Historically, plain film (x-ray) radiography and computed tomography (CT) have been useful for clinical assessments of influenza disease severity in clinical cases [25, 26] . These imaging modalities are limited by characterizing only anatomic changes in the lung parenchyma, such as ground-glass opacity (GGO) and consolidations, which represent different degrees of interstitial and alveolar filling by cells, edema, and inflammatory exudate [27] . In contrast, positron emission tomography (PET) imaging with the radiotracer, [ 18 F]-2-fluoro-2-deoxy-D-glucose ([ 18 F]-FDG), can provide data on metabolic activity of cells by measuring sites of increased glycolysis from leukocyte chemotaxis and accumulation, and provide increased sensitivity in detection of cells during inflammation. [ 18 F]-FDG, an analog of glucose that is moved into cells via facilitated transport, is commonly used in PET imaging as a radiotracer in clinical and basic science research. Recent studies have demonstrated the utility of the [ 18 F]-FDG in assessment of infectious disease burden in animal models of schistosomiasis and tuberculosis [28] [29] [30] . PET/CT has been used in the assessment of one hospitalized H1N1pdm patient and revealed an intense inflammatory response [31] . The uptake of [ 18 F]-FDG in humans and animals suggests the predominant presence of activated neutrophils [32] [33] [34] [35] . In studies of mice infected with influenza A virus, neutrophils play a critical role in protection and recovery from infection, and participate in the process of adaptive immunity to the virus [36] . Coupled with molecular virology and pathology, molecular imaging with important probes of disease has enormous potential to reveal early critical factors that contribute to the clinical progression of illness as well as accelerate screening, the efficacy and mechanistic studies of vaccines and antiviral therapies [17, 18] .