Etiology
Acute respiratory infections are caused by viruses, bacteria or fungi that manifest in any area of the respiratory tract, including the nose, middle ear, throat, larynx, air passages, and lungs. The most common etiological agents responsible for ARI in children are:
Though the pathogens vary with the child's age, immune condition, and environment, most ARI episodes worldwide are caused by viruses (Childinfo, 2009). However, as many as two thirds of pneumonia cases are caused by both a bacteria and a virus (WHO, 2010). The fungal infection--pneumocystis jiroveci-- is estimated to cause at least 25% of all pneumonia deaths in HIV-infected infants (WHO, 2013). The devastating impact of ARIs is apparent not only due to its high mortality, but also in its considerable rate of morbidity and co-morbidity as well. Malnutrition and harsh living conditions put children at even higher risk of getting and dying from an ARI.
Transmission
In developing countries, bacterial infection plays a greater role in causing pneumonia than it does in developed countries. Nasopharyngeal transmission rates are twice as high in developing countries in comparison to developed countries, due to higher exposure to risk factors that increase bacterial colonization of the upper airways. This explains the higher frequency of bacterial ARI. In fact, the incidence of pneumonia in most developing countries is 10 times higher than that of the United States (McCracken, 2000).
Pathology
Pneumonia is an inflammation of the lungs caused by bacteria, viruses, fungi, or chemical irritants. It is a serious infection in which the air sacs fill with pus and fluid (Figure 3), limiting intake of oxygen. Pneumonia can be spread in a number of ways. 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 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 has critical importance for treatment and prevention (WHO, 2010).
Figure 3. Anatomical depiction of pneumonia
Pulmonary infection occurs when the normal defense mechanisms are overcome and microbes from an inhaled contaminant reach the peripheral air passages. This phenomenon causes edema (fluid build up) in the bronchi, bronchioles and alveoli, along with leukocyte (white blood cell) infiltration to the inflamed region. The congestion creates a perfect place for bacteria to grow and replicate. This process may stay circumscribed to an area or extend along the lungs. As consolidation takes place, the respiratory function reduces as vital capacity drops and the elasticity of the airways decreases. As bacteria and edema build up, air capacity of the lungs becomes compromised. Blood flow and ventilation of the involved areas is affected, altering the ventilation/perfusion relationship, resulting in decreased oxygenation and increased respiratory and cardiac workloads (this is why, in certain extreme cases of childhood pneumonia, patients might present with a bluish tinge to their fingers and the skin around their mouths).
When the effort to inhale increases, retraction of the lower part of the thorax occurs causing a perceptible horizontal extension of the ribs, a reliable sign of a severe restriction of pulmonary function which increases the risk of child death from pneumonia (McCracken, 2000).
Signs and Symptoms
There are a number of symptoms for ARI, particularly pneumonia, although many mimic those of other diseases. These include:
However, respiratory frequency is used to differentiate upper respiratory infection from pneumonia. The respiratory rate is the most sensitive and reliable index for evaluating the presence and severity of ARI, and is the current method recommended for use by health personnel. Training involves counting the respiratory rate (at rest) along with observing the breathing pattern and general state of the infant or child.
Depending on the symptoms, the World Health Organization (WHO) classifies pneumonia as: very severe pneumonia, severe pneumonia, pneumonia, and no pneumonia (WHO, 2005). The following chart shows the Integrated Management Tool for Pneumonia which shows criteria for classifying pneumonia (acute respiratory infection).
The complete IMCI guidelines can be downloaded in the following link:
IMCI newborn guidelines for HWs-1.pdf
The video below is of a child with distressed breathing. Try to count the breaths and observe the chest fluctuation in the child: .
Health, Economic, and Social Impact
Research has shown that prevention and proper treatment of pneumonia could avert one million deaths in children every year. With proper treatment alone, 600,000 deaths could be avoided. The cost of treating all children with pneumonia in 42 of the world's poorest countries is estimated at around US $600 million per year. Treating pneumonia in South Asia and sub-Saharan Africa - which account for 85% of deaths - would cost a third of this total. This price includes the cost of antibiotics as well as the cost of training health workers, which strengthens the health systems as a whole (WHO, 2010).