USMLE Guide: Respiratory Infections

Introduction

Respiratory infections refer to a group of infectious diseases that affect the respiratory system, including the upper and lower airways. These infections can be caused by various pathogens, such as viruses, bacteria, fungi, and parasites. Understanding the key features, diagnostic approaches, and management strategies for respiratory infections is crucial for medical professionals preparing for the United States Medical Licensing Examination (USMLE). This guide aims to provide an overview of respiratory infections, focusing on important concepts and key points to remember.

Table of Contents

1. Upper Respiratory Tract Infections
   • Common Cold
   • Sinusitis
   • Pharyngitis
2. Lower Respiratory Tract Infections
   • Influenza
   • Pneumonia
   • Tuberculosis
3. Key Points to Remember
4. Conclusion

1. Upper Respiratory Tract Infections

Common Cold

• Most common viral infection affecting the upper respiratory tract.
• Caused by rhinoviruses, coronaviruses, or respiratory syncytial virus (RSV).
• Presents with symptoms like rhinorrhea, sore throat, cough, and low-grade fever.
• Usually self-limited and managed symptomatically.
• Hand hygiene and respiratory etiquette are important preventive measures.

Sinusitis

• Inflammation of the paranasal sinuses.
• Often follows a viral upper respiratory infection or allergic rhinitis.
• Bacterial superinfection may occur.
• Presents with facial pain, purulent nasal discharge, and congestion.
• Diagnosis based on clinical presentation, but imaging may be required.
• Antibiotics may be necessary in bacterial sinusitis.

Pharyngitis

• Inflammation of the pharynx.
• Commonly caused by viruses (e.g., adenovirus, Epstein-Barr virus) or group A beta-hemolytic streptococcus (GABHS).
• GABHS pharyngitis requires antibiotic treatment to prevent rheumatic fever and other complications.
• Centor criteria can help assess the need for throat culture and antibiotic therapy.

2. Lower Respiratory Tract Infections

Influenza

• Highly contagious viral infection affecting the respiratory system.
• Caused by influenza viruses A, B, or C.
• Presents with fever, cough, sore throat, myalgia, and fatigue.
• Annual vaccination is recommended for prevention.
• Antiviral drugs (e.g., oseltamivir) may be used for treatment and prophylaxis.

Pneumonia

• Inflammation of the lung parenchyma.
• Community-acquired pneumonia is commonly caused by Streptococcus pneumoniae.
• Hospital-acquired pneumonia is often caused by gram-negative bacteria (e.g., Klebsiella pneumoniae).
• Presents with fever, cough, dyspnea, and focal chest findings.
• Chest x-ray and sputum culture are often required for diagnosis.
• Antibiotics should be initiated promptly based on the suspected pathogen.

Tuberculosis

• Chronic bacterial infection caused by Mycobacterium tuberculosis.
• Often affects the lungs but can involve other organs.
• Presents with cough, weight loss, night sweats, and hemoptysis.
• Mantoux tuberculin skin test and interferon-gamma release assays aid in diagnosis.
• Treatment involves a combination of antibiotics (e.g., isoniazid, rifampin) for an extended duration.

3. Key Points to Remember

• Upper respiratory tract infections are commonly viral and usually self-limited.
• Sinusitis may require antibiotics for bacterial superinfection.
• GABHS pharyngitis requires antibiotic treatment to prevent complications.
• Influenza vaccination and antiviral drugs play a crucial role in prevention and treatment.
• pneumonia diagnosis often involves imaging and sputum culture.
• Tuberculosis requires a combination of antibiotics for an extended duration.

Conclusion

Respiratory infections encompass a wide range of conditions affecting the upper and lower respiratory tract. Understanding the etiology, clinical presentation, diagnostic approaches, and management strategies for these infections is essential for medical professionals preparing for the USMLE. This guide provides a concise overview of important respiratory infections to help candidates reinforce their knowledge and perform well in the examination.