Some people have flu-like symptoms. There can be chills, body aches, fatigue and fever. Pulmonary and nasal passages may add a sore throat, sneezing or coughing. Is a virus or bacterial infection causing the symptoms?
⚠️ Use Discretion: Graphic phlegm images.
Coughing Up More Than Air
Coughing is an automatic reflex that begins when nerves called cough receptors sense that something has entered your airways that shouldn’t be there. The force behind a cough occurs because the opening to your windpipe (the glottis), located at the back of your throat, momentarily closes as you exhale.
With the glottis closed, extra pressure builds up in your lungs. When the glottis finally opens, the air explodes out up to 50 miles per hour, helping to dislodge up to 10,000 droplets and foreign particles from your airways. 
There are many reasons for coughing. These include postnasal drip, asthma, GERD, smoking, inhalation of a foreign object, stress, bacterial infections, (pneumonia, pertussis), congestive heart failure, cystic fibrosis, pollution, emphysema, lung cancer, medications, emotional or psychological problems, and tuberculosis.
With irreversable lung damage, Chronic Obstructive Pulmonary Disease is a leading cause of death and illness, mainly associated with emphysema and chronic bronchitis. 
Coughs Warranting a Doctor Visit
An unexplained chronic cough should be examined by an internist or pulmonology doctor. Sometimes influenza can be followed by a more serious lung ailment like bronchitis or pneumonia. Healthcare professionals may perform pulmonary function tests  or analyze a sputum culture. 
A sputum culture is a test to detect and identify bacteria or fungi (plural of fungus) that are infecting the lungs or breathing passages. Sputum is a thick fluid produced in the lungs and in the airways leading there. Do not use a mouthwash prior to the test since antibacterial substances may skew lab results.
Even without a sputum culture by a physician, you may notice signs of more serious illness when clearing your throat by examining the color and texture of phlegm. Color can vary from transparent to shades of yellow, green, brown, and grey depending on the constituents. Phlegm may be a carrier of intestinal parasite larvae.
The color, quantity, and viscosity of your spit speaks volumes about your health. Bloody sputum can be a symptom of serious disease (such as tuberculosis or pneumonia), but can also be a relatively benign symptom of a minor disease (such as acute bronchitis). In the latter case, sputum may be lightly streaked with blood. Coughing up any significant quantity of blood is always a serious medical condition. Any person who experiences this should seek medical attention. 
A non-productive (dry) cough may turn into a productive one, typically associated with a viral upper respiratory tract infection, such as the common cold. Infection causes the mucous membrane of the bronchial tubes to become inflamed and produce thick, sticky mucus. No longer removed by the normal action of the cilia, it clogs up the airways.
Frothy sputum is one of several symptoms that may indicate heart failure, seizures, hypertensive heart disease, pulmonary edema, near drowning, acute mountain sickness, or a rare but potentially deadly infection called (Bubonic, Pneumonic or Septicemic) plague (generally spread from rodents to humans).  When accompanied by choking, gagging, unusual pain, or abnormal heart rhythms, seek emergency care.
Heart failure often causes pulmonary edema. Pressure in the veins going through the lungs starts to rise, forcing fluid into the alveoli. This interrupts normal oxygen movement through the lungs and manifests pink frothy sputum. Diagnosis is confirmed on x-ray of the lungs, which shows increased fluid in the alveolar walls. [7,8]
Acute bronchitis often produces thick discolored phlegm. In some cases phlegm tinged with bloody streaks appears at the outset and lightens over the next few days. In other cases, white mucus gradually discolors. Coagulated phlegm can interfere with breathing and cause chest discomfort.
Productive coughing dislodges phlegm to increase the lungs’ oxygen capacity. There is a mild debate on whether to swallow or spit out phlegm. What is popular in your family? A gastroenterologist recommends expelling into a napkin. This prevents ingestion of potentially harmful bacteria and allows patients to monitor the progression (color) of phlegm.
Without adequate liquid, mucus can dry out into thick green boogers (nasal mucus). Drink plenty of water to lighten mucosal viscosity. An over-the-counter cough syrup with expectorant can help loosen congestion. Those with asthma may also require a nebulizer prescribed by a pulmonologist.
If acute bronchitis does not resolve within a week or if it is accompanied by additional serious symptoms mentioned in this article, see a pulmonology physician, as there may be an underlying bacterial infection or some other disease. When in doubt, contact your doctor.
Regardless of the cause, you will feel better if your lungs are clear of phlegm. Stay hydrated  and get plenty of rest to boost your immune system and remain healthy.
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