February 23, 2024

Acute Respiratory Infection Definition, Causes, Prevention, Treatment, Pneumonia

Acute Respiratory Infection Definition, Causes, Prevention, Treatment, Pneumonia


Respiratory infections often have strong seasonal patterns, with temperate climates more affected during the winter. Several factors explain winter peaks in respiratory infections, including environmental conditions and changes in human behaviours. Viruses that cause respiratory infections are affected by environmental conditions like relative humidity and temperature. Temperate climate winters have lower relative humidity, which is known to increase the transmission of influenza.

Of the viruses that cause respiratory infections in humans, most have seasonal variation in prevalence. Influenza, Human orthopneumovirus (RSV), and human coronaviruses are more prevalent in the winter. Human bocavirus and Human metapneumovirus occur year-round, rhinoviruses (which cause the common cold) occur mostly in the spring and fall, and human parainfluenza viruses have variable peaks depending on the specific strain. Enteroviruses, with the exception of rhinoviruses. tend to peak in the summer.

Acute respiratory infections (ARIS) are classified as upper respiratory tract infections (URIS) or lower respiratory tract infections (LRIS). Lower respiratory infections, such as pneumonia, tend to be far more severe than upper respiratory infections, such as the common cold.

Upper respiratory tract infection :

The upper respiratory tract is considered the airway above the glottis or vocal cords; sometimes, it is taken as the tract above the cricoid cartilage. This part of the tract includes the nose, sinuses, pharynx, and larynx.

Typical infections of the upper respiratory tract include tonsillitis, pharyngitis, laryngitis, sinusitis, otitis media, certain influenza types, and the common cold. Symptoms of URIS can include cough, sore throat, runny nose, nasal congestion, headache, low-grade fever, facial pressure, and sneezing.

Lower respiratory tract infection :

The lower respiratory tract consists of the trachea (windpipe), bronchial tubes, bronchioles, and the lungs

Lower respiratory tract infections are generally more severe than upper respiratory infections. LRIS are the leading cause of death among all infectious diseases. The two most common LRIS are bronchitis and pneumonia. Influenza affects both the upper and lower respiratory tracts, but more dangerous strains such as the highly pernicious H5N1 tend to bind to receptors deep in the lungs.


Pneumonia accounts for 15% of all deaths of children under 5 years old, killing 808 694 children in 2017. Pneumonia can be caused by viruses, bacteria, or fungi. Pneumonia can be prevented by immunization, adequate nutrition, and addressing environmental factors. Pneumonia caused by bacteria can be treated with antibiotics, but only one-third of children with pneumonia receive the antibiotics they need.

Pneumonia is a form of acute respiratory infection that affects the lungs. The lungs are made up of small sacs called alveoli, which fill with air when a healthy person breathes. When an individual has pneumonia, the alveoli are filled with pus and fluid, which makes breathing painful and limits oxygen intake.

Pneumonia is the single largest infectious cause of death in children worldwide. Pneumonia killed 808 694 children under the age of 5 in 2017, accounting for 15% of all deaths of children under five years old. Pneumonia affects children and families everywhere but is most prevalent in South Asia and sub-Saharan Africa. Children can be protected from pneumonia, it can be prevented with simple interventions, and treated with low-cost, low-tech medication and care.

 Causative agent:

Pneumonia is caused by a number of infectious agents, including viruses, bacteria and fungi. The most common are: Streptococcus pneumoniae-the most common cause of bacterial pneumonia in children;

Haemophilus influenzae type b (Hib)- is the second most common cause of bacterial pneumonia: the respiratory syncytial virus is the most common viral cause of pneumonia. in infants infected with HIV, Pneumocystis jiroveci is one of the most common causes of pneumonia, responsible for at least one-quarter of all pneumonia deaths in HIV-infected infants. 

Mode of Transmission:

Pneumonia can be spread in a number of ways.

Respiratory tract infection 

Droplet infection 

Droplet nuclei ( through coughing, sneezing, talking)

The viruses and bacteria that are commonly found in a child’s nose or throat, can infect the lungs if they are inhaled. They may also spread via air-borne droplets from a cough or sneeze. In addition, pneumonia may spread through blood. especially during and shortly after birth. More research needs to be done on the different pathogens causing pneumonia and the ways they are transmitted, as this is of critical importance for treatment and prevention.

Signs and symptoms: 

In children under 5 years of age, who have cough and/or difficult breathing, with or without fever, 

pneumonia is diagnosed by the presence of either fast breathing or lower chest wall indrawing where the chest moves in or retracts during inhalation (in a healthy person, the chest expands during inhalation). Wheezing is more common in viral infections

Very severely ill infants may be unable to feed or drink and may also experience unconsciousness.

hypothermia and convulsions.

Risk factors :

While healthy children can fight the infection with their natural defences, children whose immune systems are compromised are at higher risk of developing pneumonia. A child’s immune system may be weakened by malnutrition or undernourishment, especially in infants who are not exclusively breastfed.

Pre-existing illnesses, such as symptomatic HIV infections and measles, also increase a child’s risk of contracting pneumonia.

The following environmental factors also increase a child’s susceptibility to pneumonia: 

Indoor air pollution is caused by cooking and heating with biomass fuels (such as wood or dung)

Living in crowded homes

Parental smoking.


Pneumonia should be treated with antibiotics. The antibiotic of choice is amoxicillin dispersible tablets. Most cases of pneumonia require oral antibiotics, which are often prescribed at a health centre. These cases can also be diagnosed and treated with inexpensive oral antibiotics at the community level by trained community health workers. Hospitalization is recommended only for severe cases of pneumonia. 

Prevention and Control : 

Preventing pneumonia in children is an essential component of a strategy to reduce child mortality. Immunization against Hib, pneumococcus, measles and whooping cough (pertussis) is the most effective way to prevent pneumonia.

Adequate nutrition is key to improving children’s natural defences, starting with exclusive breastfeeding for the first 6 months of life. In addition to being effective in preventing pneumonia, it also helps to reduce the length of the illness if a child does become ill. Addressing environmental factors such as indoor air pollution (by providing affordable clean indoor stoves, for example) and encouraging good hygiene in crowded homes also reduces the number of children who fall ill with pneumonia. In children infected with HIV, the antibiotic cotrimoxazole is given daily to decrease the risk of contracting pneumonia.

Many more have integrated diarrhoea and pneumonia specific action into their national child health and child survival strategies. For many countries, the post-Millenium Development Goal agenda has explicitly included ending preventable diarrhoea and pneumonia deaths as a priority action.

WHO response

The WHO and UNICEF integrated Global action plan for pneumonia and diarrhoea (GAPPD) aims to accelerate pneumonia control with a combination of interventions to protect, prevent, and treat pneumonia in children with actions to: 

Protect children from pneumonia including promoting exclusive breastfeeding and adequate complementary feeding:

Prevent pneumonia with vaccinations, handwashing with soap, reducing household air pollution, HIV prevention and cotrimoxazole prophylaxis for HIV-infected and exposed children;

Treat pneumonia focuses on making sure that every sick child has access to the right kind of care either from a community-based health worker or in a health facility if the disease is severe and can get the antibiotics and oxygen they need to get well.

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