I think EmailAuthor.jsp does not support many recipient so this will not work for you.

You should write custom code for sending mass emails to all Patient__c related to Disease__c.

I found one useful link that explains how EmailAuthor.jsp works.

Please read through and see if you can use p4 ( CC) & p5 (BCC) parameters to send email to many Patients.

http://salesforcewizard.wordpress.com/2014/01/08/great-url-hack-meet-the-chatter-publisher-action/