What Is Cytomegalovirus?
What is cytomegalovirus?
Cytomegalovirus (CMV) is a member of the herpes virus family. Others viruses that belong to the same family are:
- Varicella-Zoster Virus - causes shingles and chickenpox
- Herpes Simplex Virus - causes genital herpes and cold sores
- Epstein-Barr Virus - causes “mono”, which is also known as infectious mononucleosis
Cytomegalovirus (CMV) is a common virus that can infect people of different ages. In the US, approximately 1 in 3 children are infected with CMV by the time they reach the age of 5, and more than half of adults have the virus by age 40. Once the virus enters the human body, it permanently stays in the body until it is reactivated. Other strains of CMV virus can also reinfect individuals who are already infected with the virus.
A healthy individual's immune system helps protect the body against the virus, which is why most people who are infected with CMV are asymptomatic. However, people who are immunocompromised can have serious health problems when they are infected with CMV. Unborn babies from mothers who are infected with CMV may also develop congenital CMV. It is estimated that one out of 200 infants is born with a congenital CMV infection.
CMV may cause serious disease in people with a weakened immune system, such as those with HIV or those taking medications that suppress the immune system. This virus can also cause other symptoms such as blurred vision, dysphagia, blindness, diarrhea, numbness in the legs, weakness, and pneumonia.
Risk Factors
Young children and adults who are in close contact with the following people are at risk of contracting CMV:
- Individuals who undergo blood transfusions
- Individuals who have received a mismatched organ that is CMV-infected
- Individuals who have undergone a bone marrow transplant
- Individuals with multiple sex partners
The following people may experience complications associated with CMV:
- Pregnant women
- People with a weakened immune system
- People with HIV/AIDS
- People who have undergone an organ transplant
- People diagnosed with cancer
- People who take medications that suppress the immune system
Transmission
Individuals who are infected with CMV may pass the virus through their body fluids, such as their saliva, tears, urine, semen, blood, or breast milk. The virus is spread through the following modes of transmission:
- Sexual contact
- Blood transfusions
- Organ transplant
- Breast milk
- Direct exposure or contact with an infected person’s saliva (kissing) or urine
CMV is usually present in an infected person's body fluids for months and at irregular intervals throughout his or her life, especially when the person has an impaired immune system due to disease (e.g., HIV/AIDS) or undergoes treatment (e.g., chemotherapy).
CMV can also be transmitted during gestation through the placenta from pregnant women's blood or from their vaginal secretions at childbirth. When it happens, newborns develop a condition called congenital CMV infection. Around 1-7 percent of women will develop their first CMV infection during pregnancy, and nearly one-third of them will pass the infection to their babies.
After childbirth, CMV can also be transmitted to babies through breastfeeding. However, babies can still continue breastfeeding unless they are prematurely born or when the doctor highly recommends avoiding breast milk. To help lower the risk of viral transmission, breast milk can be frozen and pasteurized. However, it does not in any way eliminate the virus.
Incubation Period
The incubation period, which is the period between CMV exposure and the time when the initial symptoms develop, ranges from 3-12 weeks in documented CMV infections and infected blood transfusion cases. CMV infections are not routinely screened because most of the time, such infections are benign. Moreover, CMV tends to be intermittently shed for a long period of time. For this reason, it can be difficult to say the exact incubation period of the virus, especially when it comes to the most common modes transmission, such as direct contact with genital fluids, urine, or saliva.
Signs and Symptoms
Most healthy individuals who contract CMV do not know they are infected with the virus since the infection does not cause any symptoms. Even if they experience symptoms, most of them are mild and somewhat the same with other types of illnesses, such as fever, fatigue, sore throat, and swollen glands. CMV may also cause hepatitis or mononucleosis in few cases.
If left untreated, the virus may also affect other parts of the body and cause the following conditions:
- Eye floaters (small specks or blind spots in your field of vision)
- Vision problems such as blindness or blurry vision
- Abdominal pain
- Diarrhea
- Trouble swallowing
- Pain, numbness, or weakness in the sacral region, which makes it difficult to walk
CMV can also cause the following symptoms in rare cases:
For individuals who are HIV-positive, a CD4 count below 100 puts them at an increased risk of becoming sick due to CMV.
When it comes to congenital CMV, newborns are usually asymptomatic until later in life. Around 2 percent of infants born with congenital CMV develop deafness and other complications. Moreover, approximately 10 percent of them show some signs and symptoms of the illness, which may include:
- Preterm birth
- Low birth weight
- Jaundice
- Microcephaly
- Enlarged liver or spleen
- Skin rashes
- Seizures
- Pneumonia
Diagnosis
Most CMV infections are left undiagnosed since the virus causes little to no symptoms. The body may develop antibodies and they may stay in the body for the rest of the person’s life. To detect the antibodies, a blood test is done. Doctors can also order a biopsy, a procedure that involves collecting tissue samples or fluids from the spine, throat, or intestine. The samples collected are sent to the laboratory for further analysis.
In some cases, eye doctors may check if there is retinal inflammation. The changes caused by CMV to the patients' brain or lungs can be visualized through the help of imaging tests, such as the CT scan.
Treatment
In general, treatments are unnecessary for healthy individuals. Most healthy adults who contract infectious mononucleosis due to CMV usually recover without taking any medications. However, people with weakened immune systems and newborns need to be treated, especially when they show signs and symptoms of the infection. The prescribed treatment usually depends on the severity of the infection including the signs and symptoms. The most common treatments for CMV infections are antiviral medications, which can help slow down viral replication. Although these drugs can help ease the infection, they cannot completely get rid of the virus. These antiviral medications include:
Like any other drugs, these medications also have their corresponding side effects, which include:
- Neutropenia (having low levels of neutrophils, which is a type of WBC)
- Fatigue or tiredness due to anemia
- Nausea and vomiting
- Skin rash
- Kidney problems
- Low levels of testosterone
Prevention
Individuals who are HIV-positive and taking antiretroviral therapy can increase their CD4 count to have a stronger immune system. Taking these drugs can also help prevent retinitis from coming back.
Don't forget to wash your hands after being exposed to other people's urine, saliva, and other body fluids. When engaging in sexual activities, always use condoms even in oral sex. Moreover, if you need a blood transfusion, speak with your doctor regarding the risks of CMV transmission.
