poor appetite

fever, headache, nausea, weakness

Influenza, commonly known as the flu, is an infectious disease of birds and mammals caused by an RNA virus of the family Orthomyxoviridae (the influenza viruses). In humans, common symptoms of influenza infection are fever, nausea, vomiting, sore throat, muscle pains, severe headache, coughing, and weakness and fatigue. In more serious cases, influenza causespneumonia, which can be fatal, particularly in young children and the elderly. Sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus. Similarly, the unrelated gastroenteritis is sometimes called "stomach flu" or "24-hour flu". 

left upper quadrant abdominal pain, stomach pain, upper abdominal pain, vomiting

Gastroenteritis involves diarrhoea or vomiting, with noninflammatory infection of the upper small bowel, or inflammatory infection of the colon, both part of the gastrointestinal tract. ... 

poor appetite, stomach pain, vomiting, weakness

irregular menstrual periods, poor appetite, stomach pain, upper abdominal pain

Alcoholism is the consumption of or preoccupation with alcoholic beverages to the extent that this behavior interferes with the alcoholic's normal personal, family, social, or work life. Alcohol consumption caused by alcoholism can result in psychological and physiological conditions, and ultimately in death. Alcoholism is one of the world's most costly drug use problems; with the exception of nicotine addiction, alcoholism is more costly to most countries than all other drug use problems combined. ... 

decreased sexual desire in males, difficulty sleeping, poor appetite, weakness

In everyday language depression refers to any downturn in mood, which may be relatively transitory and perhaps due to something trivial. This is differentiated from Clinical depression which is marked by symptoms that last two weeks or more and are so severe that they interfere with daily living. ... 

nausea, stomach pain, upper abdominal pain, vomiting

Gastritis is inflammation of the gastric mucosa. The word comes from the Greek gastro- meaning of the stomach and -itis meaning inflammation. Depending on the cause, it may persist acutely or chronically. ... 

decreased sexual desire in males, difficulty speaking, poor appetite, weight loss

Clinical depression (also called major depressive disorder, or sometimes unipolar when compared with bipolar disorder) is a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individual's social functioning and/or activities of daily living. Although a low mood or state of dejection that does not affect functioning is often colloquially referred to as depression, clinical depression is a clinical diagnosis and may be different from the everyday meaning of "being depressed." Many people identify the feeling of being depressed as "feeling sad for no reason", or "having no motivation to do anything." One suffering from depression may feel tired, sad, irritable, lazy, unmotivated, and apathetic. Clinical depression is generally acknowledged to be more serious than normal depressed feelings. It often leads to constant negative thinking and sometimes substance abuse. ... 

difficulty swallowing, fever, pain in neck, sore throat

Pharyngitis (far-in-jī' tis) is a painful inflammation of the pharynx, and is colloquially referred to as a sore throat. Infection of the tonsils, tonsillitis may occur simultaneously. ... 

fever, poor appetite, sore throat, white patches in mouth or throat

Strep throat (or "Streptococcal pharyngitis", or "Streptococcal Sore Throat") is a form of Group A streptococcal infection that affects the pharynx. ... 

fever, headache, nausea, vomiting