For influenza viruses, imperfection is a strength. They constantly mutate, producing new strains that challenge immune systems primed to fight earlier varieties. That’s what makes flu a life-long threat to humans and the animal species — mainly birds — that are vulnerable to it.

Medical experts advise that people should get a vaccine for the bird flu when it becomes commercially available. One doctor said the most at-risk patients should be first.

A person from Louisiana was reported dead after getting infected with bird flu on Monday. According to the reports, the 65-year-old man was hospitalized with symptoms of bird flu or H5N1 and ultimately passed away from the infection.