One day last February, after rounds at the Johns Hopkins Children’s Center, Ravit Boger was on her way home when she received an urgent call to return. A couple who had vacationed in a Zika virus-affected country learned that their newborn had an abnormal brain ultrasound. The mother had a flulike illness during pregnancy.

Boger, a pediatric infectious diseases specialist, recalls the mother’s panic when they met. But after examining the baby, she explained to the parents that their baby probably didn’t have Zika. That’s because in almost every case presenting with similar symptoms, cytomegalovirus (CMV) is the culprit. Still, erring on the side of caution, Boger ordered blood work for Zika, as well as CMV and other congenital infections.

Two days later, test results came back positive for CMV. The parents were concerned to learn about a new virus and its impact on the baby’s hearing and brain development—potential effects Boger had already explained to them. They wondered aloud, “How is it possible that an educated couple like us has never heard of CMV?”

The comment gave Boger pause. “It was a wake-up call to me in the midst of the Zika publicity that CMV is largely unknown,” she says.

Yet, roughly one of every 150 newborns in the U.S. is born with CMV. It’s the most common congenital infection in the nation. A member of the herpes viruses, cytomegalovirus is usually harmless, says Boger. However, when transmitted during pregnancy, about one in 10 will develop permanent problems with hearing or learning. Though symptoms may not be apparent at birth, they can surface over time.

CMV also causes serious complications in people with weakened immune systems, particularly in patients receiving organ or bone marrow transplants.

Boger says that although almost everyone is exposed to the virus, it typically remains dormant and harmless. “As we age,” she explains, “80 to 90 percent of us will have developed antibodies to CMV.” Indeed, most healthy children and adults infected with CMV don’t even know it because symptoms are mild—low-grade fever and swollen glands.

But reactivation or getting infected with a new strain of CMV during pregnancy is potentially harmful to the fetus and newborn. The virus can be spread by close contact with a person who has the virus in his or her saliva, urine or other body fluids.

Once a baby is diagnosed after birth, CMV requires treatment to lower the risk of long-term consequences. Currently, intravenous ganciclovir or oral valganciclovir are the primary antiviral treatments for CMV. The drugs suppress the virus, says Boger, but they can’t eliminate it. In the absence of vaccine for CMV, the best form of prevention is hand-washing.

“Some infected newborns are never diagnosed with CMV or are diagnosed late, when they already have hearing loss,” says Boger. “If we could diagnose earlier, it would be helpful because we have treatment that does have some impact. Though they have side effects, they’ve been shown to prevent progression of hearing loss.”

Boger, an almost 20-year Johns Hopkins veteran, is working with colleagues in her CMV lab to better understand how the virus works and how it can be inhibited. She is hopeful about developing a more targeted combination therapy to effectively suppress the virus.

Still, it troubles Boger that no federally mandated screening program exists to detect CMV in newborns. Although the test is relatively inexpensive—$50 to $100—and parents may request it, most don’t know about CMV. Meanwhile, she says, “If we can raise awareness about CMV’s hazards and the need for greater funding, it will go a long way to help develop better treatments —and hopefully, a vaccine.”