Respiratory infections, as the name indicates, refer to infection in any part of the respiratory system. It may affect sinuses, nose, throat, tonsils, airways, or lungs. The common cold is a very common form of respiratory infection that affects many people. Respiratory infections are broadly classified into upper respiratory infections and lower respiratory infections.
Upper respiratory infections affect the organs and tissues of the chest including nose, throat, tonsils, larynx and sinuses. Some common upper respiratory infections are cold, sinusitis, throat infection, tonsillitis, laryngitis, flu, and whooping cough.
Lower respiratory tract infections affect trachea, windpipe, and lungs. Bronchitis, bronchiolitis, croup, influenza, and pneumonia are categorized as lower respiratory tract infections.
Upper respiratory tract infections are found to be more common than lower respiratory infections. Respiratory infections are more common in children than adults, as the immune system is not completely developed in children.
Respiratory infections are categorized into acute and chronic respiratory infections. Chronic respiratory infections occur repeatedly and have a gradual onset, while acute infections have a sudden onset and the symptoms worsen soon.
Some common chronic respiratory infections are asthma, chronic bronchitis, rhinitis, and chronic sinus infections. Chronic respiratory infections are characterized by symptoms like shortness of breath, fatigue, mucus production, fever, sore throat, and cough.
A runny nose, nasal congestion, cough, sneezing, and sputum is the most common symptoms of acute respiratory infections. Fever, fatigue, headache, wheezing, and difficulty in swallowing are also noticed as symptoms of acute respiratory infections.
Major risk factors for chronic infections include age above 65 years, being women, socially and economically underprivileged people, and people with a history of asthma. Children have an increased risk of getting acute respiratory infections due to the underdeveloped immune system.
People with a history of cardiac and lung diseases also have a high risk of developing this infection. Low humidity in the environment and a weak immune system also enhance the risk of respiratory infections.
Respiratory infections are caused by viruses and bacteria. A number of viruses including rhinovirus, adenovirus, Coxsackie virus, parainfluenza virus, respiratory syncytial virus, and human metapneumovirus.
Streptococcus, chlamydia, Neisseria, and Corynebacterium cause respiratory infections. The respiratory examination is used to check for the patient’s breathing pattern. Fluid accumulation and lung inflammation is also revealed through this method.
Other diagnostic tools include lung function tests. Pulse oximetry measures the amount of oxygen the gets into the lungs at the time of breathing. Sputum culture and analysis is used to identify the causative organism. Lateral neck x-rays, chest x-ray, and CT scan are also used for confirmation of diagnosis.
Treatment of chronic respiratory infections depends on the symptoms. A nasal wash helps in alleviating sinus problems. Airway clearance devices are used to reduce the symptoms in lower respiratory tract infections.
Infections are treated with medications like antibiotics as in the bacterial infection. In some viral infections, antiviral medications are prescribed. Inhaled medications that make breathing easy are also recommended.
Upper respiratory tract infections are treated symptomatically. Cough suppressants, vitamin C, and zinc are used to reduce symptoms or to shorten the duration of the symptom. Nasal decongestants, steam inhalation, and analgesics are suggested to provide relief. When left untreated, respiratory infections may lead to complications.
Most of the upper respiratory tract infections are caused by viral infections. Some of the viral agents that result in this type of respiratory infection include rhinoviruses, coronaviruses, adenoviruses, and Coxsackie virus. In most of the cases, the same viral agent causes respiratory infection in both children and adults.
Nasopharyngitis – symptoms of common cold are caused by rhinoviruses, coronaviruses, enteroviruses, adenoviruses, orthomyxoviruses, paramyxoviruses, RSV, human metapneumovirus, bocavirus, and EBV. Unidentified viruses are also implicated in causing common cold in adults. Some other infections like varicella, rubeola, and rubella infections have a common cold as one of the symptoms.
Pharyngitis – this may be caused by both viral and bacterial infections. Viral agents that cause pharyngitis include adenovirus, influenza virus, Coxsackie virus, herpes simplex virus, infectious mononucleosis virus, and cytomegalovirus. Pharyngitis may be caused by bacterial infections like group A, C, and G Streptococci, Neisseria gonorrhoeae, Corynebacterium diphtheriae, atypical bacteria, and anaerobic bacteria.
Rhinosinusitis – viral causes of rhinosinusitis is similar to that of nasopharyngitis -- rhinoviruses, coronaviruses, enteroviruses, adenoviruses, influenza A and B viruses, and RSV. Bacterial causes of rhinosinusitis include Streptococcus pneumoniae, Haemophilus influenza, Moraxella catarrhalis, and Staphylococcus aureus. In some rare cases, C pneumoniae and Neisseria species may also cause rhinosinusitis.
