|Year : 2016 | Volume
| Issue : 1 | Page : 1-4
Acute respiratory infections in children: Can we prevent?
Gajanan S Gaude
Department of Pulmonary Medicine, KLE University, J.N. Medical College, Belgaum, Karnataka, India
|Date of Web Publication||8-Jun-2016|
Dr. Gajanan S Gaude
Department of Pulmonary Medicine, KLE University, J.N. Medical College, Belgaum - 590 010, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gaude GS. Acute respiratory infections in children: Can we prevent?. Indian J Health Sci Biomed Res 2016;9:1-4
The upper respiratory tract consists of the airways from the nostrils to the vocal cords in the larynx, including the paranasal sinuses and the middle ear. The lower respiratory tract covers the continuation of the airways from the trachea and bronchi to the bronchioles and the alveoli. Acute respiratory infections (ARIs) are not confined to the respiratory tract and have systemic effects because of the possible extension of infection or microbial toxins, inflammation, and reduced lung function. ARIs are the most common causes of both illness and mortality in children under five, which averages three to six episodes of ARIs annually regardless of country or economic situation. However, the proportion of mild-to-severe disease varies between high- and low-income countries, and because of the differences in specific etiologies and risk factors, the severity of lower respiratory infections (LRIs) in children under five is worse in developing countries, resulting in a higher case-fatality rate. Although medical care can mitigate both severity and fatality to some extent, many severe LRIs do not respond to therapy, largely because of the lack of highly effective antiviral drugs. Some 10.8 million children die each year. The World Health Organization (WHO) estimates that 2 million children under five die of pneumonia each year. Worldwide, about 85–88% of the ARI episodes are acute upper respiratory infections (URIs) while the remaining are acute LRIs.
| Burden of Disease|| |
URIs are the most common illness seen in childhood period. They include rhinitis (common cold), sinusitis, ear infections, acute pharyngitis or tonsillopharyngitis, epiglottitis, and laryngitis. The vast majority of URIs has a viral etiology. Rhinoviruses account for 25–30% of the URIs; respiratory syncytial viruses (RSVs), parainfluenza and influenza viruses, human metapneumovirus, and adenoviruses for 25–35%; corona viruses for 10%; and unidentified viruses for the remainder. Because most URIs are self-limiting, their complications are more important than the infections. Acute viral infections predispose children to bacterial infections of the sinuses and middle ear, and aspiration of infected secretions and cells can result in LRIs. The common LRIs in children are pneumonia and bronchiolitis. The respiratory rate is a valuable clinical sign for diagnosing acute LRI in children who are coughing and breathing rapidly. The presence of lower chest wall indrawing identifies more severe disease. Currently, the most common causes of viral LRIs are RSVs. They tend to be highly seasonal, unlike parainfluenza viruses, the next most common cause of viral LRIs. The epidemiology of influenza viruses in children in developing countries deserves an urgent investigation because safe and effective vaccines are available. Due to the effective use of measles vaccine, the prevalence of this infection in children has come down.
ARIs are a major burden to respiratory infections in developing countries such as India. They are the leading cause of death among children under 5 years of age in developing countries, resulting in nearly 1.9 million childhood deaths per year, of which 20% are estimated to occur in India. In the most recent estimate of acute lower respiratory infection-associated mortality in India, pneumonia was held to be responsible for 369,000 deaths (28% of all deaths) in children below 5 years, making it the single most important killer in this age group. ARIs also impose a significant economic burden on health-care systems and individual families in developing countries. Recently, it has been estimated that among children aged <5 years, the median direct cost of ARI was US$ 135 in private and US$ 54 in public institutions. Studies from Bangladesh and Pakistan estimate the average cost of treatment for a single episode of pneumonia as US$ 13 for outpatient care and US$ 71 to US$ 235 for severe hospitalized pneumonia. It was also estimated that 75% of the families spent more than half of their total monthly expenditure on hospitalization.
