Authors: Wendy J. van Zuijlen, PhD & Stuart T. Hamilton, PhD
You have a fever, sore throat, swollen glands, and are exhausted. Here we go again - you have the flu caused by that nasty influenza virus. But wait. Is it the flu? Did you know these symptoms can also be triggered by a herpes virus called cytomegalovirus (also known as CMV for short)?
When was Cytomegalovirus discovered?
CMV was identified back in the 1950s by Nobel Prize laureates, whose discovery paved the way for our polio, chickenpox, and measles vaccines. Yet, most people have not heard of CMV. Interested in learning more about this under-recognized virus? Of course you are. Sit back, relax, and read on.
What is a CMV infection?
Once CMV has infected a cell to replicate itself, the cell swells up with clumps of CMV DNA and protein, called inclusion bodies. The large appearance inspired its name cytomegalovirus, which comes from the Greek roots cyto and megalo, meaning “big cell”. Together, it is pronounced as “sy-toe-MEG-a-lo-virus”.
CMV can infect a remarkably broad range of cells within our body. For example, cells of our skin and blood vessels, connective tissue, muscles, blood, and even the placenta during pregnancy. Interestingly enough, these CMV-infected cells look like an owl’s eye and can easily be spotted under a microscope.
How is CMV transmitted?
CMV spreads via our bodily fluids – such as saliva, urine, blood, semen, and breast milk from an infected person. This means that someone can become infected with CMV:
- Through sexual contact with a CMV-infected person
- From direct contact with young children (who are famous for shedding CMV in their saliva and urine)
- Through a CMV-infected organ or bone marrow transplant, or blood transfusion
- From the mother during pregnancy, when CMV passes from an expectant mother’s blood through the placenta and infects the developing baby
Similar to what you may know from SARS-CoV-2, you can become re-infected with a different variety of CMV. This re-infection is called a non-primary CMV infection.
How common is a CMV infection?
CMV is a common virus that infects most of us at some stage of our lives.
- One in three children are already infected with CMV by the age of five
- More than half of adults are infected by the age of 40
- About 1 in 200 babies are born with CMV infection each year
Can Cytomegalovirus be cured?
After infection, CMV is not cleared from our body, though. It silently stays dormant or “asleep” at low or undetectable levels in our white blood cells and bone marrow for the rest of our lives. This is called latent CMV infection.
Latent CMV can start replicating again when our immune system weakens – such as after treatment with corticosteroids, chemotherapy, and immunosuppressive therapy. Interestingly, the hormonal changes during pregnancy may also stimulate latent CMV to “wake up” and start replicating again.
How dangerous is an infection with CMV?
While CMV can infect anyone, our healthy immune system usually stops CMV from causing any symptoms. Some people may get flu-like symptoms or mononucleosis (kissing disease). They usually feel better without treatment within three weeks.
On the other hand, CMV infection can have serious consequences in pregnancy and for people with a weakened immune system – such as people who had an organ or bone marrow transplantation and people living with human immunodeficiency virus (HIV).
Cytomegalovirus and pregnancy
Even though a pregnant woman herself may not feel sick, CMV in her blood may cross the placenta to infect her unborn baby. This is called congenital CMV, and may increase the risk of a miscarriage, stillbirth or lifelong illness for the baby. In fact, did you know CMV is the leading non-genetic cause of fetal malformation in developed countries and more common than Down Syndrome and Sudden Infant Death Syndrome?
Most babies born with congenital CMV never show any symptoms. Although, some babies have health problems at birth or develop them later in life, even as long as up to five years of age. One out of 5 babies who were infected with CMV during pregnancy have one or more symptoms, such as:
- Rash
- Yellowing of the skin or whites of the eye
- Low birth weight
- Enlarged liver and spleen
- Hearing loss (in one or both ears)
- Vision loss
- Seizures
- Mental disability
For more information or support, refer to the website of the National CMV Foundation in the US, the UK’s CMV Action, or the Congenital CMV Association Australia.
CMV infection with a weakened immune system
If someone is taking immunosuppressive therapy (e.g., (chemotherapy for cancer, prednisone/steroids, or drugs for autoimmunity) or lives with HIV, their immune system’s defenses are low (immunocompromised). In that case, CMV can replicate itself and may cause complications, including:
- Blurry vision or vision loss (CMV retinitis)
- Digestive system problems
- Lung infection
- Seizures, headaches, confusion (CMV encephalitis)
Therefore, immunocompromised people receive antiviral medication to decrease their risk or treat CMV disease. These antivirals stop CMV from replicating itself. They do not cure CMV infection, though. Sometimes, the virus is even “smart” enough to evolve to become resistant to these medications. Consequently, the medication stops working and the virus can replicate faster again.
How can you avoid catching CMV?
You can reduce your risk of CMV infection by avoiding contact with bodily fluids from a CMV-infected person. Therefore, the following precautions can help prevent catching CMV.
- Using a latex condom during sexual intercourse
-
Washing hands with soap and water for 15-20 seconds, especially after:
- changing nappies
- feeding a young child
- wiping a young child's nose or saliva
- Not sharing food, drinks, a toothbrush, or utensils used by young children
- Not putting a child's dummy (soother) in your mouth
- Avoiding contact with saliva when kissing a child (kiss on the forehead, not on the lips)
- Cleaning toys, countertops, and other surfaces that come into contact with children’s urine or saliva
Cytomegalovirus vaccine
At this moment, there is no approved CMV vaccine. However, several exciting clinical studies are investigating the safety and effectiveness of some candidate CMV vaccines. If one or two of these CMV vaccines are approved by the regulatory agencies (fingers crossed), then this could positively change the natural history of CMV infection as we know it. In the meantime, you too can help by raising awareness about this under-recognized virus and practicing good hygiene techniques around those who are most vulnerable.
ImmunoWars Gameplay Guide for CMV
In the endless battle between Mr. White and Mr. Black, CMV is a virus that is used by Mr. Black supporters to infect their opponents. Join Mr. Black and infect Mr. White defenders, as CMV is quite effective against the immune system card, the monocyte.
After three turns CMV will take two health points, and one additional health point every turn if your opponent has a monocyte equipped. Even worse, this infection cannot be treated with immunocards. How do you get rid of this pesky infection then you ask? You can always use CRISPR-CAS13 or use Bleach if you want to make a statement. Or who knows, maybe you will get lucky and get cured from all infections with the Herd immunity card or from one infection with the Spontaneous remission card.
Of course, prevention is better than cure, as CMV is sexually transmitted, you can use preventative measures such as wearing a condom to avoid getting infected at all. Wearing the Chastity belt will also provide some protection, it will protect you from any sexual activities in the game.
References:
- https://www.cdc.gov/cmv/overview.html (Symptoms of CMV)
- Ho M. Med Microbiol Immunol. 2008;197:65-73. (Isolating/identifying and naming CMV)
- Boppana SB, et al. Vaccine. 2023;41:S53-S75. (Epidemiology, transmission, vaccines in trials)
- Rawlinson WD, et al. Lancet Infect Dis. 2017;17:e177-e188. (Prevention of CMV infection)
- van Zuylen WJ, et al. Obstet Med. 2014;7:140-146. (Clinical presentation)