The poop, or guano, of infected birds is teeming with viruses. Out of all known influenza subtypes, all but two have been found in birds. The other two subtypes have only been found in bats.

VANEK SMITH: Now, to raise awareness, researchers have put a dollar value on the birds' poop, also known as guano. DANIEL PLAZAS-JIMENEZ: They call the guano the white gold. SHAPIRO: White gold.