Causes and forms of a cold
The symptoms of coughing with increased sputum, sore throat, headache and aching limbs and running nose can occur individually or together, which would then lead to the full picture of the cold. In the vast majority of cases, a cold is always a part of the common cold. Depending on the duration of the cold and the amount of nasal secretion produced, the sinuses may also be involved (sinusitis), which would manifest itself as moderate to severe headaches and tapping pains over the corresponding sinuses.
In the vast majority of cases, the factors that cause colds are viruses. It is also possible that a bacterial infection (bacterial superinfection or secondary infection) follows after the onset of the disease, which must then be treated with antibiotics. So far, about 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 the common cold: the family of Coronaviridae includes the coronavirus with several subtypes, the family of Picornaviridae includes the human rhinovirus with more than 100 subgroups, Coxsackie viruses, echoviruses and human enteroviruses. The virus family Paramyxoviridae includes human parainfluenza viruses with some subtypes, human metapneumovirus and human respiratory syncytial virus (HRSV).
The group of adenoviruses includes the human adenovirus with some subtypes and the mastadenovirus. Furthermore, different subtypes of the virus family Reoviridae can cause colds. Rhinoviruses are the most common cause of the common cold (40% of cases), followed by coronaviruses (10%-25%) and HRSV (10-15%).
The metapneumovirus mainly causes cold symptoms in small children. A distinction is made between enveloped and non-enveloped virus forms. While the non-enveloped viruses can mostly 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 disease progression.
Furthermore, enveloped viruses are able to mutate earlier and faster, i.e. to change their protein composition of the outer layer in a way that the immune system cannot adapt to them. The constant change in the virus structure and the associated variability explains why cold infections in humans can occur so frequently. Viruses can survive particularly well in a humid environment, which explains why most colds occur in the months September to November.
Contrary to popular and persistent opinion, cold and wet weather alone cannot cause colds in humans. Numerous studies and investigations by the U.S. Navy have shown that there is no correlation between exposure to cold and moisture and the development of a cold. The Navy allowed numerous swimmers to 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 to be able to trigger a cold. The cold and wet alone are not enough.
However, more recent studies have shown that the two factors cold and wet can have a secondary influence on the risk of developing the disease. In order to ward off an infection, a well-functioning immune system is essential. The study found that this system does not work properly in very cool environments and thus represents a possible entry point for pathogens.
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