Table 1.

Tissue tropism of influenza virus infection of human bronchus and lung as assessed by immunohistology

	Bronchus	Lung
Sh1/H7N9	++	++
Sh2/H7N9	++	++
NL/219/H7N7	+	+
H5N1	+/−	+
H1N1/pdm	+	++
Duck/H7N9	Sparse	−

Sections were stained with a monoclonal antibody to influenza nucleoprotein and scored in a semiquantitative manner: ++=more than 20% of epithelial cells have positive antigen. +=5–20% of epithelial cells have positive antigen. +/−=less than 5% of epithelial cells have positive antigen. Sparse=only 1–3 positive cells identified per section. −=no positive cells identified.