Why do we all catch the cold and flu in winter?

Why do we all catch the cold and flu in winter?

The drop in temperature significantly reduced the innate immune response in the nose, decreasing not only the quantity of extracellular vesicles (EVs) that swarmed the virus but their quality and strength.

This reduced response makes the virus stick to and then infect the nasal cells, where they can then divide and cause the infection…. These findings offer one of the first true mechanistic, biological explanations of why people are more likely to catch colds and other viruses that cause upper respiratory infections in cooler weather.” 

The study, which has been published in the Journal of Allergy and Clinical Immunology.

The mucosa doesn’t lose any of its protective ability in high heat.

Why there are frequent cold and flu in winter?

The flu really does thrive in winter. As it turns out, the virus is basically designed to jump from person to person when the air is cold and dry. Studies have shown that transmission rates are highest when temperature and humidity are both low. Because cold air naturally holds less water, low humidity comes part and parcel with wintertime.

About Extracellular vesicles (EVs)

Extracellular vesicles (EVs)
A 3D image of Extracellular Vesicles

Extracellular vesicles (EVs) are nothing but tiny membrane-bound particles that can carry DNA, RNA and proteins that are released by cells to trigger an antiviral response. 

In the nose, these sacs can prevent viruses from binding to uninfected cells. If they themselves are weakened by cold ambient temperatures, then the virus stubbornly gets stuck to the mucosa.

This is the first, definitive, data-driven evidence of how the body reacts to the virus in winter.

The nose pretty much becomes the gateway for the virus. It also tells us how the nasal cavity, due to its proximity to the cold air outside, is more sensitive and loses its immunity faster than any other organ in the body.

Precautions and Prevention:

Common Cold and Flu in Winter: Prevention and Precautions
Prevention and Precautions

We are just as prone to allergens and extreme weather conditions.

These are not infections but have common symptoms like nose blocks and watering of eyes. That’s why it is better to mask up when going outdoors and inhale steam regularly to decongest your airways.

Build up your immunity with a healthy diet rich in antioxidants, vitamins and proteins, all of which are required for immune cells.

Up your quotient of seasonal fruits and vegetables.

Exercise and build a sleep discipline allowing your body to heal and fight back.

If you follow these simple basic rules, you do not need vitamin C supplements.

The Research

The researchers examined the impact of cold ambient temperatures on the antiviral immune response in the nasal cavity. They first used endoscopy to assess changes in temperature inside the nasal cavity of healthy individuals in response to cold temperatures typically observed during winter.

A drop in the ambient temperature from 23.3 degrees celsius to 4.4 degrees celsius was associated with a decline in temperature inside the nasal cavity by about five degrees celsius.

The researchers simulated this 5-degree celsius drop in intranasal temperatures in the laboratory by culturing human nasal mucosal cells at 32 degrees Celsius instead of 37 degrees Celsius. Lowering the temperature reduced the release of EVs.

Research from the National Institutes of Health suggests that vitamin D plays a role in making an antimicrobial molecule that restricts how well the influenza virus can replicate in laboratory studies.

If we stick to this evidence, given that during winters, there is a lower amount of vitamin D intake from sunlight, one could be more prone to virus attack during colder months.

Source: The Indian Express

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