High transaminase levels may flag severe flu in hospitalized children

A routine blood test used in many hospitals may help identify which children hospitalized with influenza are most likely to worsen. In a multicentre retrospective cohort study of 543 children admitted with acute viral respiratory infections, elevated transaminases tracked with more severe disease, systemic complications, intensive care admission and worse outcomes.

The study, published in July 2026 in Influenza and Other Respiratory Viruses, included 127 children with laboratory-confirmed influenza. Among those flu cases, 24.4% had elevated transaminases, compared with 7.2% of children hospitalized with noninfluenza respiratory infections. The study concluded that the enzyme rise likely reflected systemic and muscular involvement rather than primary liver injury.

Transaminases are liver enzymes, but a rise can also signal broader tissue stress elsewhere in the body. In children who look routine at first and then deteriorate quickly, the marker adds another layer to existing bedside assessment, especially because the test is already part of standard hospital lab panels.

The signal was not uniform across flu types. The study found hypertransaminasemia was more common with influenza B than influenza A. Age, respiratory status, oxygen needs, dehydration and underlying conditions still need to drive care decisions.

CDC surveillance has estimated that seasonal influenza causes 100,000 to 710,000 hospitalizations a year in the United States, and FluSurv-NET has tracked laboratory-confirmed influenza-associated hospitalizations since 2003.

A Pediatrics study found antiviral use in hospitalized children dropped to 38.1% in 2021 to 2022 and 46.1% in 2022 to 2023, down from 48.3% to 56.8% before the pandemic. The American Academy of Pediatrics still recommends prompt antiviral treatment for children hospitalized with suspected or confirmed influenza, including those with severe or progressive illness.