Introduction:
A cold is a viral infection that is quite contagious, meaning it can spread from person to person at a very fast pace. After catching the cold virus from someone, it takes around two to three days for the symptoms to start. This means that even before an individual starts to suffer the symptoms, the virus is active in the body. And chances are, one has already passed it on to someone else at home, work, or school. One may remain contagious as long as the symptoms last. Hence understanding the infectious period (the timespan when an infection can potentially spread from one individual to another) helps take the necessary precautions.
What Are the Different Types of Cold?
Most colds, typically known as the common cold, are caused by rhinoviruses. The flu or influenza virus also causes cold symptoms and upper respiratory tract infections. Coronaviruses are the next in this category. Each of them has a different onset of symptoms and infectious period.
What Is the Timeline of Infection in Cold and Other Upper Airway Infections?
From the moment of catching the virus, till the infection subsides, symptoms of a common cold or upper respiratory tract infection follow a definite sequence of progression. It goes like this:
Stage 1:
Catching The Infection - An individual tends to breathe in the virus through contaminated air or touch a contaminated surface. Droplets produced by a sneeze can travel across the room, though big droplets drop off by six feet. So ideally, being as close to three feet from an infected person puts one at risk of catching a cold. Cold viruses are often spread when infected hands touch the eyes and nose. Viruses can live on doorknobs, light switches, and other general spaces for a few hours. From there, the virus is transferred to the hand through touch and eventually to the mouth or nose.
Stage 2:
Incubation Period - This is the time span between the virus’s entry into the body and the start of symptoms. For the common cold, the incubation period is usually one to three days. Whereas for the seasonal flu, it may be one to four days. The coronavirus may stay in the body for about two to five days before one may notice the early symptoms.
Stage 3:
Onset Of Symptoms - This is when the body starts to respond to the virus inside the upper airway. The immune system reacts by activating macrophages, which are specialized disease-fighting types of white blood cells. These macrophages trigger the release of small proteins called cytokines and bradykinin. Early cold symptoms, such as sore throat and nasal congestion, are triggered by bradykinin. Cytokines cause fever and chills in some people. Let us look at the progression of symptoms here:
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Sore Throat - This is often the first symptom. The pain that one feels is due to the action of hormones (prostaglandins) and proteins (bradykinin) on the sensory nerve endings in one’s upper airway. The pain signals are carried to the brain by the cranial nerves in the area.
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Sneezing - An inflammation of the nerves triggers the trigeminal nerve (fifth cranial nerve) to activate the sneeze center in the brain. The brain then triggers the sneeze reflex (tendency to sneeze).
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Runny Nose - The trigeminal nerve stimulates the glands of the upper airway to release a clear nasal discharge. As the cold continues for several days, the clear discharge may turn slightly yellow to darker yellow with a greenish shade. The color keeps changing as the number of disease-fighting white blood cells in the fluid increases due to progressing inflammation. The color of the nasal discharge can tell how much inflammation is going on in the body.
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Sinus Pain - An inflamed sinus can be very painful. After the nasal congestion starts, there will be an increase in pressure inside the bony spaces of the maxillary sinuses (air-filled bony spaces on either side of the nose). The sinus pain often worsens when one bends or lies down due to pressure changes in the surrounding blood vessels.
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Watery Eyes - There is a small tunnel running from the nose that opens into the inner corner of each eye (nasolacrimal duct). This duct may get blocked due to swelling and congestion of the skin inside the nose. And causes tears to accumulate in the eyes to develop watery eyes.
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Cough - It can last for more than three weeks. Nasal irritation can cause sneezing. But once the inflammation moves down the throat (larynx) and gets closer to the lungs, a cough reflex is triggered. As the inflammation gets passed on to the lower airway, one may cough up yellow or green sputum. Again, the color of the sputum can tell how much inflammation is going on in the body. Unfortunately, the cough can last for several weeks after the other symptoms subside.
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Muscle Aches - Most affected individuals get muscle aches. The inflammatory reactions trigger the release of a hormone called prostaglandin. This hormone triggers muscle pain in the body.
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Fever - Fever is not common with the common cold caused by rhinovirus. It is more likely to occur if one is infected with the influenza virus or others. When one is infected, the cytokines send signals to the hypothalamus, which is the temperature control system in the brain. The body temperature increases, and one may start shivering. This is what one describes as fever and chills.
Stage 4:
Resolving The Symptoms - Symptoms improve gradually, and it may take around seven to ten days to fully recover from the cold. Most people with the common cold do not need to see a doctor, especially if one's body is reacting in the above-mentioned sequence. One may take over-the-counter medicines to relieve the symptoms. Vitamin C and zinc supplements help with fast recovery. Doctors recommend taking proper rest and drinking plenty of fluids to ease the symptoms. However, if an individual starts to experience more severe symptoms, such as a fever lasting for more than a day or two, one may need to see the doctor.
How Long Is the Cold Contagious?
With a cold virus, people tend to stay contagious for about a day ahead of symptoms and remain that way for a few more days. One starts to become contagious the day before noticing the symptoms and continues to shed the virus for about ten days after feeling sick. According to the existing guidelines, one may avoid contact with other people until the fever is gone and wait for another twenty-four hours to start interacting with others.
The influenza virus is most contagious in the first twenty-four hours. It can spread from the day before the onset of symptoms and continue to be contagious for about a week. Children may stay contagious for up to four days before the start of symptoms which is why it is spread fast among children. Ideally, it is recommended to stay home until one stops coughing and not running a fever anymore.
Conclusion:
Common cold has no cure so far. One has to wait for the body’s immune system to fight the infection, which typically takes seven to ten days. An influenza vaccine may decrease the chance of getting the flu, which may have more severe symptoms than the common cold. Coronavirus vaccines also help prevent or keep the symptoms minimal in an affected individual. Doctors highly recommend scheduled vaccinations to prevent such colds.
