Scientists have uncovered new insight into why some people develop symptoms after catching a cold virus while others remain unaffected, pointing to a powerful line of defense hidden inside the nose. A study published Monday in the journal Cell Press Blue suggests that the body’s earliest immune response in the nasal passages plays a decisive role in determining whether a rhinovirus infection turns into a full-blown cold.
Rhinoviruses are the most common cause of colds and surge during winter months, yet exposure does not always lead to illness. According to the research, led by Dr. Ellen Foxman of Yale School of Medicine, only about half of people who carry the virus in their noses actually develop symptoms. The difference, scientists found, lies in how nasal cells react in the first hours after exposure.
To investigate, researchers grew nasal tissue in a laboratory, allowing them to closely observe how cells lining the nose and lungs respond at a molecular level when exposed to rhinovirus. This approach offered an unusually detailed view of the earliest stages of infection, revealing two sharply different immune outcomes.
In what researchers describe as a strong or effective response, fewer than one percent of nasal cells become infected. This happens when the body rapidly produces interferons, proteins that block viruses from entering cells and replicating. Interferons also help coordinate a broader antiviral response, stopping the infection before it spreads. When scientists experimentally disrupted this interferon response, the virus was able to multiply more freely, highlighting how critical timing is in preventing illness.
When this early defense fails, the virus spreads through the tissue, infecting as many as 30 percent or more of the cells. This triggers a cascade of inflammatory proteins, increased mucus production and the familiar symptoms of a cold. In this scenario, inflammation rather than viral control dominates the immune response, leaving the person feeling congested, fatigued and unwell.
What determines whether the body mounts a protective or harmful response is still not fully understood. However, the study identified several conditions that appear to tilt the balance. People who have recently fought off another viral infection may retain a heightened interferon response, making it easier for their immune system to quickly shut down a new virus before symptoms emerge.
Environmental factors also play a significant role. Cooler air in the nasal passages and lungs appears to give viruses an advantage by delaying or suppressing interferon production. This finding offers a biological explanation for why colds are more common in colder weather. Exposure to pollution or cigarette smoke was also shown to worsen outcomes by altering immune responses and promoting inflammation rather than viral control.
While the research does not yet translate into specific steps people can take to prevent colds, it provides a clearer picture of the microscopic battle that unfolds inside the nose with every exposure. By showing how early immune responses can determine the course of infection, the findings may eventually guide new strategies to prevent or treat common respiratory illnesses.
