In August 2005, Hurricane Katrina, the third-strongest hurricane in the history of the United States, made landfall, decimating New Orleans, a city with levees built to withstand a Category 3 storm. Katrina, at its height, was a Category 5.

About 1,836 people, more than half of them senior citizens, died in the tragedy. The Federal Emergency Management Agency (FEMA) called it "the single most catastrophic natural disaster in U.S. history."

Those who did not evacuate — about half of whom had pets — took to their rooftops to escape the rising waters. Many of them sat with their dogs and cats, waiting for help to arrive. Help did come, but not for the animals. The rescuers mostly refused to take animals on board, making it clear that the pets must be left behind.

One particular story gripped the nation and personified the problem: A boy who boarded a bus to be evacuated to Houston had his dog taken away by a police officer. The boy called out for the animal — "Snowball! Snowball!" — and then vomited from the stress and heartbreak.

Dogs and cats were left on rooftops to starve or die of dehydration. Some dogs entered the water, trying to swim to dry land. In some instances, the owners refused to leave their companion animals and perished alongside them. In total, 250,000 pets were left behind and 150,000 died during the hurricane or in its aftermath, reports BuzzFeed.

These tragedies played out on televisions, newspapers and websites, prompting outrage that there was no plan in place to help pets and companion animals. Countless pets died or were sent to shelters, many never to be reunited with their families.

Animal rescuers flocked to the area and did their best to find the animals left behind, breaking into homes if necessary, and searching the streets for animals that had been abandoned.

A spray-painted note makes mention of rescued cats in a New Orleans home following Hurricane Katrina. Robyn Beck/Getty Images

A new law to protect animals in natural disasters

It was clear that the government had underestimated the strength of the bond between people and their animals. The public outrage that followed the hurricane led to some lasting change for pets in disaster situations. Less than a year after Katrina, the Pet Evacuation Transportation Standards (PETS) Act of 2006 was created in a bipartisan effort.

The law demands that state and local governments factor pets into emergency evacuation plans, and authorize the use of funds for rescue workers to "procure, construct, or renovate emergency shelter facilities and materials that will temporarily accommodate people with pets and service animals."

"The scene from New Orleans of a 9-year-old little boy crying because he was not allowed to take his little white dog Snowball was too much to bear," explained then-U.S. Rep. Tom Lantos of California, who was the primary bill proposer at the time. "Personally, I know I wouldn't have been able to leave my little white dog Masko to a fate of almost certain death. As I watched the images of the heartbreaking choices the Gulf residents had to make, I was moved to find a way to prevent this from ever happening again."

The law doesn't just help animals. It helps people. The Centers for Disease Control and Prevention acknowledges that households with animals are much less likely to evacuate in a disaster if there are no shelters available to accommodate their pets.

"It is simply not acceptable to the majority of Americans to leave behind pets and companion animals," says Dr. Stephanie Ostrowski, D.V.M., M.P.V.M., who is also board-certified with the American College of Veterinary Preventive Medicine. "Witnessing the abandonment of any household member to his fate is profoundly distressing and increases anxiety about an individual's own safety and security. Consequently, CDC's role in these efforts was, at its core, an important and wide-ranging public health mission."

The bond between companion animals and people has been evident for thousands of years. It's common to see humans searching through the rubble after earthquakes and tornadoes for signs of their pets. Katrina, and the media surrounding the disaster, was a wake-up call, inspiring the United States to take animal lives into consideration during natural disasters.

The law takes a step forward, but it doesn't cover all animals. FEMA and the Humane Society of the United States suggest that those with farm animals prepare a plan in advance to ensure the safety of all domesticated animals.