Badge of Infamy by REY, Lester del

Daniel Feldman was a doctor once. He made the mistake of saving a friends life in violation of Medical Lobby rules. Now, hes a pariah, shunned by all, forbidden to touch another patient. But things are more loose on Mars. There, Doc Feldman is welcomed by the colonists, even as hes hunted by the authorities. But, when he discovers a Martian plague may soon wipe out humanity on two planets, Feldman finds himself a pivotal figure. War erupts. Earth is poised to wipe out the Mars colony utterly. A cure to the plague is the price of peace, and only Feldman can find it. (summary by Steven H. Wilson)