The 2 Most Common Causes of Bronchitis–and How to Avoid Them

The very same viruses that cause the flu or a cold can make their way to your chest and lungs.

Winter is prime time for the coughing, phlegm, fatigue, and general unpleasantness of acute bronchitis. Viruses are by far the most common cause of the illness, which typically goes away in a week or so (although the cough can linger). And–'tis the season–it's usually the very same viruses that cause the flu or a common cold that give you bronchitis, too.

But there can be other culprits. Here are the most common causes of bronchitis you should know about.


Bronchitis often starts as a cold or the flu. Basically, the infection digs deeper into your respiratory system, namely the bronchial tubes that transport air to and from your lungs. That's why acute bronchitis is sometimes also called a chest cold. If the infection moves even further down, into the lung tissue, you may end up with pneumonia.

"It's fairly common that bronchitis starts off as a cold," says Sean Drake, MD, a general internist with Henry Ford Health System in Sterling Heights, Michigan. "A lot of times people will say that they had a cold that settled into their chest."

Or the flu. "One of the more dangerous viruses is influenza," says Leann Silhan, MD, a pulmonary disease expert at UT Southwestern in Dallas. "You can get infection with flu and not have bronchitis, but often you can develop bronchitis."

The flu, of course, is caused by the influenza virus, while colds–and subsequent bronchitis–can be blamed on multiple villains: rhinovirus, adenovirus, parainfluenza, respiratory syncytial virus, coronavirus, and others.

It's not always clear why some colds move on to bronchitis and some don't, but it's usually a combination of the type of virus and the health of the patient, says Dr. Silhan. "There are a lot of different strains of every virus out there," she says. "Some are more virulent than others. Rhinovirus tends not to cause bronchitis very frequently. RSV more commonly causes bronchitis."

At the same time, some people exposed to a particular virus won't get sick at all while others get the smallest exposure and fall ill. That can depend on viral load–how much of the virus you end up with.

The strength of your immune system also has a lot to do with it. Especially vulnerable are people who have organ transplants and are taking immunosuppressant drugs. People who are over 65, under 2, or have chronic health conditions like diabetes, asthma, or COPD are also at higher risk for bronchitis, as are pregnant women. Even people with acid reflux are prone to getting bronchitis.


According to the American Lung Association, bacteria cause fewer than 10% of all cases of bronchitis. Three, in particular, are usually to blame, says Dr. Silhan: Haemophilus influenzae (not to be confused with the flu virus), Moraxella catarrhalis, and Streptococcus pneumoniae (the same bacterium that causes strep throat).

Other bacteria that can cause bronchitis include Mycoplasma pneumoniae, Chlamydia pneumoniae (not the same as the bacterium that causes the sexually transmitted disease), and Bordetella pertussis (which also causes whooping cough).

Bacterial bronchitis is most common in people with chronic lung diseases like COPD. Other groups that are at higher risk include "the elderly; young kids; people who have other major conditions like cancer, diabetes, or asthma; and smokers," says Traci Gonzales, a spokesperson for the American Lung Association and a nurse practitioner with UTHealth McGovern Medical School at Houston.

People with these conditions have damaged lung tissue, so "these bacteria can settle in as an infection much more easily," says Dr. Silhan.

Bacterial bronchitis is not necessarily more severe than viral bronchitis, especially bronchitis caused by influenza. "It really depends on the patient," says Gonzales.

Although smokers are more prone to bronchitis because of damage to their respiratory systems, cigarette smoke–or other irritants like fumes or fragrances–cannot cause bronchitis. "Bronchitis really implies an infection," says Dr. Drake. "When someone's a smoker, that first layer of protection gets destroyed, so you can get infections with bacteria or viruses," adds Dr. Silhan.

When to call a doctor

Most cases of bronchitis, even bacterial bronchitis, go away on their own with rest, plenty of fluids, and nonsteroidal anti-inflammatory drugs (NSAIDs) to ease pain. Antibiotics usually aren't needed for bacterial bronchitis unless it goes on for longer than two or three weeks, says Dr. Drake.

There are signs that you should see a doctor, though. "If you're feeling chest tightness, meaning it's hard for you to breathe, if you are coughing constantly and can't even perform normal daily activities because the cough is so severe, if you're lethargic, or if you're running a fever, you should get that checked out," says Gonzales. "High-risk groups should also be seen earlier rather than later."

The best way to avoid having to see a doctor is to not get sick to begin with. The number one way to prevent bronchitis? Get your flu vaccine. Washing your hands is a close second. Scrub well and often, with either soap and water or alcohol-based sanitizers when a sink isn't available.

Was this page helpful?
Related Articles