Epidemiology, etiology, x-ray features, importance of co-infections and clinical features of viral pneumonia in developing countries

Abstract

Pneumonia is still the number one killer of young children globally, accounting for 18% of mortality in children under 5 years of age. An estimated 120 million new cases of pneumonia occur globally each year. In developing countries, management and prevention efforts against pneumonia have traditionally focused on bacterial pathogens. More recently however, viral pathogens have gained attention as a result of improved diagnostic methods, such as polymerase chain reaction, outbreaks of severe disease caused by emerging pathogens, discovery of new respiratory viruses as well as the decrease in bacterial pneumonia as a consequence of the introduction of highly effective conjugate vaccines. Although the epidemiology, etiology and clinical characterization of viral infections are being studied extensively in the developed world, little data are available from low- and middle-income countries. In this paper, we review the epidemiology, etiology, clinical and radiological features of viral pneumonia in developing countries.

Keywords::

• acute respiratory infections
• adult
• children
• developing countries
• pneumonia
• viral

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Despite great reductions in child mortality over the last decade, pneumonia remains the major killer of young children globally, accounting for 18% of the under-5 mortality. In recent years, attention has shifted toward non-bacterial causes of pneumonia, and more specifically, to viral-attributable respiratory infections. Data of viral pneumonia from developing countries are scarce.

• In developed countries, the highest incidence of acute respiratory infections (ARIs) is evidenced among children younger than 5 years of age, falling dramatically after 15 years of age and increasing again among adults older than 75 years of age. The few available data from the developing world suggests similar age-distribution tendencies.

• When considering only the most comprehensive studies (detection by PCR of at least 10 viruses in study populations larger than 500 patients over a minimum 12-month period), the prevalence of viral infections in pediatric pneumonia cases ranged from 47 to 69%, with human rhinovirus, respiratory syncytial virus, influenza virus, adenovirus and human metapneumovirus being the most commonly detected pathogens. In adult pneumonia cases, human rhinovirus and influenza are the most frequently detected viruses.

• Causality cannot be inferred from a positive viral isolate in a respiratory sample, especially from upper respiratory tract samples, given lack of controls in most studies.

• Overlapping clinical and radiological presentation is common in viral pneumonia cases caused by different respiratory virus, and more importantly, viral pneumonia signs and symptoms seem to overlap with those of bacterial pneumonia.

• Serum biomarkers used in developed countries to distinguish between viral and bacterial infection such as procalcitonin and C-reactive protein increase in patients with malaria infection compromising their utility in malaria-endemic settings.

• There are no registered vaccines against respiratory viruses suitable for use in children younger than 6 months of age, which is the population at highest risk.