In the fall and winter of the year, hospitals tend to fill up with respiratory infections. These come in many varieties. But just so everyone can understand, I think it might be good to give a quick summary of the things that afflict our population.

Often, our friends and family are diagnosed with bronchitis. While it sounds nefarious, it’s really a very vague, catch-all term. And most of the time, it simply means viral upper respiratory infection. Often associated with head colds, it results in cough, sometimes wheezing and shortness of breath, as the upper airway and bronchial tubes are infected and irritated. Although all too many people are treated with unnecessary antibiotics for bronchitis, it usually is self-limited and goes away whether treated or not. Bronchitis is mostly viral, except in some cases of bacterial bronchitis in those with chronic lung disease.

Pneumonia is usually more troublesome. In pneumonia, lung tissue itself is infected and fills with infectious particles, white blood cells and inflammatory fluid. Pneumonia can affect one segment of the lung, multiple segments, and one or both lungs.

Pneumonia can be either viral or bacterial. Typically, it causes fever, chills, shortness of breath, rapid heart rate and chest pain. Patients will cough up clear, yellow or (in classic bacterial pneumonia) green or brown, bloody or rust-colored phlegm.

Fatigue and dehydration, nausea and vomiting can result from either. Indeed, patients with some viral pneumonias can be as sick as those with bacterial infections. Influenza is a classic cause of a viral pneumonia that can result in severe illness, particularly in those who are already very sick, very young or very old. Furthermore, people with influenza can develop bacterial pneumonia after they have influenza.

Our friends and family with chronic lung diseases are often affected adversely this time of year. Weather changes (with associated fluctuations in temperature and humidity), increased exposure to other sick people indoors, smoke and other irritants can worsen the symptoms of those with asthma or COPD (chronic obstructive pulmonary disease). Asthmatics have airways that are very sensitive to stimulants, and may often spasm and fill with fluids. Those with COPD (divided into emphysema or chronic bronchitis) have suffered lung damage from inflammatory diseases, smoking, second-hand smoke, or sometimes pollution.

The treatments of lung inflammation involve inhalers and nebulizers for wheezing, as well as steroids in many cases. Infectious processes like pneumonia, if bacterial, are treated with antibiotics.

Severe cases require hospitalization, and occasionally patients will need to be placed on a ventilator temporarily; pneumonia can be very exhausting and an enormous stress to the body.

Modern medicine is a wonder. Many of these illnesses, in decades and centuries past, were commonly fatal. While it is certainly possible to die of a respiratory illness, we have much more effective ways to treat these afflictions than ever.

That’s a quick overview of a few respiratory illnesses. So next time you hear of someone with bronchitis, pneumonia or COPD, it won’t seem as mysterious.

(PS — Get your flu and pneumonia shots!)