Viral Respiratory Infections: Upper and Lower Respiratory Tract Infections.

Respiratory infections are a major health concern and are divided into upper and lower respiratory tract infections. Upper respiratory tract infections are mostly viral and self-limiting; billions of cases occur globally each year. Lower respiratory tract infections such as pneumonia and bronchitis can cause significant illness, especially in children, older adults, and individuals with comorbidities or immunocompromise. In 2021, lower respiratory tract infections caused more than 2 million deaths globally, mainly in low- and middle-income countries. Preventive measures include hand hygiene, masks, ventilation, vaccination, and pharmacologic prophylaxis. Vaccines for influenza, COVID-19, and respiratory syncytial virus infection are available in the United States. Vaccines for human metapneumovirus, parainfluenza viruses, and human rhinovirus are in development. Differentiating viral from bacterial infections is challenging. Biomarkers such as procalcitonin and C-reactive protein can guide antibiotic use. Treatment of viral respiratory infections is mainly supportive, with use of intranasal decongestants and nonsteroidal anti-inflammatory drugs. Early use of zinc and vitamin C may shorten symptom duration; evidence for vitamin D, probiotics, and echinacea varies. Judicious antibiotic use prevents antimicrobial resistance, and treatment with no or delayed antibiotics is often sufficient. Most viral respiratory infections resolve in 1 to 2 weeks, although coughing may persist longer. Patient education about self-care, prevention, and antibiotic use is key to better outcomes and reduced health care burden.