Definition of Cytomegalovirus (CMV)

Cytomegalovirus (CMV) is a virus that affects between 50% and 85% of adults in the United States by the time they reach 40 years old. It is the most commonly transmitted virus to a child before birth. Those who show symptoms often experience a flu-like condition with an extended fever and mild symptoms. Once infected, the virus remains in the person's body for life, usually lying dormant. The disease typically manifests only when the immune system is weakened by medication or illness. CMV is particularly concerning due to the risk it poses to unborn babies, individuals working with children, and those with weakened immune systems, such as transplant recipients.CMV is part of the herpesvirus family, which also includes herpes simplex virus, varicella-zoster virus (responsible for chickenpox), and Epstein-Barr virus (which causes infectious mononucleosis). These viruses share the characteristic of lying dormant within the body for extended periods. Initial CMV infection may present few symptoms, but it is always followed by a long, unnoticed phase where the virus resides in cells without causing apparent harm or illness. A severely impaired immune system, whether due to medication or disease, can reactivate the virus from its dormant state.The virus can be shed through bodily fluids of any previously infected person and may be found in urine, saliva, blood, tears, semen, and breast milk. Shedding can occur intermittently without visible signs or symptoms. CMV is spread through person-to-person contact, requiring close interaction with someone excreting the virus in their bodily fluids. It can be transmitted sexually, through breast milk, organ transplants, and, though rarely, via blood transfusions. Despite not being highly contagious, CMV can spread within households and among young children in daycare centers.Transmission can often be prevented since it's mainly spread through contact with infected bodily fluids that touch hands and are later absorbed through the nose or mouth. Proper hygiene, such as washing hands with soap and water, is effective in removing the virus. CMV infection without symptoms is common in infants and young children, so excluding an infected child from school or institutional settings is unnecessary. Similarly, hospitalized patients don't require special isolation precautions.If a woman contracts CMV during pregnancy, there's a risk of the baby being born with CMV and experiencing related complications. However, infants and children who contract CMV after birth usually show few, if any, symptoms or complications. CMV is the leading cause of congenital infections in the US. For infants infected before birth, outcomes may vary: they might experience mild to severe symptoms, such as liver and spleen enlargement, or even fatal illness. With supportive care, most infants survive, but 80% to 90% may face complications like hearing loss, vision impairment, and developmental delays. Another 5% to 10% of infected infants show no symptoms at birth but may later develop hearing, mental, or coordination issues.Most healthy individuals working with children don't face significant risks from CMV infection. However, women of childbearing age who haven't been previously infected with CMV could pose a risk to their unborn child if exposed. Contact with young children in daycare settings, where CMV is commonly spread, can be a source of exposure. Since CMV spreads through infected body fluids like urine and saliva, child care providers should be informed about CMV risks and precautions. Daycare workers may face higher risks than healthcare providers, possibly due to the emphasis on hygiene in medical settings.For patients with primary CMV infection, serious disease can develop, but the common issue is reactivation of the dormant virus. CMV is a major cause of illness and death in immunocompromised patients, including organ transplant recipients and those undergoing chemotherapy or receiving immunosuppressive drugs, as well as HIV-positive individuals. Common complications include retinitis and gastrointestinal disease. To reduce risk, exposure of immunocompromised patients to CMV should be minimized. When possible, CMV-negative organs or blood products should be used.Most CMV infections go undiagnosed because the virus rarely causes symptoms and reactivates without noticeable signs. However, those who have been infected develop antibodies that remain in the body for life. Various laboratory tests have been developed to detect these antibodies, confirming infection. Additionally, the virus can be cultured from samples like urine, throat swabs, and tissue to identify active infections.