Flu is a very common medical condition that we see frequently in the wintertime. Frequently, people have high fevers, muscle aches, cough and vomiting. Things that would prompt an ER visit would be when you can’t keep any fluid or liquids or food down and you have persistent vomiting. If you have a lot of trouble breathing. If you have changed mentation and you’re having trouble thinking. That, or if you have any chronic medical conditions. Also, people who are extreme in age either really young or really old frequently can get very sick with the flu. So you need to seek quick emergent treatment if you have any of those situations.