Causes of a cold

Causes and forms of a cold

The symptoms of coughing with increased sputum, sore throat, headache and body aches and runny nose can appear both individually and together, which would then lead to the full picture of the common cold. In the vast majority of cases, a cold is always part of the common cold. Depending on the duration of the cold and the amount of nasal secretions produced, the paranasal sinuses may also be involved (sinusitis), which would be noticeable in the form of moderate to severe headaches and painful knocking over the corresponding sinuses.

Most common cold-causing factors are viruses. Furthermore, it can happen that a bacterial infection follows after the disease has broken out (bacterial superinfection or secondary infection), which must then be treated with antibiotics. So far, around 220 different viruses have been identified that can cause a cold. The corresponding viruses are assigned to virus families, which in turn contain numerous subtypes of viruses. The following virus groups have been identified as causing colds: to the family of Coronaviridae belong that Coronavirus with some subtypes, to the family of Picornaviridae count the human rhinovirus with more than 100 subgroups, Coxsackie viruses, Echo viruses and human enteroviruses. To the virus family of Paramyxoviridae one counts them human parainfluenza viruses with some subtypes, the human metapneumovirus and the human respiratory syncytial virus (HRSV). The group of adenoviruses includes human adenoviruses with some subgroups and that Mastadenovirus. Furthermore, different subtypes of the Reoviridae virus family can cause a cold. The most common rhinoviruses cause a cold (40% of the time), followed by the coronaviruses (10% -25%) and the HRSV (10-15%).

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Metapneumovirus mainly causes cold symptoms in young children. When it comes to viruses, one differentiates between enveloped and non-enveloped virus forms. While the non-enveloped viruses can usually be recognized and fought by the immune system, the enveloped viruses are able to bypass the immune system and lead to longer and more pronounced courses of the disease. Furthermore, enveloped virus forms are able to mutate earlier and more quickly, i.e. change the protein composition of the outer layer in such a way that the immune system cannot adapt to them. The constant change in the structure of the virus and the variability associated with it explains why cold infections can occur so frequently in humans.

Viruses can survive particularly well in a moist environment, which explains why most colds occur between September and November. Contrary to popular and persistent opinion, cold and wet weather alone cannot cause a cold in humans. Numerous studies and investigations by the US Navy have shown that there is no connection between exposure to cold and moisture and the development of a cold. The Navy let numerous swimmers swim in very cool water for a certain time in the open sea, then recovered them and examined the swimmers for the presence of cold symptoms. There was no significant increase in the incidence of colds. The reason is the necessary presence of pathogens in order to be able to trigger a cold. Cold and wet alone are not enough. However, recent studies have found that the two factors cold and wet can have a secondary influence on the risk of illness. In order to fight off an infection, a person absolutely needs a well-functioning immune system. The investigation found that this does not work properly in a very cool environment and thus represents a possible entry point for the pathogens.

Read more on the topic: Preventing a cold

Viruses as the cause

Viruses cause over 90% of all colds. 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 are again a large number of different subtypes of these viruses. This explains why people can catch a viral cold again and again.

The immune system can very effectively fight those viruses it has encountered before. However, if a new subtype of a virus attacks humans, the immune system takes 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.

The influenza viruses, which cause seasonal flu, must be distinguished from this. These cold viruses are adapted to bypass the natural protective barrier of the nasal and pharyngeal mucosa. Therefore, they also trigger similar symptoms, even though they come from different families.

RS viruses

The respiratory syncytial virus, also called RS virus, is a common cause of the common cold and inflammation of the lower respiratory tract (Bronchiolitis) in childhood. The RSV infection is even the most common disease in infancy and childhood. The RS virus plays a subordinate role in adulthood.

The RS virus is very environmentally resistant and is transmitted via the smallest droplets in the air we breathe. The infection caused is characterized by a high fever and shortness of breath. Affected children often have to be hospitalized.

Corona viruses

Corona viruses are crown-shaped viruses when viewed under a microscope, from which their name is derived. In the most common cases they cause a comparatively mild infection of the respiratory tract. Like all other cold viruses, the corona virus attacks the nasal mucosa. Using a special mechanism, the virus paralyzes the defense function of the mucous membrane, so that symptoms of the common cold, such as a runny nose or cough, can occur.

However, a certain genus of the virus can be called SARS (Severe acute respiratory syndrome) trigger. The SARS was first observed in 2002. The patients show pneumonia, which can lead to lung failure in the further course.

More on this topic: Coronavirus- how dangerous is it?

Bacteria as the cause

Bacteria are less likely to cause the common cold. They are more likely to trigger a superinfection at the bottom of a viral cold. The process of a superinfection can look something like this: First a virus triggers a cold, which is fought by the immune system. In people with an immune deficiency or, in more rare cases, in otherwise healthy people, a simple cold can be followed by a second infection with a bacterium. This is called superinfection.

