Introduction
Respiratory viruses are a leading cause of morbidity and mortality among children and adults worldwide 1, 2. The burden of respiratory viruses is disproportionately high in low-to-middle income countries (LMICs) 3, 4. Specific respiratory virus infections (RVIs), such as influenza and respiratory syncytial virus (RSV), and more recently SARS-CoV-2, are the major contributors to this high burden of disease 3, 4, 5. In 2018, influenza virus accounted for 870,000 influenza-virus-associated hospital admissions, 15,300 in-hospital deaths, and around 34,800 overall influenza-virus-associated acute lower respiratory infections (ALRI) deaths among children under 5 years of age 6. Around 82% of in-hospital deaths due to influenza virus occurred in low-income countries (LICs) and LMICs 6. Whereas, it is estimated that RSV accounts for 33 million cases and 118,000 deaths annually in children under five, of which 22 million cases and 103,000 deaths are in LICs and LMICs 7. In addition to the annual impact of common respiratory viruses like influenza and RSV, emerging respiratory viruses such as avian influenza A (H5N1) virus, influenza A(H1N1) pdm09 virus, MERS-CoV, avian influenza A(H7N9), and most recently, SARS-CoV-2 represent elevated threats to global health security 1, 8. Collectively these viruses markedly contribute to respiratory disease morbidity and mortality in populous countries like Indonesia9, 10, 11.
Indonesia is a tropical archipelago of islands with high humidity and a population of around 271 million 12. Indonesia has year-round respiratory virus activity with seasonal peaks ranging between October and April, which corresponds with the wet and dry seasons 13. More recent surveillance efforts have shown dominant seasonal influenza activity occurring December through February with clear patterns of phased infections among the different seasonal influenza virus strains (influenza A/pH1, influenza A/H3, and influenza B) 10, 14. Far less is known about the epidemiology and burden of RSV and other respiratory viral infections in Indonesia as comprehensive surveillance for non-influenza viruses is limited. Indonesia also has a growing population of animal reservoirs for zoonotic infections including poultry, rodents, wild birds, dogs, pigs, and monkeys 15. Given that Indonesia is an LMIC with a large and diverse population, the risk of viral respiratory disease burden is high. Therefore, this literature review was conducted to better understand the epidemiology of viral respiratory disease in Indonesia.