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

Cold and Flu in winter: Causes and Prevention

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.

The cold and flu have a well-established seasonal pattern, with cases peaking during winter. The primary reason behind this phenomenon lies in the behavior of the viruses causing these illnesses. During winter, people tend to spend more time indoors, in closer proximity to each other, creating the perfect environment for viruses to spread.

2. The Role of Low Humidity

Winter air is generally cold and dry, resulting in lower humidity levels. This dry environment can weaken our body’s first line of defense, the mucus in our nasal passages and throat, making it easier for viruses to enter our system.

3. Immune System Challenges

During the colder months, our immune system may experience fluctuations due to various factors like vitamin D deficiency from reduced sun exposure and stress. These factors can compromise our ability to fight off infections effectively.

4. Viral Survival in Cold Temperatures

Research suggests that certain viruses, including the flu virus, can survive and remain infectious for longer periods in colder temperatures. This extended viability contributes to increased transmission rates.

5. Indoor Crowding and Transmission

In winter, people are more likely to gather indoors, whether at home, work, or social events. Crowded spaces facilitate the transmission of viruses from person to person through respiratory droplets.

6. Holiday Travel and International Spread

The holiday season often involves increased travel, which can lead to the introduction and spread of viruses across different regions and even countries.

7. Temperature Fluctuations and Immune Response

The fluctuation between warm indoor environments and cold outdoor temperatures can put stress on the immune system, potentially making us more susceptible to infections.

8. Lack of Sunlight and Vitamin D

Limited exposure to sunlight during winter can lead to lower vitamin D levels, which play a crucial role in supporting the immune system.

9. Winter Diet and Nutrition

During the winter months, people may consume more comfort foods and fewer fresh fruits and vegetables, which can impact their overall immune health.

10. How to Stay Healthy During Winter: Practical Tips
  • Wash Hands Frequently: Regular handwashing is one of the most effective ways to prevent the spread of cold and flu viruses.
  • Boost Your Immune System: Focus on a balanced diet, exercise regularly, and consider taking vitamin supplements if necessary.
  • Get Vaccinated: Annual flu vaccinations can significantly reduce the risk of contracting the flu.
  • Stay Hydrated: Drink plenty of fluids to keep your respiratory system moist and healthy.
  • e) Avoid Close Contact with Sick Individuals: Minimize exposure to those who are already ill.
  • f) Keep Indoor Spaces Well-Ventilated: Proper ventilation can help reduce the concentration of viral particles indoors.
Q: Is it true that cold weather causes the flu?

A: While cold weather alone doesn’t cause the flu, it can create conditions conducive to virus transmission.

Q: Can the flu shot give you the flu?

A: No, the flu shot contains inactive viruses, so it cannot cause the flu. Some individuals may experience mild side effects, but they are not the flu.

Q: Are antibiotics effective against the flu?

A: No, antibiotics are only effective against bacterial infections, not viral infections like the flu.

Q: Can I get the flu from a common cold virus?

A: While both cold and flu are caused by viruses, they are different viruses, so you cannot get the flu from a cold virus.

Q: Should I go to work if I have the flu?

A: It’s best to stay home and rest to avoid spreading the flu to colleagues. Most employers understand the importance of staying home when sick.

Q: Is the flu dangerous for healthy adults?

A: While healthy adults may recover from the flu, it can still cause severe symptoms and lead to complications in some cases.

Source: The Indian Express

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