ACE2	Angiotensin-converting enzyme 2
ADP	Adenosine diphosphate
AISI	Aggregate index of systemic inflammation
AKI	Acute kidney injury
ALRTI	Acute lower respiratory tract infection
ARDS	Acute respiratory distress syndrome
AUC	Area under the curve
BLR	Basophil-to-lymphocyte ratio
BP	Bordetella pertussis
cAMP	Cyclic adenosine monophosphate
CAP	Community-acquired pneumonia
CARDS	Community-acquired respiratory distress syndrome
CBC	Complete blood count
CCL2	C-C motif chemokine ligand 2
CD4	Cluster of differentiation 4
CD8	Cluster of differentiation 8
CI	Confidence interval
COVID-19	Coronavirus disease 2019
CRP	C-reactive protein
CXCL10	C-X-C motif chemokine ligand 10
CXCL8	C-X-C motif chemokine ligand 8
CXR	Chest X-ray
DNA	Deoxyribonucleic acid
dNLR	Derived neutrophil-to-lymphocyte ratio
EBV	Epstein–Barr virus
ELR	Eosinophil-to-lymphocyte ratio
EMR	Eosinophil-to-monocyte ratio
H1N1	Influenza A virus subtype H1N1
H3N2	Influenza A virus subtype H3N2
HAdV	Human adenovirus
HAP	Hospital-acquired pneumonia
HC	Healthy control
HIV	Human immunodeficiency virus
HMPV	Human metapneumovirus
HPIV	Human parainfluenza virus
HR	Hazard ratio
ICU	Intensive care unit
IFN-α	Interferon alpha
IFN-β	Interferon beta
IFN-γ	Interferon gamma
IGRA	Interferon-gamma release assay
IL-1β	Interleukin-1 beta
IL-33	Interleukin-33
IL-6	Interleukin-6
IL-8	Interleukin-8
InfA	Influenza A
InfB	Influenza B
IQR	Interquartile range
IRF3	Interferon regulatory factor 3
IRF7	Interferon regulatory factor 7
LMR	Lymphocyte-to-monocyte ratio
LNR	Lymphocyte-to-neutrophil ratio
LOS	Length of stay
LPR	Lymphocyte-to-platelet ratio
LRTI	Lower respiratory tract infection
LUS	Lung ultrasound
LYM*PLT	Lymphocyte multiplied by platelet
MBI	Mixed bacterial infection
MLR	Monocyte-to-lymphocyte ratio
MP	Mycoplasma pneumoniae
MPI	Mixed pathogen infection
MPP	Mycoplasma pneumoniae pneumonia
MPVLR	Mean platelet volume-to-lymphocyte ratio
MPV/PLT	Mean platelet volume-to-platelet count
MTB	Mycobacterium tuberculosis
MVI	Mixed viral infection
MyD88	Myeloid differentiation primary response 88
NEUT%	Neutrophil percentage
NF-κB	Nuclear factor kappa B
NK	Natural killer
NLPR	Neutrophil-to-lymphocyte-platelet ratio
NLR	Neutrophil-to-lymphocyte ratio
NMLR	Neutrophil-monocyte-to-lymphocyte ratio
NMR	Neutrophil-to-monocyte ratio
NP	Necrotizing pneumonia
NPR	Neutrophil-to-platelet ratio
NPV	Negative predictive value
OM	Otitis media
OR	Odds ratio
PB	Plastic bronchitis
PCR	Polymerase chain reaction
PCT	Procalcitonin
PICU	Pediatric intensive care unit
PLR	Platelet-to-lymphocyte ratio
PNR	Platelet-to-neutrophil ratio
PPV	Positive predictive value
PRESS	Pediatric respiratory severity score
RBC	Red blood cell
RMPP	Refractory Mycoplasma pneumoniae pneumonia
RNA	Ribonucleic acid
RR	Relative risk
RSV	Respiratory syncytial virus
RT-PCR	Reverse transcription polymerase chain reaction
SAA	Serum amyloid A
SARS-CoV-2	Severe acute respiratory syndrome coronavirus 2
SC2	SARS-CoV-2
SII	Systemic immune-inflammation index
SIRI	Systemic inflammatory response index
SMPP	Severe Mycoplasma pneumoniae pneumonia
SP	Streptococcus pneumoniae
SPP	Streptococcus pneumoniae pneumonia
TB	Tuberculosis
Th2	T helper type 2
TLR2	Toll-like receptor 2
TMPRSS2	Transmembrane serine protease 2
TNF-α	Tumor necrosis factor alpha
URTI	Upper respiratory tract infection
VP	Viral pneumonia
WBC	White blood cell
YKL-40	Chitinase-3-like protein 1