Cytomegalovirus (CMV) is a common virus many individuals encounter. While often unnoticed, a “CMV negative” test result holds significant meaning. This article clarifies what being CMV negative signifies and why this status is relevant.
What is Cytomegalovirus (CMV)?
Cytomegalovirus (CMV) is a widespread virus belonging to the herpes family, similar to the viruses that cause cold sores or chickenpox. It is so common that more than half of adults in the United States have been infected with CMV by age 40. For most healthy individuals, CMV infection typically causes mild symptoms, such as a low-grade fever or fatigue, or no symptoms at all, making it go unnoticed.
Once a person is infected with CMV, the virus remains in their body for life, usually in a dormant or inactive state. The virus can spread through various bodily fluids, including saliva, urine, blood, tears, semen, and breast milk. Direct contact with these fluids, particularly from babies and young children who often shed the virus, is a common transmission route.
Meaning of a “CMV Negative” Result
A “CMV negative” result indicates an individual has not been previously infected with Cytomegalovirus, meaning their immune system has not produced antibodies against the virus. Tests typically look for these antibodies (IgG and IgM) in the blood. The absence of both confirms a CMV negative status, signifying no prior exposure or existing immunity. Thus, a CMV negative person is susceptible to acquiring the virus if exposed.
Why CMV Negative Status Matters
Being CMV negative carries specific implications where a primary CMV infection could pose substantial risks. This primarily involves vulnerable populations who may experience severe complications from a new CMV infection.
For pregnant individuals, being CMV negative means they are susceptible to a primary CMV infection during pregnancy, which can have significant consequences for the developing fetus. If a pregnant person acquires CMV for the first time, there is a risk of transmitting the virus to the baby, leading to a condition known as congenital CMV (cCMV). Congenital CMV can result in serious health problems for the baby, including hearing loss, vision impairment, developmental delays, and, in some cases, can be fatal. The highest risk to the unborn baby occurs when the primary infection happens during the first half of pregnancy.
In the context of blood transfusions, CMV negative blood products are important for certain immunocompromised patients. Premature infants, for example, have underdeveloped immune systems and are highly vulnerable to infections. Transfusing CMV-positive blood to these babies could lead to severe or even fatal CMV disease. Therefore, CMV negative blood is specifically requested for them, along with other severely ill or immunocompromised patients, such as organ or stem cell transplant recipients.
For individuals undergoing organ or stem cell transplantation, their CMV status and that of their donor are important factors. If a CMV negative recipient receives an organ or stem cells from a CMV positive donor, the risk of developing a serious CMV infection after transplantation is significantly elevated. Immunosuppressive medications taken by transplant recipients to prevent rejection further increase vulnerability. To mitigate these risks, healthcare teams often prefer CMV negative donors for CMV negative recipients or implement specific antiviral prophylactic measures if a CMV positive donor is used.
Strategies for Remaining CMV Negative
For CMV negative individuals, especially those in vulnerable groups like pregnant people or transplant candidates, adopting hygiene practices can reduce the risk of acquiring the virus. These strategies focus on minimizing contact with bodily fluids where CMV is commonly shed.
Frequent and thorough handwashing with soap and water is an important measure, especially after changing diapers, wiping a child’s nose or mouth, or handling children’s toys. Avoiding the sharing of food, drinks, utensils, or pacifiers with young children can also help prevent transmission. Additionally, instead of kissing young children on the lips, kissing them on the forehead can reduce exposure to saliva. While not all CMV infections can be prevented, these practical steps can lower the chance of acquiring the virus.