Winter in the United States officially begins this week, and just like in previous years, cases of the common cold and flu are expected to rise during this time of the year.
Previous studies found that respiratory infections spread more readily in the wintertime because people spend more time in enclosed spaces where the air is dry. When a person transmits viruses to other people, they are in the so-called “breathing zone,” which is approximately 3 feet away from one another. And during a time of low humidity such as in winter months, the moisture that surrounds the viruses evaporates, allowing them to remain in the air for a sufficiently prolonged time, and consequently making more people susceptible to viral infections.
While the incidence of common cold and flu during the cold months has been well researched for quite some time now, whether the season’s chilly and damp weather may actually weaken a person’s immune system was less certain until a recent study found a biological explanation why people get more respiratory illnesses in winter.
Why do you get sick in the cold?
According to a study published in The Journal of Allergy and Clinical Immunology on December 6th, 2022, cold air itself damages the body’s immune response occurring in the nose.
“There’s never been a convincing reason why you have this very clear increase in viral infectivity in the cold months,” said Benjamin Bleier, a co-author of the study and a surgeon at Harvard Medical School and Massachusetts Eye and Ear in Boston. “This is the first quantitative and biologically plausible explanation that has been developed.”
Previous research from the team had discovered that when we breathe, cells inside our nose release tiny particles called extracellular vesicles (EVs) that swarm, bind, and kill bacteria and viruses. In their latest study, they found that this immune response in the nose is also triggered by viruses and that lower temperatures affect the strength of EVs.
What are extracellular vesicles?
When respiratory viruses or bacteria invades the nose, cells lining the nose instantly start creating EVs, which are billions of simple copies of themselves. While EVs can’t divide themselves as cells can, Bleiber described EVs as “little mini versions of cells specifically designed to go and kill these viruses,” noting that “EVs act as decoys that when you inhale a virus, the virus sticks to these decoys instead of sticking to the cells.”
Once produced, the billions of EVs start to swarm the marauding germs, just like hornets would swarm you if you attacked their nest.
“It’s like if you kick a hornet’s nest, what happens? You might see a few hornets flying around, but when you kick it, all of them all fly out of the nest to attack before that animal can get into the nest itself,” he said. “That’s the way the body mops up these inhaled viruses so they can never get into the cell in the first place.”
Cells in the nose lining then expel EVs in the form of nasal mucus, stopping invading viruses from actually getting into the body where they are bound to multiply.
According to the study, the nose increases the production of EVs by 160% when under attack.
Original cells vs extracellular vesicles
Compared to the original cells that produced the EVs, the latter had more receptors on their surface than the former. “Just imagine receptors as little arms that are sticking out, trying to grab on to the viral particles as you breathe them in,” Bleier explained. “And we found each vesicle has up to 20 times more receptors on the surface, making them super sticky.”
Cells in the body contain a viral killer called micro RNA. But the study found that EVs in the nose contain 13 times micro RNA sequences than normal cells.
What happened when cold weather hits
To learn how cold weather affects this immune response occurring in the nose, the researchers exposed four study participants to 15 minutes of 40-degree-Fahrenheit (4.4-degree-Celsius) temperatures and then measured conditions inside their nasal cavities.
“What we found is that when you’re exposed to cold air, the temperature in your nose can drop by as much as 9 degrees Fahrenheit. And that’s enough to essentially knock out … those immune advantages that the nose has,” Bleier said.
He pointed out that the said drop in temperature was enough to take nearly 42% of the EVs out of the fight. “Similarly, you have almost half the amount of those killer micro RNA’s inside each vesicle, and you can have up to a 70% drop in the number of receptors on each vesicle, making them much less sticky,” he added.
Bleier and his team of researchers concluded that weakened EVs cut the ability of our immune system to fight off respiratory infections by half.
All these findings could help develop future treatments against the common cold and other viral diseases such as COVID-19. Bleier, in particular, expects to see the development of topical nasal medications build upon the results of their study.
“[These new medicines will] “essentially fool the nose into thinking it has just seen a virus,” he said. “By having that exposure, you’ll have all these extra hornets flying around in your mucous protecting you.”
Can you get a cold from being in the rain?
Some people may have told you that you can catch a cold by getting caught in the rain, but medical experts say this is a myth.
“All our parents used to say that, perhaps to keep us indoors in bad weather,” Stephen Morse, PhD, an epidemiology professor, and an infectious disease expert at Columbia University in New York, told Healthline. “But getting wet and chilled is also associated with colder months, so the correlation was obvious, and people tend to notice the times they got wet and did get sick, not the times they didn’t. But as we say in epidemiology, correlation is not necessarily causation.”
Dr. Jaime Friedman, a San Diego-based pediatrician, added that myths associating wet weather with catching colds possibly evolved due to a poor understanding of viruses.
“I would imagine that before anyone knew about germs, it would make sense that the cold and shiver you feel when you are wet feels similar to the cold and shiver of a fever and an illness, therefore associating one with the other,” Friedman said in an interview Healthline, before pointing out that we can get sick whatever the weather is.
“It also makes sense that since viruses thrive in cold weather, we get sick more often in cold weather,” she said. “[But] we now know that colds are caused by viruses and pneumonia is caused by viruses or bacteria, so you can only get sick if you are exposed to these germs, regardless of the weather.”
What month do people get sick the most?
In the U.S., flu season usually occurs during the fall and winter months. While flu viruses spread all year round, flu activity usually peaks between December and February, according to the country’s Centers for Disease Control and Prevention (CDC).
How do you get rid of winter sickness?
According to MayoClinic.org, below are some remedies that might help you feel better if you have a cold or flu during the winter months or whatever the season is.
- Stay hydrated. Drinking water, juice, clear broth, or warm lemon water with honey help loosen respiratory congestion and prevents dehydration.
- Rest. Your body needs to heal, so it’s important to avoid any kind of physical activity when sick.
- Soothe a sore throat. A saltwater gargle can relieve a sore or scratchy throat.
- Fight stuffiness. Nasal drops and sprays can help relieve stuffiness and congestion.
- Add moisture to the air. Use a cool-mist vaporizer or humidifier to add moisture to your home. This might help loosen congestion.
- Try over-the-counter cold and cough medications. For adults and children aged 5 and older, OTC over-the-counter decongestants, antihistamines, and pain relievers might offer some symptom relief. It’s worth noting, however, that they won’t prevent a cold or shorten its duration, and most have some side effects.