Coronaviruses are a group of viruses that infect animals and humans, and cause respiratory and intestinal distress. Known coronaviruses generally led to mild illnesses in people until the emergence of severe acute respiratory syndrome (SARS) in 2002 and 2003, and Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012. It's thought that these viruses originated in bats; SARS likely spread from bats to civets to people, while MERS spread from bats to dromedary camels to people. While the origins of the pandemic virus SARS-CoV-2 is still debated, it has confirmed that coronaviruses can be extremely dangerous and disruptive.
Sarbecoviruses are one type of coronavirus that can be found in bats, and some, like RaTG13 are close relatives of SARS-CoV-2. A new study has shown that some people in rural Myanmar (also known as Burma) in Southeast Asia carry antibodies to sarbecoviruses, which indicates they have been infected with these viruses at some point.
The study, which was reported in the International Journal of Infectious Diseases, has determined that when people living in these areas performed tasks that put them in close proximity to bats, such as hunting, logging, or harvesting bat guano, they were significantly more likely to be exposed to sarbecoviruses.
"This study provides new evidence that bat-borne coronaviruses can and do spill over to people, underscoring the importance of surveillance in high-risk rural areas, where humans and wildlife closely interact," said lead study author and epidemiologist Tierra Smiley Evans of the One Health Institute at University of California, Davis.
In this work, the researchers and colleagues in Myanmar screened about 700 people for sarbecoviruses. The samples were taken from July 2017 to February 2020, and before SARS-CoV-2 began to cause infections in the area.
No active sarbecovirus infections were identified, but twelve percent of study volunteers were found to carry antibodies that showed they had been exposed to a sarbecovirus at some point. It seems that only individuals from rural areas were at risk, and most of the people who had been infected worked in industries such as mining, hunting, and logging. The study authors suggested that when people are working in biodiverse places, or near the wildlife-urban interface, the risk of exposure to a virus that is zoonotic, or can pass from an animal to a human, is increased.
The researchers did not look for sarbecoviruses in animals, and instead focused on people who had sought care for fever, or had worked in logging in rural and urban areas. There are networks of small, temporary villages in Myanmar where people live and work, and where they are in close proximity to many bats. By obtaining samples from these individuals, the investigators can get some idea of what might be in the forest without going there.
The work has also shown that zoonotic spillover is an ongoing event. The scientists stressed the importance of surveillance that can detect emerging viruses in Southeast Asia, which is known to be an area with high levels of mammalian diversity, and the potential for zoonosis is high.
Sources: University of California Davis, International Journal of Infectious Diseases