Both bacteria and viruses can cause pneumonia in children. Bacterial pneumonia is often caused by Streptococcus pneumoniae (pneumococcus) or Haemophilus influenzae, mostly type b (Hib) and occasionally by Staphylococcus aureus or other streptococci. Other pathogens, such as Mycoplasma pneumoniae and Chlamydia pneumoniae, cause atypical pneumonia, and the prevalence of these pathogens in children is rare. The burden of LRIs caused by Hib or S. pneumoniae is difficult to determine because current techniques to establish bacterial etiology lack sensitivity and specificity. It has been reported that S. pneumoniae and Hib account for 13–34% and 1.4–42.0% of bacterial pneumonia, respectively, whereas another study  has reported that Hib accounts for 5–11% of pneumonia cases. Upper respiratory tract colonization with potentially pathogenic organisms and aspiration of the contaminated secretions has been implicated in the pathogenesis of bacterial pneumonia in children. Infection of the upper respiratory tract with influenza virus or RSVs has been shown to increase the binding of both H. influenzae and S. pneumoniae in the nasopharynx. This finding may explain why there are increased rates of pneumococcal pneumonia parallel to influenza and RSV epidemics. A study in South Africa showed that vaccination with a 9-valent pneumococcal conjugate vaccine reduced the incidence of virus-associated pneumonia causing hospitalization by 31%, suggesting that pneumococcus plays an important role in the pathogenesis of virus-associated pneumonia. Viruses are responsible for 40–50% of infection in infants and children hospitalized for pneumonia in developing countries. Measles virus, RSVs, parainfluenza viruses, influenza type A virus, and adenoviruses are the most important causes of viral pneumonia. Differentiating between viral and bacterial pneumonias radiographically is difficult, partly because the lesions look similar and partly because bacterial superinfection occurs with influenza, measles, and RSV infections. In developing countries, the case-fatality rate in children with viral pneumonia ranges from 1.0% to 7.3%, with bacterial pneumonia from 10% to 14%, and with mixed viral and bacterial infections from 16% to 18%. Entry of bacteria from the gut which spread through the bloodstream to the lungs has also been proposed for the pathogenesis of Gram-negative organisms, but such bacteria are uncommon etiological agents of pneumonia in immune-competent children.
Bronchiolitis occurs predominantly in the 1st year of life and with decreasing frequency in the 2nd and 3rd years. Because the signs and symptoms are also characteristic of pneumonia, health-care workers may find it difficult in differentiating between bronchiolitis and pneumonia. Two features that may help are a definition of the seasonality of RSVs in the locality and the skill to detect wheezing. RSVs are the main cause of bronchiolitis worldwide and can cause up to 70 or 80% of LRIs during high season. Even though influenza viruses usually cause URIs in adults, they are increasingly being recognized as an important cause of LRIs in children and perhaps the second most important cause after RSVs of hospitalization of children with ARI.
| Preventing Respiratory Infection in Children|| |
Interventions to control ARIs in children can be divided into four basic categories: immunization against specific pathogens, early diagnosis and treatment of disease, improvements in nutrition, and safer environments. The first two preventive strategies fall within the purview of the health-care system, whereas the last two fall under public health and require multi-sectoral involvement.
Widespread use of vaccines against measles, diphtheria, pertussis, Hib, pneumococcus, and influenza has the potential to substantially reduce the incidence of ARIs in children in developing countries.
Currently, three Hib conjugate vaccines are available for use in infants and young children. The efficacy of Hib vaccine in preventing invasive diseases such as meningitis and pneumonia has been well documented in several studies in industrialized countries. All studies showed protective efficacy >90% against laboratory-confirmed invasive disease, irrespective of the choice of vaccine. Consequently, all industrialized countries include Hib vaccine in their national immunization programs, resulting in the virtual elimination of invasive Hib disease because of immunity in those vaccinated and a herd effect in those who are not vaccinated. The initial promise and consequent general perception was that Hib vaccine was to protect against meningitis, but in developing countries, the vaccine is likely to have a greater effect on preventing LRIs. The easily measured effect is on invasive disease, including bacteremic pneumonia. The vaccine probably has an effect on nonbacteremic pneumonia, but this effect is difficult to quantify because of the lack of an adequate method for establishing bacterial etiology.
