Table 1.

Comparison of the immunopathology in COVID-19, SARS, MERS and influenza infection. + = has been reported; NS = not stated.

	Influenza infection	COVID-19	SARS	MERS	[Ref.]
Hyperinflammation
Hypercytokinemia associated with poor prognosis	+	+	+	+	[34,78,80,119,120]
Increased CRP levels associated with poor prognosis	+	+	+	+	[27,29,30,41,121,122]
Hyperferritinemia associated with poor prognosis	+	+	+	NS	[28,31,123]
Immunosuppression
Lymphopenia associated with the severe disease	+	+	+	NS1	[40,41]
Reduction of NK cell counts in the blood and/or NK cell dysfunction associated with the severe disease	+	+	+	NS	[41,124]
Reduction of both CD4 and CD8 T cell counts in the blood associated with severe disease	+	+	+	NS	[41,52]

¹Lymphopenia is commonly observed in patients with MERS, however, its association with the disease severity has not been studied.