Epiglottitis – this condition is caused by bacterial infection. Hemophilus influenzae type b is implicated in the majority of the cases of epiglottitis. Group A Streptococci, S pneumoniae, and M catarrhalis may cause this condition in children.
Laryngotracheitis – also known as croup, laryngotracheitis is caused by human parainfluenza virus type 1, 2, and 3. influenza viruses and RSV may also lead to croup. Other forms of laryngitis are caused by viral infections including rhinovirus, coronavirus, adenovirus, influenza virus and RSV.
Bacterial causes of croup include Corynebacterium diphtheria, Chlamydia pneumoniae, Mycoplasma pneumoniae, Moraxella catarrhalis, H influenza, and S aureus. Lower respiratory tract infections affect the windpipe and lungs.
Bronchitis – bronchitis is caused by influenza virus A and B and also by the bacteria Mycoplasma pneumoniae. Other viral agents that cause lower respiratory infections include parainfluenza virus, RSV, coronaviruses, and adenoviruses.
Bronchiolitis – this is characterized by the infection of bronchioles and is usually caused by viral infection. Respiratory syncytial virus or RSV is the most common cause of bronchiolitis, but other viruses like rhinovirus and influenza virus may also cause infection of bronchioles. Bacterial cause of bronchiolitis is rare.
Croup – or infection of windpipe is a common condition among children. It is commonly caused by viruses. Parainfluenza virus, influenza viruses A and B, and RSV may result in croup. In some cases, bacteria like Corynebacterium diphtheria, Chlamydia pneumoniae and Mycoplasma pneumoniae may lead to croup.
Influenza – influenza viruses A and B cause flu or influenza.
Pneumonia – inflammation of the lung tissue is referred to as pneumonia. Infection of lungs may be caused by viral and bacterial causes. Bacterial causes of pneumonia are Streptococcus pneumoniae, Chlamydophila pneumonia or Legionella pneumophila. Respiratory viruses and mycoplasma infection may also lead to pneumonia.
3 Diagnosis and Treatment
A review of the current condition and the medical history of the patient provide important clues regarding the causes.
During the physical examination, heart and breathing rate, and ear infections are noted.
Diagnostic tests used include:
X-ray – chest x-ray is often suggested for the confirmatory diagnosis of pneumonia. Lateral neck x-rays are often used to rule out chances of epiglottitis, particularly when the patient has breathing difficulties.
CT scan – this is not very commonly used in the diagnosis of respiratory infections. It is mostly recommended if the symptoms are severe and are not typical of respiratory infection.
Laboratory tests – lab-based tests are sometimes recommended for the diagnosis of respiratory infections. It is usually suggested to identify the causative organism. Sputum test is done by analyzing a sample of sputum to identify the specific bacteria or virus.
Nasal or throat swabs are also used in the diagnosis. In this procedure, cells from the nasal mucus, throat or tonsils are taken using a cotton swab. The sample is then analyzed in the laboratory to identify the causative agent.
Throat swab uses rapid antigen detection to identify group A beta-hemolytic strep bacteria. A urine test also helps in identifying bacterial infections. This is useful in the identification of Streptococcus pneumoniae or Legionella pneumophila infection.
Many types of respiratory tract infections do not have a specific treatment. Common cold, sore throat and flu are treated at home. Treatment recommended for a particular infection depends on the type of infection, causative agent, symptoms and its severity, and risk of complications.
Respiratory infections caused by viruses cannot be treated by antibiotics. Antibiotics are recommended for serious bacterial infections like a whooping cough. It is also suggested for people who have other medical conditions like type 1 or type 2 diabetes. Antibiotics are useful in alleviating the symptoms of infections in people who have an increased risk of complications.
Symptoms of respiratory infections can be reduced by medicines including paracetamol and ibuprofen that help to relieve pain and fever. Decongestants and nasal sprays are useful in controlling nasal congestion.
Over-the-counter medications like a cough and flu drugs and some complementary medications are commonly used in alleviating the symptoms of respiratory infections. Symptoms of upper respiratory tract infection can be reduced by steam inhalation and gargling with salt water.
Many of the respiratory infections can be prevented successfully. Washing hands help to reduce the exposure to agents that spread the infection. One should avoid close contact with people who have respiratory infections.
Covering nose and mouth while around people who have infections also is a way to prevent the spread of infection. To prevent the introduction of causative organisms into the body, avoid touching the face, especially nose and mouth.
One can improve the functioning of the immune system by including more of vitamin C in the diet. When left untreated, respiratory infections may lead to complications like respiratory arrest, respiratory failure, or congestive heart failure.
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