Rhinoviruses cause the majority of common colds, accounting for 25 to 80 percent of all cases. But they’re far from the only culprit. At least 200 distinct viruses from eight different viral families can trigger what we recognize as “a cold,” which is why you can catch one year after year without ever building lasting immunity.
Rhinovirus: The Leading Cause
Rhinoviruses are a large family of over 100 individual types, split into three species: A, B, and C. Each type is different enough that your immune system treats it as a new infection, which is why catching one rhinovirus cold doesn’t protect you from the next. Rhinovirus A tends to be more common in adults, while Rhinovirus C shows up more frequently in children and may cause more severe symptoms in that age group, including infections that spread deeper into the lower airways. Rhinovirus B generally causes the mildest illness of the three, replicating more slowly and triggering less inflammation in the airway lining.
These viruses work by latching onto specific proteins on the surface of cells in your nose and throat. The majority of rhinovirus types (89 of them) use a protein called ICAM-1 as their entry point. A smaller group uses a different receptor related to cholesterol processing, and the more recently discovered C species uses yet another protein found on airway cells. Once attached, the virus is pulled inside the cell through a normal recycling process, where it releases its genetic material and hijacks the cell’s machinery to produce copies of itself. This is why a cold hits the nose and throat first: those cells have the receptors the virus needs.
Other Viruses That Cause Colds
Coronaviruses (not just the one behind COVID-19, but a broader family of seasonal strains) cause 10 to 20 percent of common colds. Influenza viruses account for another 10 to 15 percent of cold-like illnesses, though these infections can also escalate into something more serious. Adenoviruses contribute roughly 5 percent of cases.
Human parainfluenza viruses are another frequent source of mild, cold-like symptoms: runny nose, cough, sneezing, sore throat, and sometimes fever. In healthy adults, parainfluenza typically stays in the upper airways and resolves on its own. In young children, however, it can cause croup (a distinctive barking cough with noisy breathing), bronchiolitis, or pneumonia. Older adults and people with weakened immune systems are also at higher risk for complications from parainfluenza.
Respiratory syncytial virus (RSV) and certain enteroviruses round out the list. In practice, you’ll rarely know which specific virus gave you a cold because testing isn’t routine for mild respiratory illness, and the treatment approach is the same regardless of the cause.
Why So Many Different Viruses Feel the Same
The stuffy nose, sore throat, and general misery of a cold aren’t caused directly by the virus itself. They’re caused by your immune system’s response. When any of these viruses infects the cells lining your nose and throat, your body releases inflammatory chemicals to fight the invasion. Those chemicals increase mucus production, swell nasal tissue, and trigger sneezing and coughing to expel the virus. Because these immune responses are broadly similar regardless of which virus triggered them, a rhinovirus cold and a coronavirus cold feel essentially identical from the outside.
How Colds Spread and How Long They Last
Cold viruses typically spread through respiratory droplets (from coughs, sneezes, or close conversation) and through hand-to-surface-to-face contact. The incubation period is short: symptoms can appear as early as 12 hours after exposure, though it more commonly takes one to three days.
You’re contagious before you even know you’re sick, potentially spreading the virus a day or two before symptoms show up. The most contagious window is the first three days after symptoms begin, when viral shedding peaks. Total contagiousness can stretch up to two weeks, which is why colds move so efficiently through households and workplaces. Most cold symptoms resolve within 7 to 10 days, though a lingering cough can hang on longer.
Seasonal Patterns by Virus Type
Cold and flu season runs from roughly October through March, but different viruses peak at different times. Rhinoviruses surge in early fall and again in spring, tied to school reopenings and shifts in humidity. Coronaviruses, RSV, and influenza tend to peak in the colder winter months. You can catch a cold any time of year, but infections cluster during these windows because cold, dry air helps viruses survive longer outside the body and because people spend more time indoors in close contact.
When a Cold Becomes Something Else
A standard cold improves steadily after the first few days. If your symptoms persist beyond 10 days without improvement, or if they seem to get better and then suddenly worsen, that pattern suggests a secondary bacterial sinus infection may have developed on top of the original viral cold. Increased facial pain and pressure, thickening or discolored nasal discharge, and a return of fever after initial improvement are the signals worth paying attention to. Bacterial sinusitis, unlike a viral cold, may benefit from antibiotics.
Do Zinc or Vitamin C Help?
Zinc lozenges are one of the most commonly recommended cold remedies, but the evidence remains inconclusive. A meta-analysis of randomized trials found no clear reduction in cold duration with zinc supplementation, with results that could have been due to chance. Individual studies have shown mixed results, and the lack of consistent findings across trials makes it hard to recommend zinc with confidence. Vitamin C has a similar story: regular supplementation may slightly reduce how long a cold lasts (on the order of hours, not days) but does not prevent colds in the general population. Neither supplement is harmful at typical doses, but neither is a reliable fix.