Congenital herpes tied to lower developmental test scores in infants

(Medical Xpress)—Infants with congenital human herpesvirus-6 (HHV-6) infections are more likely to score lower on a 12-month mental development test, according to a new URMC study published in the journal Pediatrics.

The study, which assessed 299 newborns over their first year of life, showed that babies with congenital infection scored several points lower than those without the infection. Scores for the infected babies were similar to those exposed to lead or cocaine in the womb.

"It's not a lot. They were all within the normal range," said Mary Caserta, M.D., professor of pediatrics and infectious disease at URMC and the study's lead researcher. "But it's similar to what you see with exposure to other toxins. Will that difference go away as they get older? Maybe. Will it get worse as they get older? Maybe. It's worth looking into."

HHV-6 is one of eight herpes viruses that infect humans. Every human is infected with HHV-6, usually in the first two years of life, and the infection often presents with fever, sometimes accompanied by roseola-like symptoms.

But for a small portion of the population, the virus is integrated into a person's genetic chromosomes, which causes a parent to transmit it to their offspring while they are still in the womb—about 1 percent of newborns have already been infected with the virus congenitally.

The infants in the URMC study were given three intelligence tests. For the first two—the Fagan Test of Infant Intelligence and the Visual Expectation Paradigm—there was no difference in scores between the infected infants and the uninfected infants. But for the third, a comprehensive test called the Bayley Scales of Infant Development II, the infected infants scored four points lower than their counterparts.

Caserta developed the study with the late Caroline B. Hall, M.D., a longtime professor of pediatrics at URMC who spent her career studying HHV-6 and other viruses. Going forward, Caserta said she'd like to test older children who have been identified with learning or cognitive disabilities to see if their rate of congenital HHV-6 infection is higher than the rest of the population.

"If children with learning disabilities have a 5 percent rate of congenital infection with HHV-6, while the rest of the population is at 1 percent, then that could be a signal that these infants do continue to have progressive developmental difficulties as they get older," said Caserta. "We've got some preliminary data that says these differences do exist, and now, we need to take the next step."