skip-to-content-text

Common Cold: Viral or Bacterial? The True Cause

Common Cold: Viral or Bacterial? The True Cause | UPMC Italy

The common cold is one of the most prevalent infections of the upper respiratory tract. It circulates mainly during autumn and winter, although it can occur at any time of the year.

Understanding its etiology — and what does not cause it — is essential for managing symptoms appropriately and promoting faster recovery.

What Causes the Common Cold?

The common cold is a viral infection affecting the upper respiratory tract (nose, nasal cavities, pharynx, and larynx).

  • Adults typically experience three episodes per year, most frequently between September and May; children are affected even more often.
  • More than 200 viruses are capable of causing a cold.
  • Rhinoviruses are the most common etiological agents.

Transmission occurs primarily through respiratory droplets expelled when an infected individual coughs, sneezes, or speaks. Indirect transmission can also occur via contaminated surfaces, followed by hand-to-face contact (nose, mouth, or eyes).

Important: The common cold is not caused by bacteria. Bacteria do not induce this condition.

Clinical Manifestations of the Common Cold

After viral exposure, symptoms usually peak within 2–3 days. The most frequent include:

  • Cough
  • Sneezing
  • Nasal congestion or rhinorrhea

Additional symptoms may include:

  • Sore throat
  • Headache
  • Mild myalgia
  • Low-grade fever

Symptomatic Management

In most cases, the common cold resolves spontaneously within approximately 7 days. In children, elderly individuals, or patients with comorbidities, duration may be slightly longer.

Symptom relief can be achieved with over-the-counter medications — such as analgesics, antipyretics, or cough suppressants — always under medical or pharmaceutical guidance.

Supportive measures include:

  • Adequate hydration
  • Rest and sufficient sleep
  • Humidified environment or steam inhalation (hot shower or bowl of hot water)
  • Lozenges or throat pastilles for sore throat and cough
  • Honey to soothe cough (contraindicated under 12 months of age)
  • Saline nasal sprays or drops to relieve congestion
  • Frequent handwashing to reduce transmission

Can the Common Cold Progress to a Bacterial Infection?

Although viral in origin, the common cold may predispose to secondary bacterial infections, particularly when immune defenses are temporarily impaired. The most common bacterial complications include sinusitis, otitis media, and bronchitis; pneumonia is less frequent.

Warning signs of bacterial superinfection include:

  • Persistent or high fever beyond the initial days
  • Severe facial or sinus pain
  • Intense sore throat with painful swallowing
  • Worsening cough or production of thick, yellow-green sputum
  • Dyspnea or labored breathing
  • Chest pain

In such cases, medical evaluation is recommended.

It is also possible to contract streptococcal pharyngitis during a cold. The hallmark symptom is acute sore throat, often without cough. A rapid diagnostic test performed by a physician or pharmacist can confirm the diagnosis.

Cold vs. Influenza: How to Differentiate

Although they share several symptoms, colds and influenza are caused by different viruses and follow distinct clinical courses.

  • The common cold is typically milder and develops gradually.
  • Influenza presents abruptly and is generally more severe.

Influenza is primarily caused by influenza A and B viruses. Typical symptoms include:

  • High fever
  • Chills
  • Musculoskeletal and joint pain
  • Marked malaise
  • Headache
  • Profound fatigue

Influenza is a seasonal illness, spreading mainly between December and February. Vaccination remains the most effective preventive measure, reducing both infection risk and complications, especially in vulnerable populations.

Why Antibiotics Are Ineffective Against the Common Cold and Other Viral Infections

Colds and many other common respiratory infections are viral in origin. Antibiotics act exclusively against bacterial pathogens. Taking antibiotics for a cold does not accelerate recovery, alleviate symptoms, or provide benefit — and may pose health risks.

Risks of Inappropriate Antibiotic Use

Misuse of antibiotics can lead to antimicrobial resistance, complicating future bacterial infections and necessitating stronger medications.

Other risks include:

  • Clostridioides difficile infection, causing severe diarrhea and colitis, potentially life-threatening
  • Mild adverse effects such as rash or gastrointestinal disturbances
  • Severe allergic reactions, occasionally life-threatening

Severe Cold: When to Seek Medical Attention

Most colds resolve spontaneously within a few days. However, in certain cases, symptoms may worsen or indicate complications.

Medical consultation is advised if you or your child experience:

  • Exacerbation of chronic conditions (e.g., asthma, diabetes, cardiovascular disease)
  • Signs of dehydration (dry mouth, reduced urine output, marked fatigue)
  • Respiratory difficulty or tachypnea
  • Persistent fever lasting more than four days
  • Symptoms that improve but recur or worsen
  • Symptoms persisting beyond 10 days without improvement

These warning signs highlight the need for specialist evaluation to prevent complications and ensure appropriate treatment.

Learn more about the Urgent Care service at UPMC Salvator Mundi International Hospital.