Most of the time when you catch a cold or the flu, it runs its course in about a week. That’s how long it takes your body’s immune system to develop the antibodies it needs to kill whichever virus is causing your runny nose, cough, fever, sneeze and overall yucky feeling.
Sometimes, however, those same viruses can spread from your upper respiratory tract — your nose and throat — down to the tubes that carry air to your lungs. Those are called bronchi, and when they also get infected, you have bronchitis.
There are two types of bronchitis:
— Acute bronchitis. This is the most common form of bronchitis. As with your typical cold, symptoms last for about a week, sometimes two. Once it clears, there are typically no lasting problems.
— Chronic bronchitis. Chronic means the disease keeps recurring or never fully heals. Chronic bronchitis is more serious. It usually indicates some type of lung disease, such as asthma. In fact, chronic bronchitis is one of the several conditions, including emphysema, that comprises chronic obstructive pulmonary disease, or COPD.
About 95% of all cases of acute bronchitis are caused by a virus. The other causes include dust, tobacco smoke and other types of smoke, air pollution and chemical fumes that irritate the breathing passages.
Viruses That Cause Bronchitis
According to the National Library of Medicine, the viruses that cause bronchitis are the same ones that cause other respiratory diseases. The most common viruses, and the typical upper respiratory infection they cause, are:
— Rhinovirus (common cold).
— Parainfluenza viruses (croup).
— Adenovirus (respiratory disease).
— Influenza viruses A and B (influenza).
Bronchitis, like these other diseases, is contagious, because the viruses spread easily from person to person. They can spread when an infected person coughs, sneezes or talks closely to another person, producing droplets of mucus or saliva that carry the germ. Viruses also can live on an infected object, like a doorknob or eating utensil, for anywhere from a few hours to up to two days or so — and infect another person who happens to touch that object and then touch his or her eyes, nose or mouth.
The virus is especially hard to contain because of what is known as its incubation period. This is defined as the amount of time between when the virus enters your body and when it begins to cause symptoms. The virus needs to “incubate” and make enough copies of itself before your body notices it and begins to fight it off, which is what causes the coughing, sneezing and yuckiness. During that time, people don’t know they are sick, but they still spread the germ everywhere they go.
The incubation period can differ significantly depending on the cause, says Dr. MeiLan K. Han, professor of internal medicine in the division of pulmonary and critical care medicine at the University of Michigan Health System and director of the Michigan Airways Program.
The National Library of Medicine reports the following incubation periods for the most common bronchial viruses:
— Rhinovirus: eight to 10 hours.
— Parainfluenza viruses: two to six days.
— Adenovirus: two to 14 days.
— Influenza viruses A and B: eight to 14 days.
Other viruses, though less common, also cause lower respiratory infections. In children, especially those younger than two, respiratory syncytial virus, or RSV, can cause bronchiolitis, affecting smaller air tubes deeper in the lungs, called the bronchioles. The incubation period for RSV is four to five days, says Dr. Cedric “Jamie” Rutland, a pulmonary and critical care physician and assistant clinical professor at the University of California–Riverside. A virus called coronavirus can cause bronchitis and other lower respiratory tract infections in adults. Its incubation period is about 3.2 days, he says.
Thus, if you start to feel sick on a Monday, you could theoretically count backward to figure out when you were infected. But of course you would need to know which virus you have, and doctors rarely test for that unless the case is so severe and lasts for so long that more drastic treatments are necessary.
So why do incubation periods matter?
Rutland says it can be helpful to understand when your child or you got sick. “I believe patients need to understand the pathology because it’s their body, and they need to understand how their body works,” he says. Rutland has seen this kind of knowledge help: “I think when patients know how their body works, their symptoms actually reduce. It’s pretty funny, and I cannot explain it, but they tend to feel better about their illness when they know what the illness entails.”
State of mind is important because there is no way to treat a viral infection itself. ( Antibiotics are useless against viruses.) Doctors can only recommend treatments for the symptoms, which include resting, drinking plenty of fluids and taking pain relievers. “In an individual without underlying lung disease, viral bronchitis is likely to resolve on its own,” Han says.
However, she adds, “Further complicating matters, sometimes viral infections can even then lead to secondary bacterial infections.” But this happens only occasionally. Bacterial infections typically require treatment with antibiotics. (This is not an indication of chronic bronchitis, which is usually the result of smoking or exposure to air pollutants.)
The best ways to avoid catching a virus that causes bronchitis are exactly the same as avoiding a common cold, the Mayo Clinic advises:
— Avoid close contact with people who have a respiratory illness.
— Wash your hands often or use an alcohol-based hand sanitizer.
— Avoid touching your eyes, nose and mouth.
— Get an annual flu shot.
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