On views of morality that I find plausible, your virus wouldn't stop us judging that certain things (cheating, inequity . . .) are wrong, even though it would probably mean that we were not longer motivated to avoid them. (But on other 'non-cognitivist' views, which tie moral judgements to our motivations, this would mean that we would cease even to judge that those things are wrong.)

A loss of emotional reactions is likely to undermine more than just moral motivation. In his book 'Descartes' Error' Anthony Damasio argues that without emotional reactions there would be no effective decision-making of any kind. Damasio describes a patient with severe damage to his prefrontal lobes. This patient could see the pros and cons of alternative courses of action (such as Tuesday versus Wednesday for his next appointment) but would discuss the options interminably without ever reaching a decision. This suggests that emotional reactions to envisaged situations are an essential part of the mechanism by which we make any choices.

And it is not only non-cognitivists who would believe that it would make a moral difference if humans did not experience certain emotions.

For example, suppose that I were a cognitivist hedonist, act Utilitarian. I believe that one ought always to perform the act that produces the greatest balance of pleasure over pain, and I believe that that moral principle is true independently of my or anyone else’s commitment to it. For me, it would make a great deal of difference what sorts of emotions human beings experienced in different circumstances, since the amount of pain or pleasure that anyone feels as a result of my actions will depend, at least in part, on their emotional attachments.

Or suppose that I am a cognitivist virtue theorist of the following variety: I believe that I ought to live my life in such a way that I live a good and meaningful life, and I believe that a corresponding normative principle applies to everyone else. They too ought to live their lives in such a way that they live good and meaningful lives. Let’s suppose also that I believe that, to achieve this end, I need to cultivate certain sturdy character traits. I call such traits "virtues". Given my current emotional dispositions and the emotional dispositions of my fellow human beings, some of these character traits are ones that we would recognize as moral: justice, beneficence, friendliness, loyalty. However, if human beings changed– if they no longer were able to form any emotional attachments to other people, but were all content to live in isolation, indeed resented any intrusion into their individual lives, then again, what character traits I should cultivate in myself to live a good and meaningful life would change. On this view, then, depending on human nature, including our emotional nature, different traits would count as virtues.

Emotion-less or emotion-free creatures/beings have been explored in science fiction, including Stanley Kubrick's "2001" and "Star Trek." See what Wikipedia says about the 1956 B&W movie, "Invasion of the Body Snatchers," at http://en.wikipedia.org/wiki/Invasion_of_the_Body_Snatchers.