Differentials

SIGNS / SYMPTOMS
INVESTIGATIONS
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. 

Signs and symptoms are similar so it may be difficult to differentiate between the conditions clinically. The situation is evolving rapidly; see our COVID-19 topic for further information.

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Real-time reverse transcription polymerase chain reaction (RT-PCR): positive for SARS-CoV-2 RNA.

It is not possible to differentiate COVID-19 from other causes of pneumonia on chest imaging.

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

Acute onset with a chill followed by a high fever and pleuritic chest pain suggests pneumococcal pneumonia.

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Sputum cultures and blood cultures may be positive for Streptococcus pneumoniae or other bacterial pathogens.

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

Symptoms of dry cough, fever, myalgia, and malaise, which are clinically difficult to differentiate from atypical bacterial pneumonia.

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Nasopharyngeal viral cultures may be positive. Relative lymphocytosis on CBC may be detected.

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

A history of immunosuppression or prolonged course that is not responding to antibacterial therapy suggests tuberculosis.

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Sputum cultures and acid fast bacilli stains positive. A cavity on the chest x-ray may be observed.

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

Travel or exposure in endemic area.

There may be extrapulmonary symptoms (e.g., rheumatologic).

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Sputum culture and stain may demonstrate hyphae or yeasts.

Antigen detection assays or polymerase chain reaction may identify specific mycoses (e.g., aspergillosis).

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

History of HIV or risk factors should raise suspicion.

INVESTIGATIONS

Special stain of sputum or bronchoalveolar lavage will be positive for Pneumocystis jirovecii.

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

Absence of fever and/or lack of response to antimicrobial therapy support a diagnosis of pulmonary embolism.

INVESTIGATIONS

The ventilation-perfusion scan will be positive in pulmonary embolism.

SIGNS / SYMPTOMS
INVESTIGATIONS
SIGNS / SYMPTOMS

A history of exposure to chemicals or special work conditions should raise suspicion of inhalation/occupational lung injury.

INVESTIGATIONS

Cultures will be negative. There may be diffuse disease on the chest x-ray.

SIGNS / SYMPTOMS
INVESTIGATIONS
SIGNS / SYMPTOMS

Course of disease may be rapid with respiratory problems; might present with mediastinal masses. Clusters of cases may occur.

INVESTIGATIONS

Cultures will be positive for Bacillus anthracis. Mediastinal widening may present in the respiratory forms of the disease.

SIGNS / SYMPTOMS
INVESTIGATIONS
SIGNS / SYMPTOMS

Course of disease may be rapid with respiratory problems; might present with mediastinal masses. Clusters of cases may occur.

INVESTIGATIONS

Cultures will be positive for Yersinia pestis. Chest x-ray will show unilateral or bilateral consolidation or alveolar infiltrates.

SIGNS / SYMPTOMS
INVESTIGATIONS
SIGNS / SYMPTOMS

Course of disease may be rapid with respiratory problems; might present with mediastinal masses. Clusters of cases may occur.

INVESTIGATIONS

Cultures will be positive for Francisella tularensis. Hilar adenopathy may present in the respiratory forms of the disease.

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