Viral
Bronchitis
Viral
Bronchitis is inflammation of the large airways that
branch off the trachea (bronchi), usually caused by viral
infection but sometimes initiated by irritation from
a gas or particle.
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Symptoms
of Viral Bronchitis lasting up to 90 days are
usually classified as acute bronchitis; symptoms lasting longer,
sometimes for months or years, are usually classified as chronic
bronchitis. When chronic bronchitis also decreases airflow, it
is considered a defining characteristic of chronic obstructive
pulmonary disease. This chapter discusses acute bronchitis only.
Causes
Viral Bronchitis is caused by virus breeding
in the lungs.
Infectious
bronchitis occurs most often during the winter and is most often
caused by viruses. Even after a viral bronchitis infection
has resolved, the irritation it causes can continue to cause symptoms
for weeks. Infectious bronchitis may also be caused by bacteria,
and it often follows an upper respiratory viral bronchitis
infection. Mycoplasma pneumoniae and Chlamydia pneumoniae often
cause bacterial bronchitis in young adults. Among middle-aged
and older people, Streptococcus pneumoniae, Haemophilus influenzae,
and Moraxella catarrhalis are the most common organisms causing
bacterial bronchitis. Viral bronchitis may be caused by a number
of common viruses, including the influenza virus. A person often
has a combination of bacterial and viral bronchitis.
Smokers
and people who have chronic lung diseases may have repeated attacks
of acute bronchitis because mucus is less able to drain from their
airways. Malnutrition increases the risk of upper respiratory
tract infections and subsequent acute bronchitis, especially in
children and older people. Chronic sinus infection, bronchiectasis,
and allergies also increase the risk of repeated episodes of acute
bronchitis. Children with enlarged tonsils and adenoids may have
repeated episodes of bronchitis.
Irritative
bronchitis (also called industrial or environmental bronchitis)
may be caused by exposure to various mineral and vegetable dusts.
Exposure to fumes from strong acids, ammonia, some organic solvents,
chlorine, hydrogen sulfide, sulfur dioxide, and bromine can also
cause irritative bronchitis.
Symptoms
Infectious bronchitis generally begins with the symptoms of a
common cold: runny nose, sore throat, fatigue, chilliness, and
back and muscle aches. A slight fever (100° to 101° F)
may be present. The onset of cough (usually dry at first) signals
the beginning of acute bronchitis. With viral bronchitis,
small amounts of white mucus are often coughed up. When the coughed-up
mucus changes from white to green or yellow, the condition may
have been complicated by a bacterial infection.
- With
severe bronchitis, fever may be as high as 101° to 102°
F and may last for 3 to 5 days even with antibiotic treatment.
- The
cough is the last symptom to subside and often takes several
weeks or even longer to resolve.
- Viral
bronchitis can damage the epithelial cells lining
the bronchi, and the body needs time to repair the damage.
- Airway
hyperreactivity, which is a short-term narrowing of the airways
with impairment or limitation of the amount of air flowing into
the lungs, is common with acute bronchitis.
- The
impairment of airflow may be triggered by common stimuli, such
as inhaling mild irritants, inhaling cold, outdoor air, or smelling
strong odors. If the impairment of airflow is severe, the person
may be short of breath. Wheezing, especially after coughing,
is common.
Serious
complications, such as acute respiratory failure or pneumonia,
usually occur only in people who have an underlying chronic lung
disease, such as chronic obstructive pulmonary disease or asthma.
Diagnosis
A doctor usually makes a diagnosis of bronchitis based on the
symptoms and the lack of evidence of pneumonia. The doctor may
hear wheezing during the physical examination.
The
doctor may inspect a sample of sputum: clear or white sputum suggests
a viral bronchitis infection; yellow
or green sputum suggests a bacterial infection. If symptoms are
severe, the doctor may order a chest x-ray to exclude pneumonia.
If a cough persists for more than two months, a chest x-ray is
performed to exclude an underlying lung disease, such as lung
cancer.
- Treatment
Cough medicines can be used to suppress a dry, disturbing cough.
However, a cough that produces a lot of sputum usually should
not be suppressed.
- Expectorants
may help to thin secretions and make them easier to cough up.
- Adults
may take aspirin, acetaminophen, or ibuprofen to reduce fever
and general feelings of illness, but children should take only
acetaminophen or ibuprofen, not aspirin.
- People
with acute bronchitis, especially those who have a fever, should
rest and drink enough fluid to keep their urine pale (except
on arising from sleep, when urine is usually darker).
- Antibiotics
are used to treat acute bronchitis that appears to be caused
by a bacterial infection and may be given as a precaution to
people with underlying lung disease, even when there is no evidence
of bacterial infection. Adults may be given amoxicillin, tetracycline,
doxycycline, or trimethoprim-sulfamethoxazole. When Mycoplasma
pneumoniae or Chlamydia pneumoniae is the suspected cause, erythromycin
or doxycycline is usually given.
- Newer
antibiotics, such as several oral cephalosporins (cefaclor,
cefuroxime), azithromycin, clarithromycin, and the newer fluoroquinolones
(levofloxacin, gatifloxacin) are highly effective, but because
of their high cost, they are generally used for more serious
lung infections. For children, amoxicillin is usually given.
When symptoms persist or recur or when bronchitis is unusually
severe, a laboratory culture of coughed-up sputum may show whether
a different antibiotic is needed.
Antibiotics
do not help people with viral bronchitis.
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