This appears to be connectivity issues entirely to/from the Internet or other EC2 regions from a single availability zone in us-east-1. The intra-AZ networks within us-east-1 have remained available during the event. One of the AZs we use was affected, but no external traffic flows to it. I noticed this because an auto-scale group was trying to bring up instances inside of the affected zone (our us-east-1a) and was unable to contact a server outside of AWS.