[2] Symptoms of A/H7N9 influenza vary according to both the strain of virus underlying the infection and on the species of bird or mammal affected.

[5] Chickens infected with LPAI A/H7N9 virus display mild symptoms or are asymptomatic, whereas HPAI A/H7N9 causes serious breathing difficulties, a significant drop in egg production, and sudden death.

[6] In mammals, including humans, A/H7N9 influenza (whether LPAI or HPAI) is rare; it can usually be traced to close contact with infected poultry or contaminated material such as feces.

Its ability to cross the species barrier renders it a potential pandemic threat, especially if it should acquire genetic material from a human-adapted strain.

[17] The segmentation of its genome facilitates genetic recombination by reassortment in hosts infected with two different strains of influenza viruses at the same time.

Symptoms of influenza in birds may include swollen head, watery eyes, unresponsiveness, lack of coordination, respiratory distress such as sneezing or gurgling.

[30] All subtypes of avian Influenza A have potential to cross the species barrier into humans, with H5N1 and H7N9 considered the biggest threats.

[13][35] In order to contain the HPAI outbreak, the Chinese authorities in 2017 initiated a large scale vaccination campaign against avian influenza in poultry.

It has demonstrated antigenic drift to evade vaccines, and remains a potential threat to the poultry industry and public health.

This new strain resulted from the recombination of genes between several parent viruses noted in poultry and wild birds in Asia.

If the virus were to acquire the ability to transmit easily between humans (either through mutation or genetic reassortment) there is potential for a severe epidemic or pandemic.

[41] The continuing evolution and antigenic drift of the A/H7N9 virus makes further development difficult as any significant outbreak could involve a completely new strain.