Differentials
Coronavirus disease 2019 (COVID-19)
SIGNS / SYMPTOMS
Important to consider the current epidemiological situation. May give history of unwell contacts.
Signs and symptoms are similar so it may be difficult to differentiate between the conditions clinically.
INVESTIGATIONS
Real-time reverse transcription polymerase chain reaction (RT-PCR): positive for SARS-CoV-2 RNA. Rapid antigen tests may also be used.
It is not possible to differentiate COVID-19 from other causes of pneumonia on chest imaging.
Severe acute respiratory syndrome (SARS)
SIGNS / SYMPTOMS
Lack of travel history to or from the Middle East (or country where there is an ongoing outbreak) in the preceding 14 days.
No close contact with a symptomatic traveller from the Middle East or a suspected or confirmed case of MERS in the preceding 14 days.
Patients with severe disease have a lower incidence of comorbidities compared with MERS.
Clinical features are similar; however, patients are less likely to present with haemoptysis (1% of patients with SARS) or dyspnoea (42% of patients with SARS).[8]
Usually less aggressive than MERS as reflected by the lower mortality rate.[85]
Common cold
SIGNS / SYMPTOMS
Lack of travel history to or from the Middle East (or country where there is an ongoing outbreak) in the preceding 14 days.
No close contact with a symptomatic traveller from the Middle East or a suspected or confirmed case of MERS in the preceding 14 days.
Seasonal outbreak during winter.
Differentiating MERS from community-acquired respiratory tract infections is not possible from signs and symptoms.
INVESTIGATIONS
RT-PCR: negative for MERS-CoV RNA.
Influenza infection
SIGNS / SYMPTOMS
Lack of travel history to or from the Middle East (or country where there is an ongoing outbreak) in the preceding 14 days.
No close contact with a symptomatic traveller from the Middle East or a suspected or confirmed case of MERS in the preceding 14 days.
Seasonal outbreak during winter.
Differentiating MERS from community-acquired respiratory tract infections is not possible from signs and symptoms.
INVESTIGATIONS
RT-PCR: positive for influenza A or B viral RNA.
Avian influenza A (H5N1) virus infection
SIGNS / SYMPTOMS
Lack of travel history to or from the Middle East (or country where there is an ongoing outbreak) in the preceding 14 days.
No close contact with a symptomatic traveller from the Middle East or a suspected or confirmed case of MERS in the preceding 14 days.
Close contact with infected birds (e.g., farmer or visitor to a live market in endemic areas) or living in an area where avian influenza is endemic.
Differentiating MERS from community-acquired respiratory tract infections is not possible from signs and symptoms.
INVESTIGATIONS
RT-PCR: positive for H5N1 viral RNA.
Avian influenza A (H7N9) virus infection
SIGNS / SYMPTOMS
Lack of travel history to or from the Middle East (or country where there is an ongoing outbreak) in the preceding 14 days.
No close contact with a symptomatic traveller from the Middle East or a suspected or confirmed case of MERS in the preceding 14 days.
Close contact with infected birds (e.g., farmer or visitor to a live market in endemic areas) or living in an area where avian influenza is endemic. Up until now, the epidemic has been geographically focused in China.
Differentiating MERS from community-acquired respiratory tract infections is not possible from signs and symptoms.
INVESTIGATIONS
RT-PCR: positive for H7-specific viral RNA.
Respiratory syncytial virus (RSV) infection
SIGNS / SYMPTOMS
Lack of travel history to or from the Middle East (or country where there is an ongoing outbreak) in the preceding 14 days.
No close contact with a symptomatic traveller from the Middle East or a suspected or confirmed case of MERS in the preceding 14 days.
Common cause of lower respiratory tract infection in children <1 year of age and in immunocompromised patients.
Seasonal outbreak during winter.
Differentiating MERS from community-acquired respiratory tract infections is not possible from signs and symptoms.
INVESTIGATIONS
RT-PCR: positive for RSV RNA.
Community-acquired pneumonia
SIGNS / SYMPTOMS
Lack of travel history to or from the Middle East (or country where there is an ongoing outbreak) in the preceding 14 days.
No close contact with a symptomatic traveller from the Middle East or a suspected or confirmed case of MERS in the preceding 14 days.
Differentiating MERS from community-acquired respiratory tract infections is not possible from signs and symptoms.
INVESTIGATIONS
Blood or sputum culture, or multiplex RT-PCR testing: positive for causative organism (e.g., Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Moraxella catarrhalis).
Viral respiratory infections
SIGNS / SYMPTOMS
Lack of travel history to or from the Middle East (or country where there is an ongoing outbreak) in the preceding 14 days.
No close contact with a symptomatic traveller from the Middle East or a suspected or confirmed case of MERS in the preceding 14 days.
Differentiating MERS from community-acquired respiratory tract infections is not possible from signs and symptoms.
Unlikely to cause serious illness in young, healthy patients.
INVESTIGATIONS
Nasopharyngeal virus culture or RT-PCR: positive for causative organism (e.g., parainfluenza viruses, adenoviruses, rhinoviruses, enteroviruses, human metapneumovirus) or viral RNA.
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