Diarrhea is a sign that can be a part of many different types of conditions. Food poisoning usually refers to eating food which has been contaminated with some bacteria or toxins that can make you feel very sick. Food poisoning usually causes symptoms such as diarrhea or vomiting
within 12 hours of ingesting the food and only lasts another 24 to 36 hours. You symptoms 5 days out suggest that this is not food poisoning. One possibility as you stated is that you have caught a virus that infects the GI tract. This is one of the most common causes of an upset stomach, diarrhea, nausea and sometimes vomiting that can go on for a few days. The diarrhea and vomitus are almost always without blood. The GI viruses can be caught from a variety of different sources and the salad you ate is not necessarily the culprit. If you have bloody diarrhea, this suggests a different type of infection such as that with a GI bacteria. This is usually accompanied by fever and generalized feeling of being very sick.
Since you have been sick for 5 days, you really should be seen by a doctor
. I suggest that you schedule an appointment with your primary care physician
for further workup and treatment.