Congenital CMV Tied to Increased Prevalence of Microcephaly

By Will Boggs MD

September 17, 2020

NEW YORK (Reuters Health) - Congenital cytomegalovirus (CMV) is associated with a markedly increased prevalence of microcephaly at birth, according to a database study.

"Congenital cytomegalovirus is an important cause of microcephaly in the United States," Chelsea J. Messinger of Harvard T. H. Chan School of Public Health, in Boston, told Reuters Health by email. "As opposed to epidemic infections like Zika virus, which received a great deal of public health and medical attention, CMV is highly prevalent in the United States and has been responsible for a large number of microcephaly cases in the United States in recent decades."

More than half of adults in the U.S. are infected with CMV by age 40 years, and between 1% and 4% of seronegative women have a primary infection in pregnancy that can be associated with vertical transmission rates as high as 30% to 40%. An estimated 0.4% to 0.5% of infants in the U.S. are born with congenital CMV, which can be associated with microcephaly and other adverse neurological outcomes.

Messinger and her colleagues used data from two large healthcare databases to evaluate the association between congenital CMV and the prevalence of microcephaly at birth in the U.S.

In the pooled group of more than 2 million pregnancies, the prevalence of diagnosed congenital CMV was 1.4 per 10,000 live births, and the pooled prevalence of microcephaly was 2.9 per 10,000 live births.

The pooled prevalence of microcephaly was 232 times higher in newborns with a congenital CMV diagnosis (655 per 10,000) than in those without a diagnosis of congenital CMV (2.8 per 10,000), the ressearchers report in JAMA Pediatrics.

Far more infants with a microcephaly diagnosis (1.9%) than without (0.02%) had a recorded CMV test. Among infants tested for CMV, the pooled prevalence of microcephaly was still many times higher in newborns with a congenital CMV diagnosis (2143 per 10,000) than in those without the diagnosis (129 per 10,000).

"The low frequency of CMV screening among live-born infants in the United States (0.02% overall) was surprising to us," Messinger said. "Although it is partially explained by the limitations of claims data, we confirmed with another large retrospective study in the United States that the percentage of newborns screened for CMV is below 1%. This suggests that CMV is not high on the list of priorities for clinicians in the United States."

After excluding infants diagnosed as small for gestational age and/or preterm (because of their higher likelihood of microcephaly), the pooled prevalence of microcephaly remained 327 times higher among infants with a congenital CMV diagnosis (476 per 10,000) than among those without one (1.5 per 10,000).

Among secondary outcomes, the prevalence of hearing loss, neonatal seizures, chorioretinitis, or eye abnormalities was higher among infants with a congenital CMV diagnosis (versus those without a congenital CMV diagnosis) and among infants with microcephaly (versus those without microcephaly).

"While our results do not speak to potential preventive measures, greater attention to CMV by physicians and public health officials may be warranted," Messinger concluded.

SOURCE: JAMA Pediatrics, online September 14, 2020.