The infection with the bacterium then affects specific organs. For example, an infection in the lungs can lead to pneumonia or in the ear to otitis media. Of course, a bacterium can also cause a normal cold. However, as described above, this is much rarer than a viral cold. Doctors should therefore be very cautious about prescribing antibiotics for colds, as most are caused by viruses and are ineffective against these antibiotics.The use of an antibiotic can only make sense if a superinfection is suspected and there are additional symptoms to the typical cold symptoms.

Would you like to know more about bacterial infections? - Then read our article: Cold caused by bacteria

A streptococci

Streptococci are bacteria that are divided into groups A-streptococci and B-streptococci according to the way in which they break down the red blood pigment hemoglobin. The A-streptococci include the pneumococci (Streptococcus pneumoniae) and the viridans streptokokki.

Streptococci usually do not primarily trigger a cold, but more specific diseases of individual organs, which, however, can be favored by a viral cold. The pneumococci are discussed in more detail in a following section.

The viridans streptokokki occur in the oral cavity. They colonize dental plaques and can thus trigger tooth decay. That they cause a cold is rather untypical.

Staphylococci

Staphylococci are bacteria that can in principle trigger an infection in any organ system. The fact that staphylococci are the cause of a cold is very atypical. They are more likely to trigger infections in the skin or internal organs, such as endocarditis, i.e. inflammation of the inner lining of the heart.

Similar to streptococci, staphylococci can cause pneumonia, which can be a complication of a normal virus-induced cold.

Pneumococci

Pneumococci can be the cause of pneumonia, otitis media, inflammation of the nasal mucosa or meningitis, among other things. Such an infection with pneumococci is favored when the immune system is already weakened by a viral cold. This is especially the case with people who have weak immune systems for various reasons.

In children, pneumococci can trigger acute tonsillar angina, i.e. inflammation of the tonsils. But this is a far more acute illness than a cold.

Cold as a cause of a cold

The assumption that a cold is caused by the cold alone and, more precisely, by drafts, moisture or hypothermia is still widespread. However, cold alone cannot cause a cold and you can catch a cold even without first being exposed to the cold. Often the first symptom of a cold person is the feeling of "shivering".

This symptom is caused by an increase in body temperature due to messenger substances in the body's own defense system. So that the body temperature can be increased, there is a reduced blood flow and cooling of the skin, the body hair standing up (goose bumps) and an increase in muscle tone up to muscle tremors. These mechanisms lead to a feeling of coldness at the beginning of a cold, but it is not the cause of the disease, rather it is a consequence of the virus infection.

However, the cold can indirectly increase the risk of infection, as people are more often near infected people when it is cold, for example in buildings, public transport and poorly ventilated rooms. Another suspected connection between cold and a cold could be a weakening of the body's own defense system due to excessively long or intensive exposure to cold on an inadequately protected body, which can lead to a poorer defense against pathogens.

Read more on this topic at: Why do you get a cold from the cold?

Causes of a Chronic Cold

If you suffer from colds very often or if you also have allergies, there is a constant effect of irritations on the nasal mucosa. For example, a hypersensitive reaction of the mucous membrane can lead to chronic inflammation of the nasal mucous membrane and, very often, of the mucous membranes in the paranasal sinuses (Rhinosinusitis).

But anatomical changes in the nose and nasopharynx can also be causes of a chronic cold. A crooked nasal septum, for example, or other obstacles such as foreign bodies (often in children), enlarged turbinates or the consequences of surgical interventions in the area of the nose can cause a chronic cold. It is not uncommon, especially in children, that nasal polyps or an enlarged pharynx lead to permanent complaints.

Certain diseases that cause inflammation in different areas of the body can also lead to chronic inflammation in the nasal area. These include, for example, Wegener's granulomatosis, in which the blood vessels become inflamed, or sarcoid, a systemic disease that can also affect the nasal mucous membrane.

Mental and emotional causes of a cold

A cold can be promoted by psychological stress and especially by emotional stress. Stress at work or school, as well as stress in family or relationships, can lead to a weakened immune system. Often colds occur due to psychological and emotional stress, as a sign of the body's defensive weakness. In addition, psychological and emotional stress often leads to an unhealthy lifestyle, for example physical exercise and a balanced diet are given less attention due to lack of time. This also makes the body more susceptible to disease.

In bronchial asthma and allergies, it is also known that psychological factors are a cause of the disease. Mental stress can exacerbate the symptoms of allergy sufferers, and in around half of all asthma attacks, emotional factors are involved as possible triggers. However, similar to the so-called "nervous coughing", there also seems to be a psychological cause for frequent sneezing without any recognizable physical reason or accompanying colds. This phenomenon belongs to the group of so-called psychosomatic disorders and should be clarified psychiatrically.