The bird flu virus strain that is rampant among dairy cows in the U.S. may only need one mutation for it to be able to spread among humans, according to a study published this week.

Scientists said the results of this study reinforce the need for "vigilant surveillance" of the highly pathogenic avian influenza (HPAI) H5N1, which has already spread from infected animals to humans at increasing rates.

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The study was conducted by researchers at the Scripps Research Institute and published in the journal Science. The National Institutes of Health (NIH) funded the research.

NIH said that the reason bird flu viruses have not regularly spread to people is that the human upper respiratory tract does not have the same type of cell receptors found in birds that are needed to cause an infection.

However, scientists are concerned that the viruses could evolve to recognize human-type cell receptors and gain the ability to infect people and spread between them.

Looking at a strain of H5N1 from the first human infection in the U.S. from an interaction with cattle, scientists tested multiple mutations in the gene sequence. They found one mutation that would make it easier for the virus to attach to human cell receptors.

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The authors of the study noted that the mutation testing didn't involve the creation of or experimentation with a whole, infectious virus.

These findings alone do not mean that the bird flu virus is on its way to creating another pandemic, the researchers said. There are other genetic mutations that would likely have to happen for the virus to be transmitted among people.

What the research does do is emphasize the need for continued monitoring.

To date, there have been 58 confirmed cases of bird flu in humans in the U.S., according to data from the Centers for Disease Control and Prevention.

Almost all of the human cases have been a result of interactions with affected animals — primarily dairy cattle — but there has been at least one rare case in which the human who contracted the virus had no recent animal interactions.

Nevertheless, the CDC maintains that the current public health risk is low, but added they are closely monitoring the ongoing situation.