The common cold – what is it?

What happens in the body when you have a cold or flu-like infection?

Germs – especially cold-causing viruses – are extremely versatile microorganisms that are always focused on spreading infection and are constantly evolving and adapting. Their goal is to multiply as freely as possible. It is precisely to protect the body from this that we have the immune system - a complex network of different cells, organs and messenger substances.

Intelligent, interconnected, highly effective:

The human immune system

As soon as foreign invaders enter the body, the body starts to fight them. This is where the immune system comes in.

Travelling through the bloodstream, its "scouts and foot soldiers" ensure that viruses and any bacteria that may have also entered the fray are rooted out.

Antibodies are produced. Made by special immune cells, these attach to germs to form what are known as virus-antibody complexes. These render the invaders immobile, stopping them from entering any more cells and preventing viral multiplication. The viruses are also marked for destruction by other immune cells.

The immune system sends scavenger cells into the affected tissue. There, they hunt down marked viruses – known as "antigen-antibody complexes". Any bacteria or other invaders present suffer the same fate. Scavenger cells surround and destroy antigen-antibody complexes.

Organs of the immune system

Scavenger cells

An appetite for foreign invaders::

Scavenger cells are the foot soldiers of the immune system

What would happen if strangers broke into your home and tried to make themselves comfortable? You'd call the police and have them kicked out.

The immune system works in a similar way. It sends scavenger cells into the affected tissue. There, they hunt down marked viruses – known as "virus-antibody complexes". Any bacteria that may be present suffer the same fate. Scavenger cells "engulf" and destroy virus-antibody complexes.

Fighting off invaders:

Why the immune system needs antibodies

Once inside the body, cold viruses try to continue multiplying. In order to do this, they need to get inside cells.

Made by special immune cells, antibodies attach to germs to form what are known as virus-antibody complexes. These are then no longer able to enter any more cells and viruses are prevented from multiplying.

The complexes themselves are consumed and destroyed by the scavenger cells. Antibodies also attach to bacteria, preventing them from dividing further.

Invisible, aggressive, geared up to multiply:

The tactics of cold viruses

Every winter, a multitude of viruses are on the move, out to infect us. Invisible even under the microscope, they spread with a snowball effect and try to find as many victims as possible.

Normally, we are protected against the tiny invaders by strong barriers – skin and mucous membranes. But if the mucous membranes in the nose and bronchi have been made weak and permeable by too much dry indoor heating air, this opens the door to cough, cold and flu viruses.

Once they have entered the body, the cold viruses then start to spread like wildfire. The cold takes hold.

The 3 levels of defence

When cold viruses break through the mucous membrane barrier, that's when colds take hold

It starts with a sore throat:

How to tell that you've caught a cold

When viruses enter the body via the mucous membranes, they go undetected. It's not until they have multiplied in the body that you notice the first symptoms.

Colds typically start in the throat. At the point where the air enters the throat from the nose, difficulty swallowing tells you that a cold is on its way. In this early phase, you may also feel slightly unwell.

A runny nose, cough or aching limbs sometimes don't develop until as much as a day later, however.

Cough, fever, aching limbs:

How a cold feels

Colds, bronchitis and flu-like infections are viral respiratory illnesses that can have different patterns of symptoms depending on the type of germs involved.

Symptoms of infection: The typical course of a cold