Definition

Acute Respiratory Infection, abbreviated as ARI, is an infection of the respiratory tract that tends to occur suddenly and can worsen rapidly. This infection can affect both the upper and lower respiratory tract. 

Anatomically, the upper respiratory tract begins from the nasal cavity to the vocal cords in the larynx, including the sinuses and middle ear. The lower respiratory tract includes the continuation of the upper respiratory tract, starting from the trachea and ending in the lungs. 

Upper Respiratory Tract Infection (URTI) is an infection affecting the nasal cavity, sinuses, pharynx, and larynx, while Lower Respiratory Tract Infection (LRTI) occurs in the trachea, bronchi, bronchioles, and lungs.

ARI is a contagious disease. Generally, ARI is transmitted through droplets. Additionally, ARI is known to be transmitted through contact with contaminated surfaces. Individuals with ARI can transmit it to others by:

• Coughing or sneezing without covering the mouth. This causes the virus or bacteria causing ARI to spread into the air and be inhaled by others.
• Covering the mouth with hands when coughing or sneezing, then touching someone else's hands. When that person touches their nose, mouth, or eyes, the virus or bacteria can enter their body and cause infection.

Causes

ARI can occur when viruses or bacteria enter the respiratory tract. Viruses or bacteria may enter your respiratory tract when you touch your mouth, nose, or eyes after touching a contaminated surface or shaking hands with a sick person.

The most common virus causing respiratory tract infections is the rhinovirus. Additionally, other viruses such as influenza virus, adenovirus, enterovirus, and respiratory syncytial virus can also cause respiratory tract infections. Bacteria are known to cause about 15% of acute-onset pharyngitis cases. The most common bacteria causing respiratory tract infections are S. pyogenes and Group A streptococcus.

Causes of upper respiratory tract infections (URTI) include:

• Acute ear infections can be caused by viral or bacterial infections, but the most common cause of acute ear infections is Streptococcus pneumoniae or Haemophilus influenzae.
• Acute pharyngitis can be caused by viral infections such as rhinovirus, influenza, and Epstein-Barr virus. Additionally, pharyngitis can be caused by bacterial infections.
• The common cold is caused by rhinovirus.

Causes of lower respiratory tract infections (LRTI) include:

• Bronchiolitis is generally caused by rhinovirus, respiratory syncytial virus (RSV), and human metapneumovirus.
• Bronchitis, generally caused by influenza virus and rhinovirus.
• Pneumonia is a common respiratory infection that varies by age, with causes ranging from viruses to bacteria. Additionally, SARS-CoV-2 is also known to cause pneumonia and other lower respiratory tract infections.

Risk Factor

Everyone is at risk of experiencing ARI. However, some individuals with the following factors are more likely to experience ARI. Some risk factors for ARI include:

• Children and the elderly have vulnerable immune systems to viral infections.
• Individuals with compromised immunity, such as those with cystic fibrosis, HIV, corticosteroid use, transplantation, and post-splenectomy, have a high risk of experiencing ARI.
• Individuals with lung diseases or problems.
• Individuals with asthma and allergic rhinitis have a higher likelihood of experiencing respiratory infections.
• Anomalies or anatomical shape abnormalities, such as facial dysmorphic changes or nasal polyps.
• Smokers have a higher risk of experiencing ARI and tend to have more difficulty recovering.

Symptoms

ARI symptoms may include:

• Cough
• Sneezing
• Blocked nose
• Red eyes
• Hoarse voice
• Sore throat
• Headache
• Muscle aches
• Fever
• Runny nose
• Fatigue and lack of energy
• Swollen lymph nodes

Diagnosis

ARI is usually diagnosed based on physical examination findings and symptoms reported by the patient. The doctor will examine your nose, ears, and throat and check your breathing. Generally, you do not need further tests to confirm the diagnosis of ARI.

If examination results suggest lung infection or other infections, you may need some of the following tests:

• Chest X-rays can help identify abnormalities in the respiratory tract, lungs, heart, bones, and blood vessels.
• Chest CT scans are performed with a large circular scanning machine and can be entered by adults lying down. Chest CT scans are aimed at detecting acute and chronic changes in the lungs.
• Lung function tests or spirometry are tests used to measure lung function. This test is done by measuring the air that enters and exits the lungs.
• Nasal swabs are performed to take samples from the nose. This procedure is done to examine viruses and bacteria causing respiratory infections. Nasal swabs are performed by tilting the head backward. After that, the examiner will gently insert a sterile applicator into your nostril. The applicator is rotated and left in place for 10-15 seconds. Then the applicator is removed from the nostril and inserted into a plastic tube for further examination.
• Throat swabs are performed in almost the same way as nasal swabs. The patient will be asked to tilt their head backward, and then the examiner will insert the applicator into the oropharynx. Rotate the applicator on the surface of the tonsils and the posterior wall of the pharynx. After that, remove the applicator from the oropharynx and insert it into a plastic tube for further examination.
• Sputum tests are performed to detect bacteria causing respiratory tract infections.

Management

Most cases of ARI can improve without treatment. However, treatment may be necessary for ARI with severe symptoms. The management of ARI is based on the pathogen causing the infection. Infections caused by viruses usually resolve on their own, and antibiotics cannot treat viral infections. Antibiotics may be used for infections caused by bacteria. Additionally, the doctor will prescribe medications to relieve your symptoms.

Complications

Some complications that can arise from ARI include:

• Respiratory failure: an increase in CO2 in the body due to impaired lung function
• Breathing cessation can occur when the lungs stop functioning
• Heart failure

Prevention

To reduce the risk of ARI, you can take several preventive measures, such as:

• Regular handwashing
• Covering the mouth with a tissue or sleeve when coughing and sneezing
• Dispose of used tissues properly
• Avoid touching the face, especially the nose, eyes, and mouth
• Quit smoking
• Consume vitamin C to boost the immune system

When to See a Doctor?

Immediately consult a doctor if you experience the above symptoms accompanied by:

• Coughing up blood or mucus with blood
• Coughing for more than 3 weeks
• Aged over 65
• Having a weak immune system
• Having a history of heart, lung, or kidney disease