Table:

Subtypes of novel influenza A viruses and clinical syndromes in human infections

	LPAI viruses	HPAI viruses	Variant viruses*
Conjunctivitis	H7N2, H7N3, H7N7, H10N7	H7N3, H7N7	H1N1v, H3N2v
Upper respiratory tract illness	H6N1, H7N2, H7N3, H7N9, H9N2, H10N7	H5N1, H5N6, H7N7	H1N1v, H1N2v, H3N2v
Lower respiratory tract disease, pneumonia	H7N2, H7N9, H9N2, H10N8	H5N1, H5N6, H7N7, H7N9	H1N1v, H3N2v
Respiratory failure, acute respiratory distress syndrome	H7N9, H10N8	H5N1, H5N6, H7N7, H7N9	H1N1v, H3N2v
Multiorgan failure	H7N9, H10N8	H5N1, H5N6, H7N7, H7N9	··
Encephalopathy or encephalitis	H7N9	H5N1	··
Fatal outcomes†	H7N9, H9N2, H10N8	H5N1, H5N6, H7N7, H7N9	H1N1v, H3N2v

A novel influenza A virus is an influenza A virus that has infected humans and is antigenically and genetically distinct from seasonal influenza A viruses circulating among humans. We have included virologically confirmed infections only; laboratory accidents or transmissions from experimentally infected animals were excluded. Data are from published case reports and case series, WHO Disease Outbreak News, and WHO Monthly Risk Assessment Summaries (appendix). LPAI=low pathogenicity avian influenza. HPAI=highly pathogenic avian influenza.

^*Variant viruses of swine origin.

^†High mortality in reported cases: about 40% for LPAI H7N9, about 50% for HPAI H5N1, and about 70% for HPAI H5N6.