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Common Colds for the ABIM

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Common colds for the American Board of Internal Medicine Exam
Pathophysiology
  • Viral Infection:
    • The common cold is caused primarily by viral infections of the upper respiratory tract. Rhinoviruses are responsible for about 50% of cases, followed by coronaviruses, adenoviruses, enteroviruses, and respiratory syncytial virus (RSV).
    • Rhinoviruses enter the nasal epithelium by binding to intercellular adhesion molecule-1 (ICAM-1) receptors, initiating infection and an inflammatory cascade. Inflammation of the nasal and pharyngeal mucosa leads to typical cold symptoms.
Respiratory viral infection
  • Immune Response:
    • Viral replication triggers the release of cytokines (e.g., interleukins, interferon) from infected epithelial cells, leading to vasodilation, increased vascular permeability, and mucus production. These immune responses cause nasal congestion, rhinorrhea, and pharyngitis.
  • Transmission:
    • The common cold is highly contagious, primarily spread by:
    • Direct contact: Viral particles are transferred via contaminated hands or objects.
    • Aerosolized droplets: Viruses are spread through respiratory droplets when an infected person coughs or sneezes.
Clinical Features
  • Incubation Period:
    • The incubation period for the common cold is typically 1-3 days following viral exposure.
  • Nasal Congestion and Rhinorrhea:
    • Nasal congestion and discharge are hallmark symptoms. Rhinorrhea starts watery but may become thicker and yellow or green as the infection progresses.
  • Sore Throat:
    • Pharyngitis or throat discomfort is common in the early stages of the infection.
  • Cough:
    • A dry cough is frequently associated with a cold, often worsening in the later stages as postnasal drip increases.
  • Sneezing:
    • Triggered by irritation of the nasal mucosa, sneezing is a frequent early symptom.
  • Malaise and Fatigue:
    • Generalized fatigue and a sense of illness are often present but are typically mild compared to influenza.
  • Fever:
    • Fever is uncommon in adults with colds, but low-grade fever may occur, especially in children.
  • Headache and Myalgias:
    • Mild headache and muscle aches may occur but are less pronounced than in influenza.
  • Duration:
    • Symptoms generally last 7-10 days, though cough can persist for up to 2 weeks.
Diagnosis
  • Clinical Diagnosis:
    • The diagnosis of a common cold is typically based on the clinical presentation. The history of gradual onset, mild fever (if present), nasal symptoms, and absence of severe systemic symptoms (e.g., high fever, myalgias) differentiates it from influenza.
  • Differential Diagnosis:
    • The common cold must be differentiated from other upper respiratory tract infections, such as:
    • Influenza: More severe systemic symptoms (e.g., high fever, body aches) and abrupt onset.
    • Acute Bacterial Sinusitis: Prolonged nasal congestion (>10 days), facial pain, and purulent nasal discharge suggest a bacterial infection.
    • Allergic Rhinitis: Seasonal or perennial symptoms, sneezing, itchy eyes, and clear nasal discharge without fever or systemic illness.
    • COVID-19: While similar in early symptoms, COVID-19 may present with fever, cough, shortness of breath, and anosmia. Testing is essential for differentiation during the pandemic.
  • Laboratory Testing:
    • Routine viral testing or cultures are generally unnecessary for diagnosing the common cold. However, during outbreaks (e.g., COVID-19), PCR testing for specific respiratory viruses may be used to rule out other causes.
Management
Symptomatic Treatment
  • Nasal Decongestants:
    • Intranasal decongestants (e.g., oxymetazoline) reduce nasal congestion by causing vasoconstriction. Limit use to 3-5 days to avoid rebound congestion (rhinitis medicamentosa).
    • Oral decongestants (e.g., pseudoephedrine) are also effective but may cause systemic side effects such as hypertension, insomnia, and tachycardia.
  • Antihistamines:
    • First-generation antihistamines (e.g., diphenhydramine) may help alleviate rhinorrhea and sneezing by reducing histamine-mediated mucus production. However, they can cause drowsiness and dry mouth.
  • Intranasal Corticosteroids:
    • These are not typically recommended for the common cold, as their benefit is minimal for short-term viral infections.
  • Analgesics and Antipyretics:
    • Acetaminophen and ibuprofen can reduce fever, headache, and body aches. Aspirin should be avoided in children due to the risk of Reye syndrome.
  • Cough Suppressants and Expectorants:
    • Dextromethorphan is commonly used for cough suppression. Guaifenesin may help with mucus expectoration but has limited efficacy in colds.
Supportive Care
  • Hydration:
    • Maintaining good hydration helps thin mucus secretions, promoting drainage and reducing congestion.
  • Rest:
    • Adequate rest supports immune function and may shorten the duration of illness.
  • Humidification:
    • Using a humidifier or vaporizer can relieve nasal congestion and throat irritation by keeping mucous membranes moist.
  • Saline Nasal Sprays:
    • These sprays help loosen mucus and relieve nasal congestion without the risk of medication side effects.
Antibiotics
  • Not Recommended:
    • Antibiotics are ineffective against viral infections and should not be prescribed for the common cold. Their overuse increases the risk of antimicrobial resistance.
Prevention
  • Hand Hygiene:
    • Regular handwashing with soap and water, or using alcohol-based hand sanitizers, is one of the most effective ways to prevent the spread of cold viruses.
  • Avoid Close Contact:
    • Avoiding close contact with infected individuals and practicing good respiratory hygiene (e.g., covering coughs and sneezes) can reduce transmission.
  • Vaccine:
    • Currently, there is no vaccine available for the common cold due to the large number of viral strains responsible for the illness. However, vaccines for specific respiratory viruses (e.g., influenza, COVID-19) can reduce overall respiratory infection burden.
Complications
  • Secondary Bacterial Infections:
    • Although rare, some patients may develop secondary bacterial infections such as acute bacterial sinusitis or otitis media. These complications typically present with worsening symptoms after initial improvement.
  • Asthma Exacerbations:
    • Viral upper respiratory infections can trigger asthma exacerbations, leading to increased wheezing, coughing, and difficulty breathing.
  • Chronic Bronchitis Exacerbation:
    • Patients with chronic obstructive pulmonary disease (COPD) may experience exacerbations triggered by viral infections.
Key Points
  • The common cold is a viral upper respiratory infection most often caused by rhinoviruses. Other etiologies include coronaviruses, adenoviruses, and respiratory syncytial virus (RSV).
  • Typical symptoms include nasal congestion, rhinorrhea, sore throat, cough, sneezing, and malaise. Fever is uncommon in adults but may occur in children.
  • Diagnosis is clinical, with no need for routine viral testing. The common cold should be differentiated from other causes of upper respiratory tract infections, such as influenza, acute bacterial sinusitis, and COVID-19.
  • Treatment is supportive and focuses on symptom relief through nasal decongestants, antihistamines, analgesics, and hydration. Antibiotics are not indicated.
  • Complications are rare but include secondary bacterial infections and exacerbations of underlying conditions like asthma or COPD.

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