Respiratory infections are common and generally cause self-limited illnesses in healthy, immunocompetent hosts. Viruses account for a significant percentage of respiratory diseases, but bacteria may be associated with respiratory infections. Although respiratory illnesses are frequently mild, viruses may cause significant morbidity and mortality in immunocompromised hosts (eg, transplant recipients, patients with underlying malignancies).
Bacterial pathogens (Bordetella, Chlamydia, and Mycoplasma) are the common root cause of upper respiratory infections. Clinical manifestations of upper respiratory infections caused by bacterial pathogens are quite similar, however, pertussis is characterized by typical spasmodic cough, pauses before deep but difficult breath, gasping for breath, and vomiting at the end of an attack. Other pathogens are linked to pharyngitis, tracheobronchitis, and rarely pneumonia.
Influenza viruses and respiratory syncytial virus cause a clinically indistinguishable syndrome, characterized by fever, cough, headache, and general malaise. Nowadays heavily spread Covid-19 disease is characterized by the same symptoms. RSV and parainfluenza are a leading cause of respiratory illness in young children, parainfluenza and adenovirus can cause more severe lower respiratory diseases like pneumonia. Due to almost indistinguishable symptoms caused by viral pathogens is recommended to test patients for the whole panel to discover the source of infections and start proper treatment.