What is Lower Respiratory Tract Infection?
The lower respiratory tract begins from the trachea and ends in the lungs. The tract enters the lungs and divides into the bronchi. Then each of the bronchi divides further into smaller air pipes that are bronchioles. The bronchioles appear from the secondary and tertiary bronchi. These bronchioles end in small air sacs which are known as alveoli. Many alveoli bunch up together and form the alveolar sac. From these alveoli the blood capillaries go out. The exchange of air occurs in every alveolus and the capillaries which go out of these alveolar sacs and spread throughout the body carry the blood which came in from veins spread in the body.
The infection which occurs in the lower respiratory tract of human body is usually termed by the doctors as lower respiratory tract infection. The infections begin from the lower larynx and can also attack the bronchi and even the whole lungs. The common illnesses are bronchiolitis, pneumonia, bronchitis and flu.
The viruses which cause lower respiratory tract infection spread over the tract slowly. The diseases are mostly contagious in nature. Through direct contact with the patient of by inhaling the air which contains the germs you can get the same illness. Like the upper respiratory tract infections, lower respiratory tract infection spreads very fast and these infections cause greater harm to the human body than the upper respiratory infections.
Causes of Lower Respiratory Tract Infection
The primary cause of lower respiratory tract infection are the various kinds of viruses that attack our system. The viruses that enter our body often take the shape of structural proteins and hence can pass through unrecognised by the immunity system. Also the viruses secrete some of the toxins which are stronger than our immune system and thus our immunity drops down further and we get attacked by them. Some of these viruses enter in their 1st stage and thus they have a cover which the immunity system cannot penetrate or even identify as danger. Then the viruses incubate for a certain period of days and then the fully grown viruses attack the system. Within the incubation period the viruses learn about the immune system of the body and thus can fight them easily to spread the disease.
Common lower respiratory tract infections include:
- Bronchitis is a common lower respiratory tract infection. There are 2 kinds of Bronchitis; acute and chronic. The virus swells the bronchial tubes which causes difficulty in breathing, thus the infection affects the airways. The main virus which causes the disease is the same that causes the flu. Often the viruses of influenza and pneumonia attack the patient at the same time. About 4% of the people in a population of 1000 are affected by this virus. Whether the disease is chronic or acute is decided by the stage of the virus and the presentation of its structure.
- Pneumonia is another lower respiratory tract infection. It is caused by the virus streptococcus pneumoniae. The virus causes a great damage to the lung and the mortality rate is 25% of the patients affected by the virus. If a child below the age of 5 is affected, then he or she might not survive at all. Though this is generally not contagious but if your immunity is low then being in direct contact with the cough discharges may pass on the virus on you.
- Flu is caused by the influenza viruses and affects both the upper and the lower respiratory tracts.
- Bacterial meningitis caused by the virus Neisseria meningitides can cause lower respiratory tract infection.
- Scarlet fever cause by Group A strep.
- Tuberculosis cause by the bacteria mycobacterium tuberculosis which causes a consistent damage to the lungs.
- Bronchiolitis is also a lower respiratory tract infection. It is caused by RSV or respiratory syncytial virus. It mainly affects the respiratory tracts and the airways of little children.
Signs and Symptoms of Lower Respiratory Tract Infection
The primary signs and symptoms of any lower respiratory tract infection is coughing. Often the coughing is followed by mucus discharges. As you cough you, the phlegm may come out of your mouth. This is the sign of deterioration and thus cannot be ignored as common cold. Soon the other signs and symptoms like high temperature, dizziness, feeling a pressure or heaviness in your chest, shortness of breathing or breathing at an increased rate follow. Also blocking of nose, watering of nose and increased heart beat can be the symptoms of lower respiratory tract infection. Asthma attacks may also occur. As the lung gets affected, the breathing problem becomes acute. In case of pneumonia, the body temperature rises too high that it may also affect the brain. Your immune system becomes very weak, you start feeling weak hence. The viruses may also attack your nervous system which can cause sclerosis.
The health of the patient worsens slowly over a period of a week. In the beginning the symptoms may resemble that of a common cold or flu but then body aches begin and you feel like you are not being able to breathe and your fever goes on increasing.