The common cold is the most common human disease in the world. So, why haven’t we found a cure yet?!

Called human rhinoviruses, these respiratory viruses measure between 15 to 30 nanometers in diameter, making them some of the smallest types of viruses out there. And it’s partly thanks to the viruses’ genetic makeup that they’re so good at replicating.

Human rhinoviruses travel like most other respiratory viruses via nasal secretions, which can be released through sneezing, or through contact with fomites, which are surfaces like a keyboard or a doorknob that can help spread the virus from one person to another. From there, all it takes is for a hand to touch one of the body’s mucous membranes like the eyes, nose, or mouth and bam — the virus has gained entry.

Soon after infection, coughing, sneezing, headaches, a mild fever and body aches can soon follow. And these symptoms may easily be confused with those of the flu. But unlike the flu, where symptoms start quite suddenly, it can take a couple of days for cold symptoms to fully develop. And they usually last anywhere from 7 to 14 days.