bacterium

Animals live in much greater concentrations in rural areas, where they are in closer proximity to other creatures and habitats, making it easier for the bacterium to thrive, Swartzberg said.

The disease is caused by the bacterium Yersinia pestis and is most commonly spread to humans by bites from infected fleas, according to El Dorado County health officials.

Listeria is a microscopic bacterium often found in deli meats, hot dogs, and soft cheeses.

The product is made from small, purified doses of botulinum toxin, produced by the bacterium Clostridium botulinum.

Pneumonic plague is a severe lung infection caused by the Yersinia pestis bacterium.