Cold and Flu

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The reason why you are ailed by colds again and again is because the virus mutates each time, and your immune system fails to recognize it when you catch your next cold. Usually, the symptoms you experience is your immune system reacting to the virus, and not directly caused by the virus itself. 


Cold or flu?

Many of the symptoms of cold and flu are similar, and that makes them hard to differentiate. There are many viruses that cause the common cold, and the influenza virus is caused by three virus subtypes. Generally, the symptoms of a cold are much milder than those of the flu. 

Common Cold
Frequent sneezing, a mild to moderate fever, low energy and tiredness are all products of the common cold. There are over 100 viruses responsible for the common cold, and it can be acquired at any time of the year. 

Flu
Influenza is caused by virus types A, B and C. Having the flu may induce a moderate to high fever and constant tiredness. It is generally caught in the winter months and can develop into more serious conditions such as pneumonia. 

Shared Symptoms
Both the common cold and flu are classed as upper respiratory tract infections. Either illness may cause a runny nose, sore throat, coughs, headaches, an aching body, shaking and chills. 


How a virus invades a cell

Viruses need to invade healthy cells to replicate. A virus tricks the cell into making copies of it. A cell's nucleus is where instructions to make body proteins are stored. Viruses are surrounded by a coat of protein, and the virus can hijack cells to make these viral proteins. Once they have replicated, the virus will then enter other cells in your body and the cycle continues. This process is the same for both the common cold and the flu. 

  1. The virus attaches itself to your cell and the cell engulfs the virus. 
  2. Substances in the cell begin to strip the virus's outer coat of protein. 
  3. Nucleic acid from the virus is released, ready to be replicated. 
  4. Your cell replicates the viral nuclei acid under the false pretense that it is your own DNA. 
  5. The cell ignores its own chemical needs and switches to making new viral nucleic acids, which become copies of the virus. 

Fever

A rise in body temperature is another way that our immune system combats infection. The body's temperature regulation system is reset to a higher level to speed up immune reactions required to fight infection. As long as a fever is mild, there is no cause for worry - but persistant fevers should be monitored. 



Immune response 

The invasion of viral particles into the epithelial cells found within the mouth or nose triggers an immune response. Symptoms of the common cold or flu are a product of this immune response. The affected epithelial cells release a cocktail of chemicals including histamines which causes an inflammation of your sinuses, and cytokines which command cells involved in your immune response. 

  • Headaches - It is thought the chemical cocktail released during an immune response increases pain sensitivity in the brain, causing headaches. 
  • Moodiness - A change in your mood can be brought about by the annoyance of having a runny nose and lack of sleep. 
  • Sinuses - A dilation of blood vessels in the nasal passages, sinuses, and mucus build up leads to a congested feeling in the head. 
  • Runny nose - The inflammation of your sinuses stimulates mucus production in your nasal cavity. The increased mucus forms a barrier against incoming viral cells. 
  • Sneezing - The release of histamines triggers sneezing, which helps to clear the viral cells out of your nose. However, this also leads to the virus spreading. 
  • Sore Throat - An inflammation of the epithelial cells in the throat is one of the first symptoms of cold and flu, and so is often understood as a warning sign for when you are "coming down" with something. 
  • Coughing - A reflex to clear your airways of mucus build up, coughing may be triggered by inflamed cells of some of the chemicals released as part of the immune response. 
  • Exhaustion - All of these symptoms will interrupt your sleeping pattern. Cytokines exacerbate the feeling of exhaustion, forcing your body to slow down o fight the virus. 
  • Chills - Shivering raises your body temperature - rapid contractions from your muscles generates heat, helping to speed up immune reactions that fight off the infection. 

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