As the US struggles to bring its coronavirus outbreak under control, another virus is wreaking havoc among the country's rabbit population.

Across seven states in the southwest, thousands of wild and domestic rabbits are dying from a rare outbreak of a highly contagious disease known as rabbit hemorrhagic disease virus (RHDV2).

"We refer to it as 'bunny ebola'," Amanda Jones, a veterinarian from Killeen, Texas, told The Cut.

While the rabbit virus is "not related in any way, shape, or form" to Ebola – a virus that causes severe bleeding, organ failure, and death in humans and primates – Jones said RHDV2 ravages rabbit bodies in a similar manner.

The virus causes lesions in rabbits' organs and tissues, which leads to internal bleeding and death. Often the only outward sign that the animals are infected comes after their death: After suddenly dropping dead, their noses leak bloody discharge.

Since April, the US Department of Agriculture (USDA) has confirmed RHDV2 cases in Arizona, California, Colorado, Nevada, New Mexico, Utah, and Texas. Parts of western Mexico have also been hit with the virus.

A virus that's 'moved like mad'

This outbreak is the fourth time RHDV2 has been reported in the US. (Variants of the virus have spread across almost every continent since scientists reported the first case in China 35 years ago.)

But it's the first time the virus has spread beyond domesticated animals to hit rabbits, pikas, and hares native to North America. Cottontails, snowshoe hares, and jackrabbits have all gotten sick.

"The fact that this is in multiple counties and rabbitries, that's why this is so concerning," Eric Stewart, executive director of the American Rabbit Breeders Association, told VIN News.

"And then to hear it's burning through the wild rabbit populations, that, of course, furthers our concerns that much more."

In 2018, the virus popped up among pet rabbits in Ohio, then a separate outbreak happened in Washington state. In late February, more than a dozen rabbits died at the Centre for Avian and Exotic Medicine in Manhattan, succumbing to the virus in minutes amid violent seizures.

This southwestern outbreak, which appeared in Arizona and New Mexico a month later, is unrelated to those three.

"We still have no idea where it originated," Ralph Zimmerman, New Mexico state veterinarian, told the Cut. "It's snowballed and moved like mad."

Nearly 500 animals in New Mexico were infected between March and June.

"We had one guy with 200 rabbits, and he lost them all between a Friday afternoon and Sunday evening," Zimmerman added. "It just went through and killed everything."

New Mexican officials instituted a depopulation policy, The Cut reported. If one rabbit in a home caught the disease, the state requires the remaining rabbits in the nest be euthanised. That led another 600 animals to be killed in the attempt to stop the virus' spread.

By April, researchers had reported cases in rabbit populations in Colorado, Texas, and Nevada as well. Dozens more then popped in California and Utah.

"I'm going to be really honest with you. I think there are more cases than have been reported," Jones told The Cut.

A highly contagious, hard-to-kill virus

'Bunny ebola' kills with startling efficiency.

Once an animal is infected, the virus incubates in as few as three days. Some bunnies start to lose their appetites and energy, though others show no outward symptoms before dropping dead.

Ultimately, the rabbits' organs – livers and spleens – fail and their blood stops clotting properly. In the current outbreak, officials have reported a death rate of about 90 percent.

The bunnies that do survive become severe hazards to others, since they continue shedding virus for nearly two months.

RHDV2 spreads easily through blood, urine, and faeces.

While the virus can't infect humans or other types of animals, it can stick to hair, shoes, and clothing to move between bunny hosts. If a rabbit touches a surface contaminated by viral particles, it could get sick. Insects that roam between rabbits can spread particles, too.

The virus is also hard to kill: It can live for more than three months at room temperature. It survives temperatures of 122 degrees F (50 C) for at least an hour and can't be killed by freezing, according to the House Rabbit Society.

What's more, the virus has no cure, and obtaining a vaccine in the US is a time-consuming process.

Getting a vaccine in the US takes weeks

Since the virus originated overseas, there's no licensed vaccine available in the US yet.

Instead, vets like Zimmerman and Jones have to request permission from the USDA to import vaccines from Spain and France. That approval process takes at least a month.

Jones told The Cut she put in her order mid-April and received it June 9; one of Zimmerman's orders took five weeks to arrive.

The USDA is working to domestically produce a RHDV2 vaccine, but the process will likely take a year or more, according to the House Rabbit Society.

"This isn't just going to go away," Jones said. "This is a new problem that's here to stay."

This article was originally published by Business Insider.

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