Human Cytomegalovirus- An Overview


Human cytomegalovirus (HCMV) is a common virus that belongs to the herpesvirus family, also known as human herpesvirus-5 (HHV-5) . It is estimated that 50% to 80% of adults in the United States have been infected with HCMV by the age of 40 . Most people who are infected with HCMV do not have any symptoms or health problems, because their immune system can control the virus. However, HCMV can cause serious disease and complications in some people, especially those who have weakened immune systems, such as organ transplant recipients, cancer patients, HIV/AIDS patients, and newborns who are infected before or during birth .

HCMV is transmitted through direct contact with bodily fluids, such as saliva, urine, blood, breast milk, semen, and cervical secretions . The virus can also cross the placenta and infect the fetus during pregnancy . HCMV can remain latent in the body for life, meaning that it can stay dormant in certain cells without causing any symptoms. However, the virus can reactivate and cause disease when the immune system is suppressed or impaired by stress, illness, medication, or aging .

HCMV infection can affect various organs and systems in the body, such as the eyes, lungs, liver, brain, gastrointestinal tract, and blood cells . The signs and symptoms of HCMV infection depend on the age and immune status of the person infected. In healthy adults and children, HCMV infection may cause mild or no symptoms at all. Some people may experience a flu-like illness or a mononucleosis-like syndrome with fever, fatigue, sore throat, swollen glands, and muscle aches . In immunocompromised individuals, HCMV infection can cause severe and life-threatening complications, such as pneumonia, retinitis (inflammation of the retina that can lead to blindness), hepatitis (inflammation of the liver), colitis (inflammation of the colon), esophagitis (inflammation of the esophagus), encephalitis (inflammation of the brain), and sepsis (a systemic inflammatory response to infection) . In congenital HCMV infection, which occurs when a pregnant woman passes the virus to her fetus, the baby may be born with symptoms such as jaundice (yellowing of the skin and eyes), rash, low birth weight, microcephaly (small head size), seizures, hearing loss, mental retardation, and developmental delays .

The diagnosis of HCMV infection is based on clinical features and laboratory tests. The laboratory tests include virus isolation from body fluids or tissues using cell culture or animal inoculation; detection of viral antigens or nucleic acids using immunofluorescence assay (IFA), enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), or nucleic acid sequence-based amplification (NASBA); and detection of antibodies against HCMV using complement fixation test (CFT), ELISA, IFA, or radioimmunoassay (RIA) . The treatment of HCMV infection depends on the severity and type of disease. Antiviral drugs such as ganciclovir, foscarnet, cidofovir, and valganciclovir are used to inhibit viral replication and reduce viral load. However, these drugs are not curative and may have side effects and toxicity. Therefore, they are reserved for patients with severe or life-threatening disease or those at high risk of complications. Supportive care such as hydration, nutrition, oxygen therapy, blood transfusion, and pain management may also be needed. The prevention and control of HCMV infection include screening of blood donors and organ donors for HCMV antibodies; administration of immunoglobulin or antiviral prophylaxis to high-risk patients; hygiene measures such as hand washing and avoiding contact with bodily fluids; education and counseling of pregnant women about the risks of congenital HCMV infection; and development of vaccines against HCMV .

HCMV is a ubiquitous virus that can cause a wide spectrum of clinical manifestations in humans. It is important to recognize the risk factors, signs and symptoms, diagnosis methods, treatment options, and prevention strategies for HCMV infection in order to reduce morbidity and mortality associated with this virus.