The U.S. Department of Agriculture last week issued a conditional license for an avian flu vaccine for use in chickens, amid an outbreak ravaging poultry flocks, contributing to the sky-high price of eggs.

The highly contagious H5N1 bird flu virus may be spreading through the air under certain conditions, according to a new study from the Czech Republic. Government veterinarians made the discovery while investigating a mysterious outbreak at a highly secured chicken farm last February.

Blue was placed under veterinary observation on Jan. 31, but his condition had not yet been diagnosed when he died earlier this month.