As far as suing your husband is concerned, the better course would probably be to pursue the matter as a divorce case or, if you don't want a divorce, then as a suit for separate maintenance.
Under the circumstances that you have described, you could file a fault-based divorce action in the Circuit Court on the grounds of adultery, cruelty and constructive desertion, and actual desertion (anyone of those grounds alone would entitle you to a divorce, though it is my practice to include in the initial pleadings any alternate basis that may be available under the facts). In your Complaint for Divorce you would want to include a request for the following types of relief: spousal support (both pendente lite and permanently), sole and exclusive use of the marital residence (if there is one), equitable distribution of property and debts, maintenance of health insurance (if any), for a monetary award (in part to cover the debts you have incurred from this illness he caused), maintenance of martial property pending suit, attorney's fees, and "any and all other equitable relief to which you may be entitled".
Alternatively, you could file a Suit for Separate Maintenance in the Circuit Court or a Petition for Supposal Support in the Juvenile & Domestic Relations District Court. In that type of action you could request support, exclusive use of the marital residence, maintenance of health insurance, and such other equitable relief to which you may be entitled. The court in that type case could not grant a divorce, divide property and debt, or grant a monetary award.
As far as the girlfriend is concerned, the only type of action I can think of for you to pursue would be a tort case -- basically seeking damages for personal injury. However, I think you might have a tough haul with that one. The biggest hurdle is the fact that the girlfriend did not sleep with you and give you a disease (or diseases) -- she slept with your husband and then he slept with you. In such a situation, your husband was an intervening force. Also, you would likely have to prove that she knew that she had the disease when she slept with your husband, did not disclose it to him, that she had a duty to inform him, breached that duty, and then intentionally gave it to him or did it with reckless disregard. THEN, you would have to prove that she KNEW or reasonably should have known that he would then have unprotected sexual relations with you and an injury to you would result. In short, the problem with suing her is that BUT FOR YOUR HUSBAND's SUBSEQUENT ACTIONS the injury to you would not have occurred. However, you should consult with a personal injury attorney regarding this particular matter.
As regards the case against your husband, I would defintely recommend that you get an attorney to represent you or, if you cannot afford one, then try to get some pro bono assistance through legal aid or the local bar association in your area.
This response does not create an attorney-client relationship and is intended for general information purposes only.
You may want to file for the divorce, and in the process obtain your husband's medical records to see what he told his doctor about how he contracted the disease(s). Then, you may be able to bring the girlfriend in on a deposition (because she is the 'co-respondent'- the person with whom your husband committed adultery) and ask her about how and when she found out that she got the disease. Once you have that evidence, you will be in a better position to decide whether or not to sue her, but the better course would be to present this evidence to the court in your divorce and ask for life-time spousal support.
Legal issues often depend on the specific facts in any given case or situation. Please do NOT utilize the information you receive as either a binding legal opinion in your case, nor presume that I am your counsel because I've answered a question you had. Any legal representation is accomplished by written contract ONLY, signed by each of us.
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