Acknowledgements
The authors thank Joe Orlando and Brandon Medeiros for generating
feedstocks, Elizabeth Goodrich, Akshat Gupta, Santosh Rahane for helping
prepare feedstocks, David Casaperalta, Dominic Smith, Alvaro Botero for
performing infectivity assays, Robert Kelly, Thomas Jefferies, David
Bohonak, Ushma Mehta, Herb Lutz and Tom Elich for valuable discussions.
We are grateful to Kate Smith for her careful review of the manuscript.