Two cranes cared for by the Metro Richmond Zoo are dead after they became sick with bird flu. Bird flu, otherwise known as avian influenza, is a disease that spreads naturally among wild water birds worldwide,

The two cranes passed away from the disease. The affected birds did not live in an aviary that shares a common space with the public, the zoo said.

The zoo says the birds did not live in any of its aviaries, where the public shares a common space with birds.