A spate of dog deaths on the mainland and Canada is raising concerns about a serious bacterial infection called leptospirosis.

Part of the problem with leptospirosis is it often goes unrecognized or undiagnosed until it's too late.

"Hawaii is the number one state for leptospirosis," says Dr. Eric Ako of The Pet Doctor in Hawaii Kai.

Dr. Ako is quite familiar with the bacterial disease. He says it's not unusual for dogs to return infected after a hiking excursion.

Leptospirosis is spread through infected animal urine. You'll often see warning signs along Hawaii streams, where rats or pigs might relieve themselves.

The vaccine that vet offices carry doesn't cover every bacterial strain. That's why pet owners and people in general need to be alert.

"Be aware that any time you may come in contact with rat urine or your pet, and you shortly start feeling feverish or ill, you should think about it and report it to your physician," says Dr. Ako

There's no generally-approved human leptospirosis vaccine, but Dr. Ako says people typically do well with antibiotics, once it becomes clear what they have.

"It is a treatable disease," says Dr. Ako. "In fact, most cases respond quite nicely to the penicillin family, but you have to think about it and the physician needs to think about it."

On the mainland, animals such as raccoons, skunks and squirrels carry a separate strain not found here and they pose an additional leptospirosis problem because they're also plentiful in urban environments.