Rabies is a deadly virus that infects the central nervous system and kills more than 59,000 people each year.

Now, a Centers for Disease Control and Prevention-led study has found a new variant in central New Mexico.

The years 2015 and 2019 each saw a person in Lincoln County, New Mexico, bitten by a gray fox (Urocyon cinereoargenteus) carrying the same previously unknown strain of rabies.

The strain likely originated in tree-dwelling bats.

Until they find its reservoir species, experts cannot say if the variant has shifted hosts, which is rare.

Since 2015, bats have become the most common rabies reservoir in the continental U.S. and host at least 18 distinct variants, some of which have shifted to land mammals.

Migratory tree bats usually travel long distances, which could bring the variant to other states or countries.