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Most scientists never heard of DEFUSE
The document
The DEFUSE proposal came from EcoHealth Alliance, the nonprofit run by Peter Daszak that did virology research. The group DRASTIC, a loosely affiliated set of scientists who come together and share information, uncovered the document three years after COVID began. It is a real document that anyone can download.
What it described
The proposal connects a top US virologist with Zhengli, the Wuhan virologist known as the bat lady. It describes inserting a cleavage site at the S1S2 junction of a bat coronavirus, because the authors thought it would make the virus more viral in animals.
The survey
In a survey, scientists were asked what they thought caused COVID, and those who answered animal spillover were asked whether they had heard of DEFUSE. Only 22 percent had, and 78 percent had never heard of it.
Why does the S1S2 junction matter?
The spike protein that coronaviruses use to enter cells has two parts: S1, which binds a receptor on the host cell, and S2, which drives the fusion of virus and cell membranes. The junction between them is where host enzymes cut the spike to prime it for entry. SARS-CoV-2 has a furin cleavage site at that junction, and furin is an enzyme found in many human tissues. Some other coronaviruses, including the cold virus OC43 and MERS-CoV, have comparable sites.
How do bat viruses reach people?
A virus must first bind receptors on human cells, and for SARS-CoV-2 and the original SARS virus that receptor is ACE2. Many bat coronaviruses bind poorly to human ACE2, so a jump can involve an intermediate animal host. The 2003 SARS virus was found in masked palm civets in live-animal markets, and MERS was found in dromedary camels. Genetic changes in the spike protein can change how well it binds a new host's receptors.
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