Differential Diagnosis for Shortness of Breath with Intermittent Fever

Primary Infectious Differentials

The American Thoracic Society suggests that viral pneumonias, including COVID-19 and influenza, should be prioritized given the clinical presentation of dyspnea and fever without prominent cough, which can occur in 10-20% of cases 2, 4
The Infectious Diseases Society of America recommends distinguishing other viral pneumonias, including influenza A/B, parainfluenza virus, adenovirus, respiratory syncytial virus, rhinovirus, and human metapneumovirus, from COVID-19 1, 3, 5
The absence of cough does not exclude viral pneumonia, as some patients present with predominantly systemic symptoms, such as fever and dyspnea, without respiratory tract symptoms 2, 6

The American College of Chest Physicians states that pulmonary embolism must be aggressively excluded in any patient with subacute dyspnea, particularly when symptoms are slow to respond or worsen 3
The European Respiratory Society suggests that organizing pneumonia and vasculitis should be distinguished from infectious causes, particularly with prolonged symptoms 1, 3, 5

The American College of Radiology recommends chest radiography as the initial test to identify consolidations, ground-glass opacities, or alternative pathology 2, 7
The Society of Critical Care Medicine suggests that complete blood count with differential, inflammatory markers, and respiratory pathogen panel, including COVID-19 RT-PCR, should be obtained 1, 2, 3

The American Thoracic Society recommends checking oxygen saturation, assessing respiratory rate, and evaluating for red flags, such as persistent hypotension, altered mental status, or respiratory distress, to determine the severity of disease 4, 2, 8
The Infectious Diseases Society of America suggests obtaining CBC with differential, CRP, procalcitonin, and respiratory viral panel, including COVID-19 RT-PCR, as initial testing 1, 2, 3

The American College of Chest Physicians warns against dismissing pulmonary embolism based solely on the absence of classic symptoms, as pneumonia can mask PE, particularly when fever predominates 2, 6
The European Respiratory Society advises against relying on a single negative test, as COVID-19 RT-PCR has false negatives, and multiple samples from different sites increase diagnostic yield 1, 3