In a research letter today in JAMA Pediatrics, Chinese researchers say that they can't rule out mother-to-baby COVID-19 transmission in three infected newborns, indicating the need for increased vigilance before and after delivery.

Meanwhile, an observational cohort study yesterday in The Lancet Infectious Diseases presents evidence that children may be more likely than adults to spread coronavirus because their often-asymptomatic illness makes infections harder to identify.

Mother-infant spread possible in 3 cases

The JAMA letter details a cohort study of 33 newborns of women with COVID-19–related pneumonia in Wuhan, China. Three (9%) of the newborns had coronavirus-related pneumonia on chest x-ray but later recovered.

"Because strict infection control and prevention procedures were implemented during the delivery, it is likely that the sources of SARS-CoV-2 in the neonates' upper respiratory tracts or anuses were maternal in origin," the authors wrote, referring to the coronavirus that causes COVID-19. "Although … all samples, including amniotic fluid, cord blood, and breast milk, were negative for SARS-CoV-2, the vertical maternal-fetal transmission cannot be ruled out in the current cohort."

The first baby was born at normal gestation by cesarean delivery because of meconium-stained amniotic fluid and maternal pneumonia. The next day, the baby developed lethargy and fever. Nose-throat and anal swabs were positive on days 2 and 4 of life but negative by day 6.

The second baby, born by cesarean delivery at normal gestation because of maternal pneumonia, had lethargy, vomiting, and fever. Lab tests indicated leukocytosis (elevated white blood cell count), lymphocytopenia (low lymphocytes in the blood), and high levels of creatine kinase MB (an enzyme primarily found in heart muscle cells). As with the first baby, nose-throat and anal swabs were positive on days 2 and 4 of life but negative by day 6.

The third baby, born 9 weeks prematurely by cesarean delivery because of fetal distress and maternal pneumonia, needed resuscitation. He had neonatal respiratory distress syndrome, an Enterobacter agglomerates-positive blood culture indicating sepsis, leukocytosis, thrombocytopenia (low platelet count), and an inability to form blood clots.

He recovered after receiving noninvasive ventilation, caffeine, and antibiotics for 14 days. Nose-throat and anal swabs were positive on days 2 and 4 but negative by day 7.

Although all had relatively mild COVID-19 symptoms and good outcomes, "It is crucial to screen pregnant women and implement strict infection control measures, quarantine of infected mothers, and close monitoring of neonates at risk of COVID-19," the researchers said.

Kids with mild or no symptoms may spread virus

In the Lancet study, scientists used the electronic health records of 36 children 0 to 16 years old with confirmed COVID-19 infection at three hospitals in Zhejiang, China, from Jan 17 to Mar 1 to identify epidemiologic and clinical features of the disease.

The children (mean age, 8.3 years; standard deviation [SD], 3.5) became infected after close contact with family members (32, 89%) or exposure to the endemic area (12, 33%). Eight patients had both types of exposures.

Nineteen (53%) of the children had moderate illness and pneumonia, while 17 (47%) had mild illness and either no symptoms (10, 28%) or upper respiratory symptoms (7, 19%).

"Although all paediatric patients in our cohort had mild or moderate type of COVID-19, the large proportion of asymptomatic children indicates the difficulty in identifying paediatric patients who do not have clear epidemiological information, leading to a dangerous situation in community-acquired infections," the authors wrote.

In a commentary in the same journal, Alyson Kelvin, PhD, and Scott Halperin, MD, of Dalhousie University in Canada, called for further research into children's role in coronavirus transmission. "If children are important in viral transmission and amplification, social and public health policies (eg, avoiding interaction with elderly people) could be established to slow transmission and protect vulnerable populations," they said.

At hospitalization, common symptoms included fever (13, 36%) and dry cough (7, 19%). Four patients (11%) with fever had a temperature of at least 101.3°F, while 9 (25%) had a temperature of 99.5° to 101.3°F.

Abnormal laboratory findings included elevated creatine kinase MB (11, 31%), low lymphocyte levels (11, 31%), leukopenia (low white cell count; 7, 19%), and high procalcitonin levels (6, 17%). Decreased lymphocytes, high body temperature, and high levels of procalcitonin, D-dimer, and creatine kinase MB were significantly linked to severe disease.

All children were treated with aerosolized interferon alfa twice daily, while 14 (39%) received lopinavir-ritonavir syrup twice daily, and six (17%) received supplemental oxygen. Mean length of hospitalization was 14 days (SD, 3), and all patients recovered.