Passing Headers to a Route Invoked via Proxy

I have a route (A) that invokes a bean. In the bean I am using the @Produce
annotation to proxy to an endpoint associated with route B.

When the endpoint for route B is invoked, camel creates a new exchange for
it and sets the body to the BeanInvocation from the proxy call.

But route B needs information that is stored in the headers of the exchange
from route A.

What is the best way to get information from the headers of the exchange for
route A transferred to route B?