Viruses as a cause

Over 90% of all colds are caused by viruses. The triggering viruses can come from a wide variety of families, such as the rhinoviruses, coronaviruses or the RS virus (respiratory syncytial virus). Within these families there is a large number of different subtypes of these viruses.

This explains why humans can fall ill with a viral cold again and again. The immune system can very effectively fight those viruses that it has already encountered. However, if a new subtype of a virus attacks humans, the immune system needs longer to recognize the pathogen as such and to fight it effectively.Due to this time delay, symptoms can develop, which are colloquially called cold symptoms.

A distinction must be made between these and influenza viruses, which are the pathogens of seasonal influenza. These cold viruses are adapted to bypass the natural protective barrier of the nasal and pharyngeal mucosa. That is why they trigger similar symptoms, although they come from different families.

The respiratory syncytial virus, also known as RS virus, is a common trigger of a cold and inflammation of the lower respiratory tract (bronchiolitis) in children. RSV infection is even the most common disease in infancy and childhood. In adulthood, the RS virus plays a rather minor role.

The RS virus is very resistant to environmental influences and is transmitted via tiny droplets in the air we breathe. The triggered infection is characterized by high fever and respiratory distress. Affected children often have to be treated in hospital.

Corona viruses are crown-shaped viruses when viewed under the microscope, from where their name is derived. In most cases, they cause a comparatively mild infection of the respiratory tract. Like all other cold viruses, the corona virus infects the nasal mucosa.

Through a special mechanism, the virus paralyzes the defense function of the mucous membrane so that cold symptoms, such as a cold or cough, can occur. However, a certain type of the virus can trigger a so-called SARS (Severe acute respiratory syndrome). SARS was first observed in 2002. The patients show pneumonia, which can lead to lung failure in the further course of the disease.