Table 1.

Frequency of the antibody titers in dogs against the different subtypes of influenza A virus

Viral subtype	HAU 25 μl
	<20	20	40	80	160
H3N8_63	113	0	0	0	0
H3N8_97	106	2	3	0	2
H1N1pdm09	112	0	1	0	0
H1N1	108	4	0	0	1
H3N2	110	2	0	0	1

Values are expressed as hemagglutination units (HAU) at 25 μl.

Sera were considered positive when titers ≥40 were obtained.