Two kinds of vaccines are currently available against pneumococci: a 23-valent polysaccharide vaccine (23-PSV), which is more appropriate for adults than children, and a 7-valent protein-conjugated PSV. Studies of the efficacy of the PSV in preventing ARIs or ear infection in children in industrialized countries have shown conflicting results. The efficacy was more marked in children over 2 years of age than in younger children. The only studies evaluating the effect of the PSV in children in developing countries are a series of three trials conducted in Papua New Guinea. The analysis of the pooled data from these trials showed a 59% reduction in LRI mortality in children under five at the time of the vaccination and a 50% reduction in children under two. On the basis of these and other studies, the investigators concluded that the vaccine had an effect on severe pneumonia. In India, two pneumococcal vaccines are available for adults aged 18 and above, a pneumococcal PSV 23-valent (Pulmovax 23) with 23 serotypes and a pneumococcal conjugate vaccine 13-valent (Prevenar 13) with 13 serotypes. Both vaccines are intramuscular, and conjugated vaccine can also be administered subcutaneously.
Influenza is a serious disease that can lead to hospitalization and sometimes even death in children. Every flu season is different, and influenza infection can affect people differently. An annual seasonal flu vaccine (either the flu shot or the nasal spray flu vaccine) is the best way to reduce the chances that one can get seasonal flu and spread it to others. Flu vaccines cause antibodies to develop in the body about 2 weeks after vaccination. These antibodies provide protection against infection with the viruses that are in the vaccine. The seasonal flu vaccine protects against the influenza viruses that will be most common during the upcoming season. Traditional flu vaccines (called trivalent vaccines) are made to protect against three flu viruses; an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus. In addition, there are flu vaccines made to protect against four flu viruses (called “quadrivalent” vaccines). A flu vaccine is needed every season for two reasons. First, the body's immune response from vaccination declines over time, so an annual vaccine is needed for optimal protection. Second, because flu viruses are constantly changing, the formulation of the flu vaccine is reviewed each year and sometimes updated to keep up with changing flu viruses. Influenza vaccine effectiveness can vary from year to year and among different age and risk groups.
The influenza and pneumococcal vaccines can be given at the same time, preferably in different arms.
The simplification and systematization of case management for early diagnosis and treatment of ARIs have enabled significant reductions in mortality in developing countries, where access to pediatricians is limited. The WHO clinical guidelines for ARI case management use two key clinical signs: respiratory rate to distinguish children with pneumonia from those without and lower chest wall indrawing to identify severe pneumonia requiring referral and hospital admission. Children with audible stridor when calm and at rest or with such danger signs of severe disease as inability to feed also require referral. Children without these signs are classified as having an ARI, but not pneumonia. Children showing only rapid breathing are treated for pneumonia with outpatient antibiotic therapy. The choice of an antimicrobial drug for treatment is based on the well-established finding that most childhood bacterial pneumonias are caused by S. pneumoniae or H. influenzae. The emergence of antimicrobial resistance in S. pneumoniae and H. influenzae is a serious concern. In some settings, in vitro tests show that more than 50% of the respiratory isolates of both bacteria are resistant to co-trimoxazole, and penicillin resistance to S. pneumoniae is gradually becoming a problem worldwide.
| Conclusions|| |
The evidence clearly shows that the WHO case management approach and the wider use of available vaccines will reduce ARIs mortality among children by half to two-thirds. The systematic application of simplified case management alone, the cost of which is low enough to be affordable by almost any developing country, will reduce ARIs mortality by at least one-third. The urgent need is to translate this information into actual implementation. The international medical community is only beginning to appreciate the potential benefits of Hib, influenza, and pneumococcal vaccines. Nevertheless, it requires to be used continuously to evaluate the vaccines' cost-effectiveness in children population.
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