Resources on treating OCD-like thoughts on loved ones dying?

Fellow therapists,

I've recently noticed that I have a number of clients who are experiencing frequent intrusive and distressing thoughts regarding their loved ones dying. As a result, they often engage in behaviors such as seeking reassurance, being hypervigilant of their loved ones safety, etc. They do not not have the need to engage in rituals beyond this to prevent harm. Some of the individuals have some history of trauma that connects to this fear and some are not directly related to trauma.

I am wondering if anyone can share some resources to assist in treatment to target these symptoms? I am familiar with ERP and CBT, however I have been wanting to find some more specific information on treating this type of fear.

I'd appreciate any reading or trainings that you may be aware of that touch upon this specific type of fear. Thank you in advance!