Researchers from Brazil's state-run Fiocruz Institute shine a light on a bat they captured in the Atlantic Forest during a nighttime outing in Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. The outing was part of a project to collect and study viruses present in wild animals — including bats, which many scientists believe were linked to the outbreak of COVID-19. (AP Photo/Silvia Izquierdo)

A researcher for Brazil's state-run Fiocruz Institute holds a bat captured in the Atlantic Forest, at Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. Researchers at the institute collect and study viruses present in wild animals — including bats, which many scientists believe were linked to the outbreak of COVID-19. (AP Photo/Silvia Izquierdo)

A researcher for Brazil's state-run Fiocruz Institute sets up a net for ensnaring bats in the Atlantic Forest at Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. Scientists are probing the mysteries of bat immune systems and investigating strategies to minimize contact between humans and domestic animals with bats and other wild animals. (AP Photo/Silvia Izquierdo)

A researcher for Brazil's state-run Fiocruz Institute places into a cloth bag a bat captured in the Atlantic Forest at Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. Bats are a diverse group, with more than 1,400 species flitting across every continent except Antarctica. (AP Photo/Silvia Izquierdo)

Researchers work in a state-run Fiocruz Institute laboratory at Pedra Branca state park, near Rio de Janeiro, Brazil, Tuesday, Oct. 29, 2020. Their goal is to identify other viruses that may be highly contagious and lethal in humans, and to use that information to devise plans to stop them from ever infecting people. (AP Photo/Silvia Izquierdo)

A bat hangs from a branch outside Brazil's state-run Fiocruz Institute at Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. Bats are thought to be the original or intermediary hosts for multiple viruses that have spawned recent epidemics, including COVID-19, SARS, MERS, Ebola, Nipah virus, Hendra virus and Marburg virus. (AP Photo/Silvia Izquierdo)

A researcher for Brazil's state-run Fiocruz Institute weighs a bat, contained in a cloth bag, that was captured in the Atlantic Forest at Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. Bats are thought to be the original or intermediary hosts for multiple viruses that have spawned recent epidemics, including COVID-19, SARS, MERS, Ebola, Nipah virus, Hendra virus and Marburg virus. (AP Photo/Silvia Izquierdo)

A researcher for Brazil's state-run Fiocruz Institute takes an oral swab sample from a bat captured in the Atlantic Forest, at Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. Teams of researchers around the globe are racing to study the places and species from which the next pandemic may emerge. It's no coincidence that many scientists are focusing attention on the world's only flying mammals — bats. (AP Photo/Silvia Izquierdo)

A researcher for Brazil's state-run Fiocruz Institute, wearing protective gear, transports captured monkeys to a holding area, at Pedra Branca state park, near Rio de Janeiro, Tuesday, Oct. 29, 2020. Researchers at the institute collect and study viruses present in wild animals — including bats, which many scientists believe were linked to the outbreak of COVID-19.  (AP Photo/Silvia Izquierdo)

A monkey, captured by researchers of Brazil's state-run Fiocruz Institute, looks out from a cage, at Pedra Branca state park, near Rio de Janeiro, Tuesday, Oct. 29, 2020. The institute collects and studies viruses present in wild animals. (AP Photo/Silvia Izquierdo)

A researcher for Brazil's state-run Fiocruz Institute photographs a bat captured in the Atlantic Forest, at Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. Teams of researchers around the globe are racing to study the places and species from which the next pandemic may emerge. It's no coincidence that many scientists are focusing attention on the world's only flying mammals — bats. (AP Photo/Silvia Izquierdo)

Bats, inside cloth bags, hang from a line at Brazil's state-run Fiocruz Institute at Pedra Branca state park, near Rio de Janeiro, Tuesday, Nov. 17, 2020. A 2019 study found that of viruses originating from the five most common mammalian sources — primates, rodents, carnivores, ungulates and bats — those from bats are the most virulent in humans. (AP Photo/Silvia Izquierdo)