Health officials across the world are closely monitoring the risk of avian influenza, also known as the bird flu, spilling over into a wider population of humans.
The Centers for Disease Control and Prevention says people are primarily infected when they come in contact with an infected bird.
"The spread of bird flu viruses from one infected person to a close contact is very rare, and when it has happened, it has not led to continued spread among people," the CDC says.
Health officials have expressed concern as the virus continues to spread among different types of animals. The fear is that the virus will adapt and spread more easily among humans.
Why is bird flu causing new concern?
In recent months avian flu has decimated bird populations and has now spread among several different mammal species.
The World Health Organization said in a report last week that the threat of people catching avian influenza from birds is elevated due to the spread among birds. However, it notes that the overall pandemic risk has "not significantly changed in comparison to previous years."
Despite the current pandemic threat remaining similar to previous years, pharmaceutical companies are preparing a human vaccine to protect against the bird flu.
GSK said it was awarded contracts with the U.S., Canada, the European Union and the World Health Organization to supply a vaccine should a pandemic be declared.
Moderna said it expects to start clinical studies for a pandemic bird influenza vaccine this year.
Grizzly bears in Montana tested positive for avian influenza
The three bears were euthanized due to their sickness and poor condition.
