Infants under 3 months old who test positive for COVID-19 tend to do well, mostly showing only a fever and few respiratory symptoms, a new study reveals.

The study, which included 18 infants, showed that out of the 50 percent who were admitted to a hospital's general inpatient service, none required oxygen, respiratory support, or intensive care.

"While there is limited data on infants with COVID-19 from the United States, our findings suggest that these babies mostly have mild illness and may not be at higher risk of severe disease as initially reported from China." said lead author Leena B. Mithal, pediatric infectious diseases expert from Lurie Children's Hospital and assistant professor of pediatrics at Northwestern University Feinberg School of Medicine, in a statement.

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A new study revealed that babies under 90 days old with COVID-19 experienced more mild symptoms. (iStock)

"Most of the infants in our study had fever, which suggests that for young infants being evaluated because of fever, COVID-19 may be an important cause, particularly in a region with widespread community activity. However, evaluation for bacterial infection in young infants with fever remains important," Mithal said.

Out of the infants admitted to the hospital, six out of nine had gastrointestinal symptoms, such as poor feeding, vomiting and diarrhea. Upper respiratory tract symptoms of cough and congestion preceded onset of GI symptoms, researchers said. Young infants also had notably high viral loads in their nasal specimens despite mild clinical illness.

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"It is unclear whether young infants with fever and a positive test for SARS-CoV-2 require hospital admission," explained Mithal. "The decision to admit to the hospital is based on age, need for preemptive treatment of bacterial infection, clinical assessment, feeding tolerance, and adequacy of follow-up. There may be opportunities to utilize rapid SARS-CoV-2 testing to determine disposition of clinically well infants with fever."

According to Mithal and their colleagues, there was an overrepresentation of Latinx ethnicity among their sample of infants at 78 percent.

"Although we expected that there would be many infants of Latinx ethnicity with COVID-19, there may be additional factors contributing to the disproportionate majority of Latinx cases we observed in this age group," said Mithal. "Access to sick-visit care in some primary care pediatric offices has been limited, with practices referring symptomatic children to the emergency department. Limited access to telemedicine care also may be a factor. Finally, there may be a greater likelihood of exposure with extended family living in the home or family members working outside the home during this pandemic."

Findings were published in The Journal of Pediatrics.