Researchers from the SUNY Downstate Medical Center have identified certain areas in western United States at high risk of the plague, mapping out locations where the Yersinia pestis bacteria has a high probability of occurring.

Publishing their findings in the journal PeerJ, the researchers were able to predict the would-be affected areas based on reported occurrences of the plague in both wild and domestic animals. Typically, the disease is caused by a bacteria found in rodents and their fleas.

According to Michael Walsh, Ph.D., M.P.H., an assistant professor from the Epidemiology and Biostatistics Department of SUNY Downstate's School of Public Health, the mapped areas showed the greatest potential for human exposure to the disease, which can be deadly when transmitted to humans.

"The findings can be used ... to target specific areas for enhanced plague surveillance ... as well as by other research teams to direct the sampling of local wildlife populations," he said.

While the researchers acknowledge that animal-to-human transmissions are not very common today, they reiterate that plague risk remains significant in certain portions of western U.S. Not to mention that this risk also extends to threatened species part of the epizootic cycle.

To create their model, the researchers used ecologic niche data of the plague identified in wild and domestic animals from 2000 to 2015. An algorithm was developed to predict the niche based on the presence of the deer mouse Peromyscus maniculatus (an important carrier species), land cover, altitude and climate.

Using their predictive model, the researchers identified areas at high risk of the plague as northeastern and southwestern California, north-central New Mexico and central Colorado.

According to the U.S. Centers for Disease Control and Prevention, the plague was first spotted in the country in 1900, spread by rat-infested steamships sailing from affected areas. The first to fall were the port cities, while the last epidemic of the plague was reported in 1924 to 1925 in Los Angeles. However, the plague spread to rural rodents, bringing the disease to many areas in western U.S. Back then however, most human plague cases were reported in far western Nevada, southern Oregon, California, southern Colorado, northern Arizona and northern New Mexico.

The CDC records an average of seven human cases of the plague every year. The disease affects individuals of all ages but 50 percent of cases occur in people between the ages of 12 and 45.

Photo: Seney Natural History Association | Flickr