<em>Mononucleosis</em> is an infection, more common in children than adults. the general symptoms are fever, swollen neck lymph nodes, between others. Sometimes even affecting other organs of the body, like the liver.
The guilty of all this infection is the <u><em>Epstein–Barr</em></u><u> virus</u> that it is primarily spread by saliva. Since its a really contagious bacteria can be easily transmitted by an infected person who uses or drink from the water bottle to other ones.
Always say no never consume anything that you are not sure of what the substance is and in this situation just don't go you can never be to safe at least that's what I would do anyway
