We still don't have a final answer whether COVID-19 originated from a wild animal in a market or a caged one in a laboratory. You'd think we'd nail that down, since the virus killed at least 7 million people.
We do know one thing: the virus came from a bat.
Well, we're not 100% certain about the bat, but all evidence points that way: the virus is nearly genetically identical to one found in horseshoe bats in Yunnan Province, China. And bats have a long history of hosting viruses that jump to humans, like SARS and MERS. How COVID-19 passed to humans is still a mystery, but we're pretty certain the virus started in a bat.
So it makes sense we continue to study these animals, particularly those in Yunnan, China. We want to prevent the next global pandemic.
If you're thinking of joining a team of scientists on the next plane to China to stop the next COVID, there's something you should know: the process of testing bats for viruses usually involves analyzing their feces. This allows scientists to test bats without capturing or harming them. Scientists can also sample a lot of bats at once, since they roost together in large colonies and, well, you get the picture.
But a recent study of the bat infectome (all the viral and bacterial microorganisms living in a bat) took a much different approach. The results were published this month in the PLOS Pathogens Journal by the Yunnan Institute of Endemic Disease Control and Prevention. Their process involved two major innovations. First, they focused on the bat's kidneys instead of the feces. The kidneys can contain pathogens transmissible through blood or urine that fecal studies might miss. Second, the study was the first to search for germs using meta-transcriptomic sequencing. In other words, they extracted the bat's RNA.
The study involved sampling kidney tissues from 142 bats across five locations in Yunnan province, the infamous hotspot for bat-borne viral pathogens. Because of their focus on RNA, the amount of data they gathered was astounding. For every group of bat kidney samples, they extracted 56 million pieces of genetic material. By the end of the study they had 1.13 billion "reads", or pieces of RNA. Through this process, the scientists were able to identify any viral, bacterial, fungal, or protozoan RNA.
And what they found was alarming.
Ideally, of course, you'd find no viruses in wild bats, especially any that could spread to humans. You sure don' t want to uncover any new viruses.
The Yunnan study found twenty-two different viruses. Out of those, twenty were completely novel discoveries, never before categorized by the International Committee on Taxonomy of Viruses (ICTV).
The good news is, none of these were similar to COVID-19. The family Coronaviridae, to which SARS-CoV-2 (the virus causing COVID-19) belongs, is not one of the viral families found in the samples.
But that's where the good news ends.
Because they did find two novel henipaviruses. They may not be as well-known as SARS-CoV02, but they have two horrible traits in common. First, both henipaviruses are zoonotic -- a much scarier term than it might sound. It means they're capable of spreading from animals to humans, which is how we got Ebola and SARS-CoV-2.
Second, the two henipaviruses found in the wild bats were from the same genus as the Nipah and Hendra viruses, making them potentially lethal.
If someone is infected with a henipavirus, it can cause acute brain inflammation, seizures, and even a coma. If it gets in a patients lungs, they will have trouble breathing, and they might get pneumonia or acute respiratory distress syndrome (ARDS). As the infection spreads, it can damage multiple organs--lungs, brain, heart, kidneys--leading to organ shutdown. Ultimately, the Nipah virus has a terrifying fatality rate of up to 75% depending on the circumstances (how quickly the health system responds, or the health of the patient initially). Similarly, the Hendra virus kills 60% of those infected. And even if you survive, the virus lives on and can cause a relapse months later, bringing on encephalitis or permanent neurological problems.
So they found these viruses in the wild. What now? How do they intend to prevent spillover - the nice way of saying infecting human beings?
The plans are to continue their research and surveillance of the bats. They investigate other organs in the bats to test how the virus might be spreading. They assess transmission risks, and try to understand how to best prevent the virus from contaminating food sources and advise public health officials. And they push for more studies to keep an eye on the viruses.
The plans are not so comforting. They don't include "getting rid of all the bats in China", for example. Because, the thing about lethal viruses found in the kidneys, they can spread in a very obvious way: they can be shed through urine.
The scariest thing about the henipaviruses found in the study? There are no widely available vaccines or cures. If an infected human doesn't get immediate care, the prognosis is not good.
The world should be grateful science was able to uncover these lethal viruses in wild bats. But it is concerning that the bats collected in the study were all found in Yunnan Province . . . near populated villages and fruit orchards.