From the Guidelines
Viral respiratory infections are typically characterized by a self-limited disease course with symptoms peaking within 3 days and resolving within 10 to 14 days, whereas bacterial infections are believed to complicate only 0.5% to 2.0% of these events and often present with more severe symptoms. The key characteristics of viral respiratory infections include cough, sneezing, rhinorrhea, sore throat, and nasal congestion, with symptoms gradually declining over time 1. In contrast, bacterial infections often develop more suddenly or follow a viral illness, producing thick, colored nasal discharge or sputum, and causing higher fevers.
Some important points to consider when differentiating between viral and bacterial respiratory infections include:
- Nasal purulence alone does not indicate a bacterial infection, as discolored nasal discharge is a sign of inflammation and not specific for infection 1
- The coloration of nasal discharge is related to the presence of neutrophils, not bacteria 1
- Normal transport of mucus requires robust ciliary action, which is impaired in viral respiratory infections due to epithelial disruption, edema, and excessive mucus production 1
- Management of viral respiratory infections is primarily directed toward relief of symptoms, using palliative medications such as analgesics, anti-inflammatory agents, nasal saline, decongestants, antihistamines, mucolytics, cough suppressants, and topical or oral corticosteroids 1
It is essential to note that antibiotics are not recommended for treating viral respiratory infections, as they are ineffective for viral illness and do not provide direct symptom relief 1. Instead, symptom relief can be achieved through the use of palliative medications, and the decision to use topical intranasal steroids should be based on patient preference, given their modest clinical benefit and low risk of adverse events 1.
From the FDA Drug Label
Of the 452 influenza-infected subjects, 67% were infected with influenza A and 33% with influenza B Efficacy in this trial was determined by the time to alleviation or resolution of influenza signs and symptoms, measured by a composite endpoint that required the following four individual conditions be met: i) alleviation of cough, ii) alleviation of coryza, iii) resolution of fever, and iv) parental opinion of a return to normal health and activity The efficacy endpoint for all of these trials was the incidence of laboratory-confirmed clinical influenza defined as meeting all the following criteria (all signs and symptoms must have been recorded within 24 hours): oral temperature greater than or equal to 99.0ºF (37. 2ºC), at least one respiratory symptom (cough, sore throat, nasal congestion), at least one constitutional symptom (aches and pain, fatigue, headache, chills/sweats), and either a positive virus isolation or a four-fold increase in virus antibody titers from baseline
The characteristics of viral respiratory infections mentioned in the label include:
- Fever: at least 100ºF
- Respiratory symptoms: cough, coryza
- Constitutional symptoms: aches and pain, fatigue, headache, chills/sweats
- Laboratory confirmation: positive virus isolation or a four-fold increase in virus antibody titers from baseline
There is no information in the label about the characteristics of bacterial respiratory infections. 2
From the Research
Characteristics of Viral vs Bacterial Respiratory Infections
- Viral respiratory infections can predispose individuals to bacterial infections, and co-infections tend to have worse outcomes 3
- Distinguishing between viral and bacterial respiratory infections can be challenging, but biomarkers such as procalcitonin, C-reactive protein, and neopterin can be useful in differentiating between the two 4
- Amoxicillin treatment may reduce symptom severity and illness deterioration in patients with bacterial or combined bacterial and viral infections, but not in those with strictly viral infections 5
- Rapid diagnostic strategies and syndromic approaches are essential for identifying the causative viral pathogens of respiratory tract infections and selecting the correct management and treatment 6
- Clinical differentiation between viral and bacterial upper respiratory tract infections is difficult, but certain conditions such as acute tracheitis, laryngitis, and common cold are normally caused by viral agents 7
- The use of antibiotics is not recommended for patients with viral upper respiratory tract infections, unless there is a high suspicion of bacterial infection 7
- Biomarkers such as procalcitonin, C-reactive protein, and neopterin can be used in combination to improve the discriminatory power in delineating bacterial versus viral etiology in lower respiratory tract infections 4