how will it effect me if my husband had sex with the lady suffering from rheumatoid arthritis?

It shouldnt effect you at all physically.

Physically – not at all. How you are affected emtionally only you know.

It depends on a lot of things: whether her rheumatoid arthritis is caused by an infectious agent, and if it is, whether it can be spread sexually, and if it can be, your genetic and biological susceptibility to the infectious agent.

I wish you would phrase your question differently, cause you seem to say your husband cheated on you. I don’t know about you, but I wouldn’t want to be with a cheater.