As winter arrives, so does the familiar wave of coughs and colds. It’s not just your imagination; there are clear biological and environmental reasons why respiratory illnesses like the flu, RSV, and COVID-19 thrive in colder months.
It’s Not Just the Cold, It’s the Air
For years, the common
thinking was that we get sick more in winter simply because we are crowded together indoors. While that is a major factor, researchers have uncovered a direct biological reason: cold air impairs our body's primary line of defence. Our noses have a remarkable, previously unknown immune response that attacks viruses upon entry. However, a drop in temperature can significantly weaken this defence. Studies have shown that when healthy individuals are exposed to cold air, the temperature inside their nose drops, which in turn reduces the effectiveness of this immune response by nearly 42 percent. This makes it much easier for viruses to take hold and cause an infection.
The Double Threat of Dryness
Winter air isn't just cold; it's also notoriously dry. This low humidity creates a perfect storm for viruses in two ways. First, it helps viral particles survive and linger in the air for longer periods, increasing the chances of inhalation. When an infected person coughs or sneezes, the droplets they expel lose moisture and become smaller, lighter aerosols that can travel farther in a poorly ventilated room. Second, dry air dehydrates the protective mucous membranes in our nose and throat. This can cause irritation, slow down the natural clearing process of our airways, and weaken this critical physical barrier, making us more susceptible to any virus we encounter.
The Indoor Gathering Dilemma
The behavioural shift during winter is undeniable. We spend more time inside our homes, offices, and public spaces to escape the cold. This proximity to others naturally increases the opportunities for viruses to spread from person to person. Indoor environments, especially those that are crowded or have poor ventilation, allow a build-up of airborne virus particles. Holiday gatherings, while a source of joy, are high-risk situations for transmission. Singing, talking, and simply breathing can expel viral particles into a shared space, where they can easily infect others.
Finding the Humidity 'Sweet Spot'
While dry air is problematic, there appears to be an optimal humidity level for indoor spaces. Research from MIT suggests that maintaining an indoor relative humidity between 40 and 60 percent is associated with lower rates of respiratory infections. In this range, airborne viruses are inactivated more quickly, and our respiratory system's defences function more effectively. Below 40% humidity, viruses can thrive. Using a humidifier during winter can be a simple but powerful tool to add moisture to the air, helping to create a less hospitable environment for viruses and supporting your body's natural defences.
Simple Steps for a Healthier Winter
Protecting yourself involves a multi-layered approach. Staying up-to date on vaccinations for the flu, COVID‐19, and RSV is a critical first line of defence. Simple hygiene practices remain essential: wash your hands frequently with soap and water, cover coughs and sneezes, and avoid touching your face. Improve indoor air quality by opening windows to increase ventilation, even for a few minutes a day, or by using air purifiers. When you go outside, wearing a scarf or mask over your nose and mouth can help warm and humidify the air you breathe before it reaches your lungs. If you do feel sick, staying home is the best way to prevent further spread to your community.
