Pulmonology focuses on diagnosing and treating lung and airway conditions such as asthma, COPD, and pneumonia, as well as overall respiratory health.

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Common Cold: Overview and Definition

The common cold, also known as acute viral nasopharyngitis, is a viral infection that affects the upper respiratory tract. It is the most common infectious disease worldwide, impacting people of all ages. Although it is usually seen as a minor inconvenience, the common cold adds up to a large impact on health and productivity. It mainly affects the nose and throat, but can also cause inflammation in the sinuses, voice box, and windpipe. Many different viruses can cause a cold, not just one. When these viruses invade the lining of the upper airway, the body’s immune system reacts, and this reaction causes most of the symptoms people feel. Chemicals released by the body, such as kinins, prostaglandins, and histamines, lead to swelling, fluid leakage, and increased mucus. At Liv Hospital, we focus on telling the difference between a common cold and more serious illnesses, and we guide patients on how to manage symptoms and avoid complications.

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The Viral Etiology

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There are many different viruses that can cause the common cold, which is why creating a single vaccine is nearly impossible. Rhinoviruses are the main cause, especially in spring and fall. These viruses grow best in the cooler temperatures found in the nose.

  • Rhinoviruses: These are the most common cause, with over 100 serotypes identified. They bind to intercellular adhesion molecule-1 receptors on respiratory epithelial cells.
  • Coronaviruses: Seasonal strains of this virus family account for a substantial percentage of adult colds, typically presenting with symptoms similar to, but sometimes milder than, those of rhinoviruses.
  • Adenoviruses: These pathogens are often associated with more severe symptoms, including conjunctivitis and fever, and can affect the lower respiratory tract.
  • Respiratory Syncytial Virus: While it often causes severe bronchiolitis in infants, this virus typically presents as a typical cold in healthy adults.
  • Parainfluenza Viruses: These are common causes of lower respiratory infections in children but usually result in mild upper respiratory symptoms in adults.
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Transmission Dynamics

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Knowing how the common cold spreads is key to preventing it. The virus mainly spreads in three ways: direct contact, touching contaminated objects, and breathing in droplets from coughs or sneezes.

  • Direct Contact: Physical contact with an infected individual, such as shaking hands, allows the virus to transfer to the recipient’s skin. Subsequent contact with the eyes or nose can lead to viral inoculation.
  • Fomite Transmission: Cold viruses can survive on inanimate surfaces like doorknobs, toys, and phones for several hours. Touching these contaminated objects facilitates transmission.
  • Aerosolization: When an infected person coughs or sneezes, they release microscopic droplets containing the virus. Inhaling these droplets can lead to infection, although this route is considered less efficient than contact transmission for rhinoviruses.
  • Viral Shedding: Infected individuals are most contagious during the first two to three days of symptoms when the viral load in nasal secretions is at its peak.

Pathophysiology of Infection

A cold starts when the virus gets past the nose’s natural defenses. The virus attaches to cells in the nose and begins to multiply. This doesn’t always kill the cells, but it changes how they work and activates the body’s immune system. The immune response brings white blood cells to the area and releases chemicals that make blood vessels in the nose swell and leak fluid. This causes the typical swelling, stuffy nose, and runny nose. The chemicals also irritate nerves, leading to sneezing and a sore throat. These reactions explain the main symptoms of a common cold.

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Seasonal Epidemiology

In places with changing seasons, colds are more common from late summer through winter and less common in spring. This happens because people spend more time indoors and close together during cold weather, making it easier for viruses to spread. Dry air in winter can also dry out the nose, making it harder to block viruses. When school starts, children often catch and spread colds to others. In tropical areas, colds may be more common during the rainy season. Knowing these patterns helps doctors prepare for more cases at certain times of the year.

The Role of the Immune System

The immune system both fights the cold virus and causes the symptoms you feel. The first response acts quickly but is not specific to any one virus. It helps stop the virus from spreading further. Later, the body makes antibodies that target the exact virus, but because there are so many different cold viruses, this protection only works for that one type. Also, immunity to cold viruses does not last as long as it does for some other diseases, so people can get colds many times in their lives.

Global Impact and Burden

Although the common cold is almost never deadly, it causes a big impact on society and the economy. It is the main reason people visit the doctor for sudden illnesses and miss work or school. The costs of doctor visits and medicines add up, but the loss of work time and the need for care are even greater. Even a small decrease in how long or how bad colds are could save a lot of money. Also, people sometimes get antibiotics for colds, which does not help and can make antibiotic resistance worse. Teaching people that colds are caused by viruses is very important for public health.

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FREQUENTLY ASKED QUESTIONS

What exactly defines a common cold?

The common cold is a viral infection of the upper respiratory tract, specifically the nose and throat, caused by one of many different viruses, most commonly rhinoviruses.

No, while they share some symptoms, the flu is caused by the influenza virus and typically presents with more severe symptoms, such as high fever, body aches, and fatigue, whereas a cold is milder.

There is no single cure because the cold is caused by hundreds of different viruses that constantly mutate, making it impossible to create a single medication or vaccine that targets them all.

A typical cold lasts between seven and ten days, though some symptoms, particularly a cough, can linger for up to two weeks or more in some individuals.

Cold weather itself does not cause a cold; a virus does. However, cold weather keeps people indoors and may dry out nasal passages, making transmission easier.

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