreaks after initial infection. Once an infection has healed, the virus hides in the nerve cells under the surface of the skin only to reactivate later on.

Varicella zoster virus causes chickenpox and then remains dormant in the host’s nerve cells for decades and then reactivate as shingles, which is a painful rash comprised of fluid filled blisters that resolves in 1 to 2 weeks. The Shingrix vaccine is available to reduce a person’s risk for reinfection or if infected, decrease the severity and risk of complications from shingles. The U.S. Centers for Disease Control and Prevention recommends people over the age of 50 receive two doses of Shingrix, with two to six months between doses.

Epstein-Barr virus (EBV) is known for causing the common illness of mononucleosis or

"mono," which is a common viral infection. Many people become infected with EBV during childhood, but they experience very mild symptoms or even none at all.

Once people are infected with EBV, they carry the virus in a dormant state for the rest of their lives. Stress and a compromised immune system can trigger reactivation, but usually it causes no symptoms. However, in rare cases, reactivation can lead to infection once again in people with weakened immune systems.

Cytomegalovirus (CMV) is a common herpesvirus that often causes asymptomatic or mild illness in healthy individuals but can lead to severe disease in those who are immunocompromised and newborns. After the initial infection, CMV establishes lifelong latency, primarily in immune cells such as macrophages and bone marrow progenitor cells, During latency, the virus remains dormant with limited gene expression and no production of infectious particles. This latent state allows CMV to evade immune detection. Reactivation occurs when the immune system is weakened such as from organ transplantation, HIV infection, or stress. Reactivated CMV can cause tissue damage and systemic illness, particularly in those with impaired immunity.

Conclusion

The thought that many common viruses, particularly the herpes family viruses, remain in the body for life is dismaying. However, knowing about these viruses is helpful if circumstances arise that lead to awakening such as immune system compromise. The viral power of latency enables them to remain undetected by the immune system for many years.

References

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Kerr J. R. (2019). Epstein-Barr virus (EBV) reactivation and therapeutic inhibitors. Journal of clinical pathology, 72(10), 651–658. https://doi.org/10.1136/jclinpath-2019-205822

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