Table 3. Microscopic lesions documented in harbor (Phoca vitulina) and gray (Halichoerus grypus) seals infected by HPAI A(H5N1) during the 2022 outbreak in the St. Lawrence Estuary, Quebec, Canada.

Microscopic lesions	% Seals affected (no. with lesions/no. examined)
Brain
Meningoencephalitis	100 (15/15)
Predominantly neutrophilic	80 (12/15)
Predominantly lymphoplasmacytic	20 (3/15)
Lung
Pulmonary inflammatory changes	73 (11/15)
Acute multifocal fibrinosuppurative alveolitis	60 (9/15)
Acute interstitial pneumonia	53 (8/15)
Acute alveolar damage	40 (6/15)
Alveolar emphysema	27 (4/15)
Adrenal gland
Adrenocortical necrosis	60 (6/10)
Thymus
Acute multifocal necrotizing thymitis	50 (2/4)
Lymph nodes
Reactional lymph nodes	43 (6/14)
Acute multifocal necrotizing lymphadenitis	36 (5/14)
Kidney
Multifocal membranous glomerulonephritis	40 (6/15)
Liver
Necrotizing hepatitis	29 (4/14)
Spleen
Necrotizing splenitis	21 (3/14)
Muscle
Neutrophilic infiltration of the perimysium	9 (1/11)
Heart
Multifocal myocarditis	7 (1/14)