AUTHOR: Fred F. Ferri, MD
Epidemiology & Demographics
- Highest incidence in smokers, older adults, and young children and during winter months.
- In the U.S. there are nearly 30 million ambulatory visits annually for cough, leading to more than 12 million diagnoses of “bronchitis.”
- Acute lower respiratory tract infection is the most common condition treated in primary care.
Physical Findings & Clinical Presentations
- In most cases, acute bronchitis begins with signs and symptoms typical of the common cold syndrome (nasal congestion, sore throat), followed shortly by the onset of cough
- Cough, usually worse in the morning, often productive; mainly caused by transient bronchial hyperresponsiveness
- Low-grade fever
- Substernal discomfort worsened by coughing
- Postnasal drip, pharyngeal injection
- Rhonchi that may clear after cough, occasional wheezing
- Various host factors (age, immune status, smoking, underlying medical conditions) can influence illness severity and clinical presentation
- In mild cases, the illness lasts only 7 to 10 days, whereas in others, cough may persist for up to 3 wk or longer
Etiology
- Viral infections are the leading cause of bronchitis (rhinovirus, influenza virus, adenovirus, respiratory syncytial virus)
- Atypical organisms (Mycoplasma, Chlamydia pneumoniae)
- Bacterial infections (Bordetella pertussis, Haemophilus influenzae, Moraxella, Streptococcus pneumoniae)
- Table 1 summarizes viral and bacterial causes of acute bronchitis
TABLE 1 Viral and Bacterial Causes of Acute Bronchitis
| Pathogen | Seasonality | Comments |
|---|---|---|
| Influenza viruses | Winter | Local epidemics last 6-8 wk during which clinical illness of cough and fever has high predictive value; laboratory diagnosis readily available; early neuraminidase inhibitor therapy effective |
| Rhinoviruses | Fall and spring | Most frequent cause of common cold syndrome; immunity is serotype specific |
| Coronaviruses | Winter to spring | Cause common cold syndrome; newer strains are difficult to culture and require RT-PCR for diagnosis |
| Adenoviruses | Year round, winter epidemics | High attack rates in closed populations such as persons living in military barracks or college dormitories; serotype-specific immunity |
| Respiratory syncytial virus (RSV) | Late fall to early spring | Attack rates approach 75% in neonates, 3%-5% in adults; associated with wheezing in all age groups; rapid antigen test accurate in children but requires culture or RT-PCR to diagnose in adults |
| Human metapneumovirus (hMPV) | Winter to early spring | Associated with wheezing in adults and in infants; difficult to isolate in tissue culture and often requires RT-PCR |
| Parainfluenza viruses | Fall to winter | Similar to RSV and hMPV, parainfluenza viruses are primarily pediatric pathogens but can cause severe acute disease in some adults |
| Measles virus | Year round | Can cause respiratory disease in malnourished children; illness causes transient immune suppression |
| Mycoplasma pneumoniae | Year round, fall outbreaks | Long incubation period (10-21 days) results in staggered epidemic pattern in families; nonproductive persistent cough typical; diagnosed by IgM serology; treated with macrolide, quinolone, or tetracycline antibiotics |
| Chlamydia pneumoniae | Year round | Associated with sinusitis; diagnosis by RT-PCR not readily available |
| Bordetella pertussis | Year round | Severe illness in nonimmunized children; illness milder in partially immune adults; can be associated with prolonged cough; adults are often reservoirs for epidemics; early therapy with antibiotics can reduce spread |
IgM, Immunoglobulin M; RT-PCR, reverse-transcriptase polymerase chain reaction.
From Bennett JE et al: Mandell, Douglas, and Bennett’s principles and practice of infectious diseases, ed 8, Philadelphia, 2015, Saunders.
