To meet the requirements for the healthcare company's workload that is moving to the AWS Cloud, the network engineer should take the following steps:
Use AWS Direct Connect with MACsec support for connectivity to the cloud to ensure that all data to and from the on-premises environment is encrypted in transit (Option D).
Use Gateway Load Balancers to insert third-party firewalls for inline traffic inspection to inspect all traffic in the cloud before it is allowed to leave (Option E).
Configure AWS Shield Advanced and ensure that it is configured on all public assets to secure components exposed to the internet against DDoS attacks and provide protection against financial liability for services that scale out during a DDoS event (Option F).
These steps will help ensure that all data is encrypted in transit, all traffic is inspected before leaving the cloud, and components exposed to the internet are secured against DDoS attacks.

An Application Load Balancer (ALB) can be used to route traffic to multiple target groups based on the URL in the request. The ALB can be configured with an HTTPS listener to ensure all traffic uses HTTPS. TLS processing can be offloaded to the ALB, which reduces the load on the web server. Path-based routing rules can be used to route traffic to the correct target group based on the URL in the request. The X-Forwarded-For request header can be included with traffic to the targets, which will allow the web server to know the user's IP address and keep accurate logs for security purposes.

Ref: https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html
"A NAT gateway can support up to 55,000 simultaneous connections to each unique destination. This limit also applies if you create approximately 900 connections per second to a single destination (about 55,000 connections per minute). If the destination IP address, the destination port, or the protocol (TCP/UDP/ICMP) changes, you can create an additional 55,000 connections. For more than 55,000 connections, there is an increased chance of connection errors due to port allocation errors. These errors can be monitored by viewing the ErrorPortAllocation CloudWatch metric for your NAT gateway. For more information, see Monitoring NAT Gateways Using Amazon CloudWatch."