Concerns about bird flu are growing among health officials weeks after the first person in the U.S. died from the virus, and as cases of bird flu grow among animals and humans. Minnesota has no cases of bird flu infection in humans,

H5N1 avian influenza continues to spread amid commercial and backyard poultry, and additional cases have been reported in domestic cats

How deadly is the bird flu? The US has reported its first death from avian influenza, H5N1. Here's what to know about bird flu mortality rate and who is at risk.

H5N1 first human death was reported in USA. Since then, health authorities have been monitoring and cases and shave sounded alarm regarding its mutation rate.

In a press release issued on Jan 15., the San Antonio-based research team said mutation was more possible in humans.

On Thursday, the U.S. Centers for Disease Control and Prevention confirmed another case of avian influenza A(H5N1), or bird flu, in California, bringing the nationwide total of cases to 67.

"The Chinese poultry lineage may have experienced more vaccine-driven selection compared to other lineages," the researchers wrote.

H5N1 vaccines have been previously licensed, and millions are in the national stockpile. But even with the news of the country’s first human death due to bird flu, vaccination isn’t yet recommended.