This summer 2018 photo provided by the Marine Mammal Center shows California sea lion Yakshack at the Marine Mammal Center, a rescue center in Sausalito, Calif. The center says California sea lions are coming down with a potentially fatal bacterial infection in near-record numbers. (Bill Hunnewell/Marine Mammal Center via AP)

A rescue center says California sea lions are coming down with a potentially fatal bacterial infection in near-record numbers.

The Marine Mammal Center in Sausalito says more than 220 sea lions rescued this year have been diagnosed with leptospirosis.

It's the second-largest outbreak recorded by the rescue center.

The center says outbreaks aren't uncommon but the last major one was in 2011. It involved nearly 200 sea lions.

The affects the kidneys and can be lethal if untreated. The Marine Mammal Center says the strain affecting the sea lions has also been seen in pigs, skunks and foxes. It's transmitted through infected urine, either directly or in contaminated water or soil.

It's unclear how the contracted the infection.

  • This summer 2018 photo provided by the Marine Mammal Center shows California sea lions Bogo, from left, Brielle and Biggie at Rodeo Beach near Sausalito, Calif. The rescue center says California sea lions are coming down with a potentially fatal bacterial infection in near-record numbers. (Bill Hunnewell/Marine Mammal Center via AP)

  • This summer 2018 photo provided by the Marine Mammal Center shows a California sea lion prior to its rescue at a Monterey County beach along central California coast. The rescue center says California sea lions are coming down with a potentially fatal bacterial infection in near-record numbers. (Marine Mammal Center via AP)