My question involves defamation in the state of: Virginia

I was just made aware that there was a post on a popular forum containing slanderous information about me. The original post falsely states that my brother is having homosexual threesomes with other men. The very next post doesn't mention me by name but says and I will quote: "Yeah ur probably right haha [brothers name] sister is probably doing it too ! lol sheww so nasty can we say std?" I am the only sister that he has. Even though this post doesn't say my name, with me being his only sister is there something I can do? This is false and as you can tell can potentially ruin my reputation. I am absolutely furious at this point. What is my legal recourse? Thank you.