As the COVID-19 pandemic threat seemingly fades into the annals of history, scientists are attempting to identify which pathogen will pose the next large-scale threat to humanity.

Instead of a resurgence of COVID or an avian flu, it just may be the little-known yet formidable Langya virus, which shares similarities with COVID, according to a new article published this month in the journal Nature Communications.

As with COVID initially, the virus causes fever and severe respiratory symptoms, and can lead to fatal pneumonia. Also like COVID, it was first identified among humans in China—last year, when it infected 35 farmers and other residents, likely due to contact with shews.

It wasn’t the first time a Henipavirus—the family Langya belongs to—has jumped to people, and it won’t be the last, researchers warn.

Dr. Ariel Isaacs—a researcher at the School of Chemistry and Molecular Biosciences at the University of Queensland in Australia—said humanity is at an “important juncture” with the genus of viruses and can “expect more spill-over events from animals to people.”

“It’s important we understand the inner workings of these emerging viruses,” he said in a news release about the research.

Here’s what we know about the relatively new (to humans) virus with the potential to cause a global health emergency—and with eerie similarities to the latest human coronavirus.

What are Henipaviruses?

Henipaviruses are the most lethal of paramyxoviruses, killing around 70% of those who contract them. The first two Henipaviruses identified in humans were the Nipah virus, first seen in pigs in Malaysia and Singapore in the late 1980s, and the Hendra virus, first noted in race horses and humans in Australia in 1994.

Pigs, fruit bats, cats, dogs, horses, and humans are natural carriers of Henipaviruses, according to the World Organisation for Animal Health.

So far, cases of Hendra virus have been limited to Australia. Nipah, however, has posed a greater problem. Additional outbreaks in Bangladesh and India in the early 2000s—caused by a different strain of the virus than the one seen initially—were thought to have occurred due to consumption of fruits or fruit products like raw date palm juice “contaminated with urine or saliva from infected fruit bats,” according to the World Health Organization. Outbreaks occur almost annually in Bangladesh, according to the new paper’s authors.

More concerningly, transmission of Nipah among humans has been reported, in family members and caregivers of those sickened, the authors wrote. (Avian flu has so far failed to become a global health problem because of its inability to effectively transmit between humans.)

Both Hendra and Nipah viruses can present with respiratory illness and severe flu-like symptoms, and may progress to encephalitis—inflammation of the brain—along with other neurologic symptoms and death.

What’s more, new Henipaviruses are routinely being discovered in animals, including the Cedar virus in fruit bats in Australia, the Ghana virus in bats in Africa, the Gamak & Daeryong viruses in shrews in Korea, and the Mòjiāng virus in rats in China. It’s suspected that the Ghana virus can spill over to humans, as is the case with Nipah, Hendra, and Langya viruses, according to the authors. The Mòjiāng virus has also reportedly infected people.

The ability of Henipaviruses to “infect a wide range of hosts and to produce a disease that causes significant mortality in humans has made them a public health concern,” according to a brief published by the WHO in 2016.

How does Langya virus compare to other Henipaviruses?

Langya is most closely related to the Mòjiāng virus, which presents with symptoms startlingly similar to those of the initial COVID-19, according to the authors. Like COVID initially did, Langya and Mòjiāng are known to cause severe pneumonia. And Mòjiāng tends to cause ground-glass opacities on lung X-ray in those infected, as well as the often-fatal severe acute respiratory distress syndrome (ARDS)—two more similarities with the initial COVID-19, according to a 2020 article in Frontiers in Public Health.

The Mòjiāng virus was discovered in 2012, when it reportedly sickened six miners and killed three who had contact with bats in the Tongguan mineshaft in Mòjiāng, China. A coronavirus closely related to COVID-19 was found in the same mineshaft, the authors of the 2020 article noted, raising more questions than answers, given the similar presentation of the two viruses.

Is there a vaccine or treatment for Langya virus or other Henipaviruses?

Not at the moment. The group of viruses is on WHO’s list of diseases for which it’s prioritizing research in vaccines and therapeutics. That’s partially because of the high case fatality rate of the viruses, as well as the fact that fruit bats that harbor them migrate globally, facilitating wide spread.

A vaccine against Hendra virus is currently available for animals, and trials of a similar vaccine are underway in humans, according to the authors. A vaccine for Hendra virus is not likely to work on Langya, the authors noted. It’s also unlikely to work against Mòjiāng, which is more similar to Langya than Hendra, they added.

Isaacs and his team plan to continue their work on developing broad-spectrum vaccines that can ward off Henipaviruses in humans.

“These are viruses that can cause severe disease and have the potential to get out of control if we’re not properly prepared,” Dr. Daniel Watterson, another researcher at the School of Chemistry and Molecular Biosciences at the University of Queensland and an author on the paper, said in the news release.

“We saw with COVID-19 how unprepared the world was for a widespread viral outbreak, and we want to be better equipped for the next outbreak.”