Pathogens Causing Respiratory Tract Infections in Children Less Than 5 Years of Age in Senegal

Knobbe, Rebecca B; Diallo, Abdallah; Fall, Amary; Gueye, Aida D; Dieng, Assane; van Immerzeel, Tabitha D; Ba, Abou; Diop, Amadou; Diop, Abdoulaye; Niang, Mbayame; Boye, Cheikh SB

Worldwide, the leading cause of paediatric mortality and morbidity in the postneonatal period remains lower respiratory tract infections (LRTIs). The WHO (World Health Organization) estimated that more than 800 000 of the 5.6 million total deaths in children less than 5 years old were caused by LRTIs in 2016. 1 A meta-analysis found a hospital-based case-fatality ratio of 6.1% in children in lowincome countries with severe LRTI, compared with 3.9% in high-income countries. 2 Children with LRTI can present with a highly variable package of symptoms including cough, tachypnoea, dyspnoea, fever, rhinitis, chest pain, abdominal pain, vomiting, diarrhoea, headache and lethargy. The WHO guidelines states tachypnoea as the main diagnostic criterion for pneumonia requiring an antibiotic. 3 However, distinction from upper airway infections and other illnesses such as asthma/bronchiolitis, anaemia or malaria can be challenging when minimal diagnostic tools are available. 4 Furthermore, in many low-and middle-income countries, treatment policies are empiric or based on foreign guidelines, due to a lack of local causal studies. 5 These could be reasons why research has discovered an overdiagnosis and overprescription of antibiotics to treat pneumonia in low-income countries. 6 One of the biggest public health problems of this century is antimicrobial resistance. It threatens the effective treatment of major infections and is induced by an overuse and inappropriate usage of antibiotics. 7 This phenomena has major consequences: higher health-related costs because of the necessity of more expensive antibiotics, rising mortality rates due to Pathogens Causing Respiratory Tract Infections in Children Less Than 5 Years of Age in Senegal 2 Microbiology Insights untreatable infections and an increasing danger for the immunosuppressed patient. 7, 8 Moreover, viral causes of LRTIs have become seemingly more important. 9 Ancient studies in mostly Western countries frequently described Haemophilus influenza B (Hib), Streptococcus pneumoniae, and Moraxella catarrhalis as major causative pathogens of LRTIs. 10, 11 Nonetheless, while in 2000, S pneumoniae was responsible for 600 000 deaths in children, in 2015, this number dropped to 294 000 children. 12 Recent developments, such as the implementation of the pneumococcal conjugate vaccine and the Hib vaccine, are responsible for a reduction in the burden of these respiratory bacteria but may also have induced a shift in the pathogens causing LRTIs. 9, 13 Recent research in Senegal indicated viruses as main pathogens of all acute respiratory tract infections (ARTIs), both upper and lower. The frequency of virus detection was even higher than those found in several other countries. 14,15 Viruses most commonly found in Senegal were respiratory syncytial virus (RSV ), adenovirus, rhinovirus, influenza virus A, enterovirus, human bocavirus, and parainfluenza viruses. 16 Furthermore, there are indications that nowadays ARTIs are more often caused by the sequential or concurrent interaction of different pathogens and that the presence of multiple organisms is linked with the existence of a LRTI and with severity of disease. 17, 18 To reduce paediatric mortality caused by LRTI, while fighting antibiotic resistance, more knowledge about the cause of respiratory infections, especially in low-and middle-income countries, is essential. Case-control studies have been conducted in Africa, investigating the association between