Differentials
Coronavirus disease 2019 (COVID-19)
SIGNS / SYMPTOMS
Residence in/travel to a country/area or territory with local transmission, or close contact with a confirmed or probable case of COVID-19, in the 14 days prior to symptom onset.
Initial signs and symptoms are similar so it may be difficult to differentiate between the conditions clinically.
INVESTIGATIONS
COVID-19 antigen test or real-time reverse transcription polymerase chain reaction (RT-PCR): positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA.
It is not possible to differentiate COVID-19 from other causes of pneumonia on chest imaging alone.
Typical bacterial pneumonia
SIGNS / SYMPTOMS
Acute onset with a chill followed by a high fever and pleuritic chest pain suggests pneumococcal pneumonia.
INVESTIGATIONS
Sputum cultures and blood cultures may be positive for Streptococcus pneumoniae or other bacterial pathogens.
Viral pneumonia
SIGNS / SYMPTOMS
Lack of effectiveness of antibiotics.
INVESTIGATIONS
Positive nasopharyngeal viral diagnostics; relative lymphocytosis in WBC count.
Tuberculosis
SIGNS / SYMPTOMS
History of immunosuppression or prolonged course of disease that is not responding to antibacterial therapy.
INVESTIGATIONS
Sputum cultures and acid-fast bacillus stain positive; cavity on chest x-ray.
Pneumocystis jiroveci pneumonia
SIGNS / SYMPTOMS
History or risk factors for HIV infection.
INVESTIGATIONS
Special stain of sputum or bronchoalveolar lavage positive for Pneumocystis jiroveci.
Pulmonary embolism
SIGNS / SYMPTOMS
Absence of fever and/or lack of response to antimicrobial therapy.
INVESTIGATIONS
CT pulmonary angiography may demonstrate pulmonary embolism.
Inhalation/occupational lung injury
SIGNS / SYMPTOMS
History of an exposure to chemicals or special work conditions.
INVESTIGATIONS
Negative cultures; diffuse disease on chest x-ray.
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