Possiblity of contrating disease during defending self

Husband was involved in argument with sister's boyfriend who has been forbidden from entering our house that we rent to his parents (we don't reside there but are often called upon by his elder parents for assistance). Police called after slight scuffle (husband had confirmed, 2 days later, 2 fractured ribs and high possibility of a concussion by emergency room techs - he didn't go right in to emergency room as he felt pain was just a minor issue from scuffle - my husband didn't hit boyfriend at all - after restraining the boyfriend from futher attacks, simply called the police), Harrassment charges on both parties. Considering mutually dropping charges, however we have some concern about the possibility of catching hepatitis from the sister's boyfriend. Cannot confirm disease as it takes 1-3 weeks to develop in human body, however police officers asked us to call tomorrow morning re dropping charges. If harassment charges are dropped and it is confirmed later that disease has been spread to my husband, do we have any legal rights to go back after the indiviudal?