CMV: The Hidden Viral Threat to Infant Health

During pregnancy, it can seem like you undergo endless tests that can provide both assurance and anxiety as you await results. But a virus not included in regular prenatal screenings is the leading cause of congenital and developmental disabilities in the United States.

This virus is called cytomegalovirus (CMV) infection. It's a type of herpes related to the viruses that cause chickenpox and infectious mononucleosis. It is the most common infectious cause of congenital disabilities for babies in America.

CMV is more common than congenital listeriosis, toxoplasmosis, Zika virus and SARS-CoV-2, the virus that causes COVID-19. And it's more common than many well-known genetic disorders, such as cystic fibrosis, Down syndrome and pediatric HIV/AIDS, according to the National CMV Foundation.

"These [CMV] diagnoses are devastating for families, affecting more than 6,000 babies per year," stated Kristen Hutchinson Spytek, M.A., president of the National CMV Foundation.

However, there are ways you can get informed, protect yourself and your baby, and intervene with the virus for better outcomes.

How CMV is spread

"CMV is ubiquitous and spreads from one person to another through direct or prolonged contact with bodily fluids, including saliva, urine, blood, tears, vaginal fluid, semen and breast milk," Spytek explained.

CMV spreads most commonly to a mother and her baby through other kids in daycare. Parents can contract it unknowingly through everyday actions, such as sharing food with their children.

Although as few as 13 percent to 22 percent of women in the U.S. have heard of CMV, by age 40, between 50 percent and 80 percent of American adults have had an infection of the virus. Some people may experience fever, tiredness and muscle aches, but many cases show no symptoms or clear warning signs.

Health effects of CMV

"A CMV infection may present as a cold or flu and is typically harmless to the general population," Spytek explained. "CMV can cause serious disease, however, for those with weakened immune systems or in babies infected with CMV before birth, referred to as congenital CMV infection."

At birth, 90 percent of babies born with congenital CMV do not show any visible symptoms of the virus. According to the National CMV Foundation, approximately 10 percent to 15 percent of these babies may experience hearing loss, which can occur at birth or later in life. By age 5, 30 percent of children have contracted the virus, usually with no lasting effects.

Once you have contracted CMV, the virus stays with you for life, and it can reactivate, according to the Centers for Disease Control and Prevention (CDC). You can also become infected with another strain of the same virus later in life.

Babies born with symptomatic congenital CMV may have congenital disabilities and long-term health problems. These conditions can include but are not limited to hearing loss, vision loss, cognitive deficits, autism, epilepsy, microcephaly and cerebral palsy. Brain, liver, spleen, lung and growth problems may also occur.

CMV screening and treatment

If you suspect you've been exposed to CMV before or during pregnancy, or you work closely with or care for young children, ask your doctor to run CMV IgM and IgG antibody tests as part of your routine labs.

"These tests are relatively inexpensive and covered by most insurance plans," Spytek said. "If you are diagnosed with CMV during pregnancy, your doctor should perform an amniocentesis to determine whether congenital CMV has passed to your unborn baby."

For newborn CMV screening, congenital CMV can be diagnosed by testing a newborn baby's saliva, urine or blood using polymerase chain reaction (PCR) testing. Ideally, these specimens are collected before 21 days of life to confirm a diagnosis of congenital CMV infection.

"After three weeks, it is hard to determine if the baby could have contracted the infection through nursing or by exposure to siblings or others who may be shedding, or passing, the virus," Spytek said.

A definitive diagnosis of congenital CMV may provide the family with an opportunity for antiviral therapy, focused medical surveillance and early intervention services.

A CMV vaccine is on the horizon

Basic hygiene practices are the most effective ways to help decrease the risk of CMV transmission, though they are not foolproof. Wash your hands thoroughly, kiss your child on the forehead rather than the mouth and avoid sharing food, drinks and utensils.

Soon, a vaccine may be the best line of defense. Researchers have been investigating various CMV vaccine candidates for more than 50 years, but the complexity and poor general awareness of the virus have made finding a suitable candidate difficult.

Moderna is conducting clinical trials to evaluate a potential CMV vaccine candidate. The company is leveraging the same mRNA platform used in its COVID-19 vaccine and combining six mRNAs into one vaccine called mRNA-1647.

"The hope [is] one day providing a potential preventive measure against the virus," explained Allison August, M.D., vice president of clinical development, infectious diseases at Moderna. "These mRNAs give our cells instructions to make viral proteins mimicking the natural CMV infection. These proteins can't cause an infection. Instead, they train our immune system to fight the virus."

Currently, mRNA-1647 is being evaluated in a phase III pivotal registration study known as CMVictory. The study is ongoing and continuing to enroll patients.

"We anticipate having preliminary results from the study as early as 2023, but it's too early to speculate on when the CMV vaccine candidate may be approved and authorized for use," August said.

Until then, education and awareness can also play critical roles in helping to turn the tide against CMV. For additional information on the virus and how to get involved in the clinical trial for the vaccine, women can visit Moderna's Now I Know CMV website.