Filter For Specific Posts

Hello, Thanks for this amazing plugin. This is not only for Echo RSS, but for the other plugins I posses. Please how do I filter for specific keywords? For instance, I'm pulling posts from http://feeds.bbci.co.uk/news/health/rss.xml however I would only like posts with certain key words i.e. blood test, coronavirus, etc. How do I get this to only pull down news that is about this topics?