Table 4.

Pattern of attachment of avian influenza viruses to the epithelial cells of the respiratory tract

Species	Tissues	Avian influenza viruses
		H4N5	2014 H5N8	2016 H5N8	H5N1
Mallard	Trachea	++	++	++	++
	Primary bronchus	++	++	++	++
	Secondary bronchus	++	++	++	++
	Parabronchus atria	±	±	±	±
	Air capillaries	+	±	±	+
	Air sac	++	++	++	++
Pochard	Trachea	++	++	++	+
	Primary bronchus	++	++	++	+
	Secondary bronchus	++	++	++	++
	Parabronchus atria	±	±	±	±
	Air capillaries	±	±	±	+
	Air sac	++	++	++	++
Tufted Duck	Trachea	++	+	++	++
	Primary bronchus	++	++	++	++
	Secondary bronchus	++	++	++	++
	Parabronchus atria	±	±	±	+
	Air capillaries	+	±	±	+
	Air sac	++	+	++	++
Wigeon	Trachea	++	++	++	++
	Primary bronchus	++	++	++	++
	Secondary bronchus	++	++	++	++
	Parabronchus atria	±	±	±	±
	Air capillaries	±	±	±	+
	Air sac	++	++	++	++
Chicken	Trachea	++	++	++	++
	Primary bronchus	++	++	++	+
	Secondary bronchus	++	++	++	+
	Parabronchus atria	++	+	++	++
	Air capillaries	±	–	±	+
	Air sac	++	++	++	++

Mean abundance of attachment was scored as follows: attachment to < 1% of epithelial cells (-), attachment to ≥ 1 and < 10% of epithelial cells (±), attachment to ≥ 10% and < 50% of epithelial cells (+), and attachment to ≥ 50% of epithelial cells (++).

nd not detected.