Does it make any amount of sense that an object which can hardly be called a living organism, and which is difficult to see even under standard microscopes, can make human life miserable by inducing a runny nose, chills, fever and sneezing fits that can last for as long as a week? But then, that's life, where most things that take place do not make any rational sense! But they still happen, and in order to resolve the conflict between fact and logic, we always manage to invent an explanation to justify such an irrational occurrence. Ah well, before I get any more philosophical and drift further from the titular subject, let's move towards getting a closer look at the common cold pathogens. What? Did I just catch you telling yourself " Aw, I know... it's virus, of course!"? Well, just read ahead anyway, because there's more to those viruses than you might imagine! What Causes Common Cold? Common cold has less to do with the cold season itself and more to do with the common cold causing viruses, though these viruses do show a penchant for cooler and more temperate climates, when they spread most. You see, during the winters, people tend to spend less time bathing and cleaning than during summers, and those endless layers of warm clothing that doesn't get washed on a daily basis become an ideal breeding ground for disease-causing pathogens. That is the reason why most people seem to catch a cold in cooler weather conditions, such as the latter part of autumn and winter. Anyway, coming back to the subject of common cold pathogens, yes, you were correct in stating that common cold is a viral infection. However, there are two types of viruses that are primarily responsible for inducing common cold symptoms (chills, runny nose, sneezing, sore throat, cough with or without mild fever, etc.) - Rhinoviruses and Coronaviruses. Among these two, rhinoviruses are the most common pathogens that are responsible for cold and related symptoms, accounting for as many as 50% of all common cold cases. Coronaviruses are responsible for 10-15% of all common cold cases, while the responsibility for the remaining 40-45% of the cases are shared by influenza viruses, other enteroviruses, adenoviruses, human parainfluenza viruses, the human respiratory syncytial virus, and the metapneumovirus. All of these viruses share one thing in common - they infect various parts of the respiratory system in humans (sometimes other animals as well), whether or not they have any pathogenic influence on any other organ or part of the body. Brief Overview of Rhinovirus and Coronavirus All said and done, the hunt for the chief culprits that cause common cold boil down to rhinoviruses and coronaviruses. Rhinovirus is a viral species that belongs to the Enterovirus genus of the Picornaviridae family. Rhinoviruses are single stranded, positive sense RNA viruses, that have an icosahedral structure. As far as rhinoviruses that affect humans are concerned, there exist three different species - Human rhinovirus A, Human rhinovirus B, and Human rhinovirus C. This virus is non-enveloped, meaning the viral particles including protein capsids are not covered by any outer material. Coronavirus is a viral species that belongs to the Coronavirinae subfamily of the Coronaviridae family. Contrary to rhinoviruses, coronaviruses are enveloped and have a single stranded positive sense RNA structure. Coronaviruses infect non human mammals as well as birds, besides humans. Both viruses infect the respiratory system, with rhinovirus preferring the upper respiratory tract for latching and propagation, while the coronavirus infects both the upper as well as lower respiratory tract. Usually, the common cold incubation period is about 2 days, with a few instances where the symptoms surface within 20 hours of infection. Antibiotics do not work on common cold, as it is a viral infection. On the other hand, they cause more harm than good, as they weaken the immune system, which opens the doors for many other opportunistic pathogens to invade the body. Common cold remedies usually include such food and medicinal items that fortify and strengthen the immune system, as it is the immune system alone that can fight viruses. That's why vitamin and zinc supplements are recommended for individuals suffering from a common cold, along with nutritious food, lots of fluid, and as much rest as possible.