Autumn: a change of season, the days get shorter, winter approaches accompanied by the cold and wet… and viruses take the opportunity to attack us when our body is weakened!
Colds, flu, coughs, bronchitis, winter illnesses affecting the respiratory system are the main reason for visiting the doctor between October and March. Although some get off scot free, others are affected on a regular basis, so the microbe is not solely responsible. For these people, strengthening the immune system is vital.
The respiratory tract, a point of entry for microbes
Most respiratory illnesses are caused by a virus. Sensitive to heat, the lower temperatures that arrive in Autumn are favourable for their development. This is also the reason why, with viral infections, the body defends itself by raising the body temperature to above 37.5°C, with the aim of destroying the virus: a fever develops. But how does the virus get into our body? The transmission of seasonal winter viruses is mainly via the airways: when coughing or sneezing, droplets carrying the virus are suspended in the ambient air and pass into the respiratory tract. The virus then contaminates cells and multiplies very rapidly, especially if the immune system is compromised. After several days of incubation, the symptoms appear: runny nose, cough, pain and tingling, fatigue, stiffness… The infection lasts one week on average, with a few more days of recovery.
Rhinoviruses and flu arrive with winter
Rhinoviruses and the influenza virus, or flu virus, highly contagious, are responsible for the respiratory disease outbreaks that frequently occur in winter.
There are more than 100 rhinoviruses, mostly causing illnesses of the upper airways, particularly colds. They are also one of the main causes of bronchial illnesses (bronchitis, bronchiolitis in children, pneumonia).
Flu viruses are more aggressive. Distinction is made between annual infectious seasonal influenza linked to known viruses and pandemic influenza which occurs several times a century, when new and highly contagious viral strains emerge: as was the case with influenza A, known as H1N1. Flu affects more than 2 million people every year in France*, and leads to hundreds of thousands of deaths throughout the world. Serious cases mainly occur in subjects at risk: the elderly, young children. Fortunately, our respiratory system knows how to protect itself!
*INVS (French Institute for Public Health Surveillance) data collected by the Reseau Sentinelles
A close connection between the mucosa and the immune system
The natural defences of the respiratory system:
The constant exposure of the respiratory tract to inhaled particles requires effective defence mechanisms to combat the invasion of microbes.
The air that we breath passes through several filtrations, including the first and most basic, the hairs in the nose. Then, within the respiratory mucosa, cilia located on the surface of the cells filter impurities, whose expulsion is carried out mechanically by coughing.
In addition to this, mucus is secreted by the cells in the respiratory system. This fluid covers the cilia and participates in the capture of contaminants and their expulsion via the cough. The mucus also contains antimicrobial compounds as well as numerous antibodies secreted by the B lymphocytes and respiratory mucosa.
The respiratory system, just like the intestine, has many immune cells gathered together in the form of cell clusters, mainly in the bronchial tubes.
More particularly, T lymphocytes are present in the upper respiratory tract. They produce molecules (cytokines) which are involved in the broad activation of the immune system, and some are also able to directly eliminate pathogens.
In the pulmonary alveoli, numerous cells supplement this immune action. They are active in the recognition and/or elimination of pathogens.
The respiratory system is itself also inhabited by a microbiota!
We know that the intestinal microbiota, previously known as the intestinal flora, plays a key role in the intestinal immune response (find out more). And yet several recent studies have revealed the existence of a microbiota in the respiratory tract, up until now regarded as a sterile environment in a healthy subject.
Even more astonishing, this proves that the intestinal microbiota regulate not only the global immune response of the body but also of the lungs!
In fact, a change in the intestinal microbiota can disrupt lung immunity and encourage respiratory illnesses.
Conversation between the lungs and the intestines
Several assumptions have been made regarding the existence of "communication" between intestinal and pulmonary microbiotas. This takes place via the secretion of microbial molecules which pass into the blood stream.
In addition, "microbe migrations" may occur between the 2 microbiotas. Several studies have actually shown that microorganisms deposited in the nasal cavity can be found a short time later in the gastro-intestinal tract.
In addition to this, the intestinal microbiota regulates intestinal immunity but also, remotely, that of the respiratory tract. Immune cells are able to migrate into the respiratory system, where they will activate local pulmonary immunity.
Winter pathologies and taking antibiotics
Winter pathologies and taking antibiotics
In France, 72 % of prescriptions for antibiotics are for respiratory tract illnesses, and particularly for winter pathologies.
This use of antibiotics is often not necessary because most of the time winter pathologies are caused by viruses, while antibiotics are only effective against bacteria.
Decreasing the consumption of antibiotics would reduce side-effects, particularly for disturbances of the digestive microbiota, diarrhoea and colitis, and limit the build-up of antibiotic resistance, a major problem for public health.
Tips for strengthening the immune system
Vitamin C Vitamin C, a powerful antioxidant, enables the manufacture of antibodies, and provides good resistance to infection particularly viral. Also, it supports the tone and dynamism of the body, and helps combat winter fatigue.
In seasonal vegetables and fruit: Brussels sprouts, kale, lemon, kiwi fruit, orange, grapefruit, lychees.
Vitamin D Vitamin D stimulates the immune defences to fight quite a few infections (flu, bronchitis, colds). When faced with an infectious agent, it induces the production of an anti-microbial peptide, cathelicidin, via the immune cells.
In oily fish, cod liver, eggs and offal.
Phytotherapy Certain plants have a recognised beneficial effect on the immune system, either as a preventive measure or alongside conventional treatments. Whereas some stimulate the natural defences, others act directly on the pathogens.
Essential oils The inhalation of essential oils, concentrates of active ingredients, is a good way to rid the ambient air of unstable pathogens, clear the respiratory tract and stimulate the pulmonary immune system.
Essential tea tree oils, peppermint, eucalyptus, saro.
Probiotics Taking probiotics consolidates the body's barrier systems. As previously stated, they have a positive effect in the prevention and on the symptoms of respiratory tract infections. Moreover, a healthy intestinal microbiota enables the proper regulation of the pulmonary immune system.
In fermented products (kefir, sauerkraut), yoghurt.