A decision made about one dog may have led to a deadly Canine Distemper outbreak at a local animal shelter.

More than a dozen dogs at Stray Rescue of St. Louis have died from the virus and at least seven others are sick.

Now, Stray Rescue's founder believes an extremely pregnant dog that was brought to the shelter two months ago may be to blame for the outbreak.

“We don't typically vaccinate a mother in labor and she wasn't showing any symptoms. So, we wouldn't have thought to even worry about that,” said Randy Grim.

During a conference call Tuesday with distemper experts at the University of Wisconsin, Grim learned the dog could've been vaccinated when it was brought in, just like every other animal the shelter accepts.

“The problem is there was so much cross-contamination,” Grim said.

With no signs of illness, Grim said staff members who worked with the dog may have then come in contact with other animals, helping to spread the virus.

Veterinarians say it's not uncommon for a sick dog to show no symptoms.

“Distemper can show up as many different things,” said Dr. Mark Wright, Director of Shelter Medicine at the Humane Society of Missouri. “It doesn't always show up right away after exposure. It can be a several week delay, so it can really cause havoc for a shelter.”

For those reasons, the Humane Society keeps strays isolated until it's clear the animal isn't sick.

That's one of a few extra precautions Grim and his team will take moving forward.

“We're building a new intake room and we're going to just up our game on protocols. The folks in intake need to stay in intake for two weeks, not a week,” said Grim.

The long days of testing and treating sick dogs have been taxing on Stray Rescue's staff. But donations and community support are helping lift their morale.

“The community response has been overwhelming. It's been amazing and it hasn't stopped. As soon as our doors open people just pile in with more and more supplies,” said Grim.

Anyone wanting to help can donate to the shelter. They are looking for the following items.

Stray Rescue donations