A molecular surface model of Human Rhinovirus-14, one of 99 known rhinoviruses which usually enters through the upper respiratory tract and is the primary cause of the common cold. Measuring about 30 nanometers in diameter, human rhinoviruses are some of the smallest viruses in the world and ideal temperatures in the upper respiratory tract allow it to quickly infect and replicate within the host. These produce symptoms such as soar throat, coughing, sneezing and nasal congestion.