I also found this online as a possibility, but a possibility we will hope is unfounded as there's no cure.
Respiratory Disease
Peacocks can get respiratory diseases such as Newcastle disease or fowl pox that spread rapidly and can’t be treated once the disease has made itself known. Other respiratory illnesses show up as swollen eyes or sinuses. The effects of these diseases can be helped with antibiotics, but they may never go away completely. Keeping your peafowl's housing sanitary and keeping them from sick birds are defenses against respiratory illness.
Respiratory Disease
Peacocks can get respiratory diseases such as Newcastle disease or fowl pox that spread rapidly and can’t be treated once the disease has made itself known. Other respiratory illnesses show up as swollen eyes or sinuses. The effects of these diseases can be helped with antibiotics, but they may never go away completely. Keeping your peafowl's housing sanitary and keeping them from sick birds are defenses against respiratory illness.