Febrile Young Infants Less than 120 Days Old in the Post-COVID-19 Pandemic Era: Sterile Pyuria or Urinary Tract Infection?

J Microbiol Immunol Infect. 2025 May 8:S1684-1182(25)00087-8. doi: 10.1016/j.jmii.2025.04.006. Online ahead of print.

Abstract

Background: After the Coronavirus Disease 2019 (COVID-19) outbreak, there was an increasing number of febrile young infants concurrent with COVID-19. Urinary tract infection (UTI) is an important source of severe bacterial infections in febrile young infants. Accurate data on the incidence of pyuria and UTI in febrile young infants with or without COVID-19 in the post-pandemic period remains unclear.

Methods: We conducted a retrospective analysis of clinical and laboratory data from febrile young infants less than 120 days old, admitted to the Sick Baby Room of a tertiary referral hospital in Taiwan, between March 1, 2023, and February 29, 2024. These infants underwent COVID-19 testing either in the emergency department or during hospitalization.

Results: Among the 265 febrile young infants who underwent COVID-19 testing, 124 (46.8 %) tested positive. Infants with COVID-19 had a significantly lower incidence of UTI compared with those testing negative [10/124 (8.1 %) vs 47/141 (33.3 %), p < 0.001]. The incidence of sterile pyuria was relatively high in the COVID-19 positive group compared with those testing negative [45/124 (36.3 %) vs 33/141 (23.4 %), p = 0.022]. Among those with COVID-19, more patients with sterile pyuria were exposed to antibiotics than those without pyuria [12/45 (26.7 %) vs 6/69 (8.6 %), p = 0.010].

Conclusion: In febrile young infants with COVID-19, the incidence of pyuria is high, but the occurrence of definite UTI was low compared with those without COVID-19. Routine empirical antibiotic administration in febrile young infants concurrent with COVID-19 may not be necessary. These findings highlight the importance of cautious antibiotic prescribing practices in this population.

Keywords: COVID-19; Pyuria; Urinary tract infection.