Medical experts are concerned about the growing possibility of human-to-human transmission of bird flu, as the disease continues to ravage cattle and poultry populations.

A new study from the Scripps Research Institute found that the disease is only one mutation away from latching on to human cells, making it easier to spread between people.

“We now have multiple cases of bird flu involving children in the U.S. and in Canada, individuals for whom the source of their infection is not clear,” said Dr. Leana Wen, former Baltimore health commissioner and professor of public health at George Washington University, during an appearance on WYPR’s Midday show. “Initially, it was only poultry workers and dairy workers who were getting infected with bird flu through occupational exposure. Now we have individuals who we have no idea where they got this from, and so that leaves the question - is there human-to-human transmission that may be underway?”

Only 54 people have been officially diagnosed with the disease, according to the Centers for Disease Control and Prevention.

However, only certain states are testing for the disease.

Wen said that there is concern that health officials are not doing enough to prepare for potential crises like bird flu.

“There is an unwillingness to look at something and think about and invest in prevention before it becomes a crisis,” Wen said. “I think this is what's happening with bird flu as well. We have not been investing nearly enough in testing.”

There is a vaccine for bird flu. The United Kingdom bought five million doses of the inoculation last week in preparation for a possible pandemic.

Symptoms of bird flu include fever, sore throat and coughing.