More than 160 million wild and domesticated birds have been culled in the U.S. after testing positive for avian flu in the past few years. So why is the country not rushing to vaccinate flocks to stop the spread of the outbreak?

The uptick in cases could indicate a spread of the disease or simply greater awareness of the virus, officials said.

As H5N1 spreads rapidly, wild birds remain at risk. Here’s what to know about the outbreak and how to keep your feathered visitors safe.