A MOUSE long COVID model associates breathlessness with postinfectious fibrotic lung remodeling and neuroinflammation following clearance.
In this head-to-head study, investigators tracked subchronic organ changes after sublethal infection with mouse adapted SARS-CoV-2 (MA30) or influenza A (PR8) in adult C57BL/6 mice, following animals out to 28 days post infection. While both infections produced severe acute illness with notable weight loss, surviving mice largely regained weight by the end of follow up, highlighting that clinical recovery can occur alongside ongoing tissue injury.
Long COVID and Persistent Respiratory Sequelae
Both viruses produced prolonged lung inflammation and collagen deposition through 28 days, consistent with a subchronic course of inflammatory lung injury and fibrotic remodeling. The key difference was the pattern of recovery. PR8 infection showed features consistent with epithelial regeneration, including persistence of basal epithelial markers and evidence that repair programs were engaged. In contrast, MA30 infection was characterized by sustained activation of inflammatory, complement, and coagulation associated programs alongside extracellular matrix remodeling, with signals consistent with continued barrier dysfunction rather than restoration.
For clinicians, this divergence supports a practical hypothesis: post viral dyspnea may not reflect a single pathway. The influenza like trajectory in this model aligns with repair dominant recovery, whereas the SARS-CoV-2 trajectory aligns with persistent inflammation, vascular linked signaling, and remodeling. If similar patterns hold in people, it could help explain why some patients experience prolonged breathlessness after SARS-CoV-2 even when viral burden is no longer detectable.
Neuro Symptoms Without Brain Infection
Neither infection produced detectable brain infection, yet MA30 infection uniquely increased microhemorrhage frequency early after infection and drove persistent neuroinflammation across all timepoints. Brain profiling in MA30 animals showed enrichment of pathways consistent with vascular dysfunction, extracellular matrix remodeling, and IL-6 related signaling, alongside virus specific disruption of hypothalamic pituitary axis programs that was not seen with PR8.
Together, the findings suggest that long COVID relevant neurological symptoms could arise from inflammatory and microvascular mechanisms rather than direct neuroinvasion, and they reinforce the need to monitor neurocognitive and neuropsychiatric complaints in patients after SARS-CoV-2 infection even when acute disease has resolved.
Reference: Currey J et al. Characterization of subchronic lung and brain consequences caused by mouse-adapted SARS-CoV-2 and influenza A infection of C57BL6 mice. Frontiers in Immunology. 2026;DOI:10.3389/fimmu.2026.1755141.
