Former CDC Director Dr. Robert Redfield warned last week on NewsNation:

"I'm obviously most worried about bird flu. Right now, it takes five amino acid changes for it to be effectively infecting humans. That's a pretty heavy species barrier - but this virus is already in 26 mammal species, as you most recently saw cattle. But in the laboratory, I could make it highly infectious for humans in just months." 

Redfield continued: 

"That's the real threat. That's the real biosecurity threat that these university labs are doing bio-experiments that are intentionally modifying viruses - and I think bird flu is going to be the cause of the Great Pandemic - where they're teaching these viruses to be more infectious for humans." 

Here's Redfield's interview: