Central Nervous System Viral Diseases; Enterovirus D, Human/pathogenicity; Enterovirus Infections; Epidemics/prevention & control; Muscle Weakness; Myelitis; Neuromuscular Diseases; Viral Vaccines; Central Nervous System Viral Diseases/complications; Central Nervous System Viral Diseases/epidemiology; Central Nervous System Viral Diseases/prevention & control; Central Nervous System Viral Diseases/virology; Child, Preschool; Enterovirus Infections/complications; Enterovirus Infections/epidemiology; Enterovirus Infections/prevention & control; Enterovirus Infections/virology; Humans; Muscle Weakness/epidemiology; Muscle Weakness/etiology; Muscle Weakness/prevention & control; Muscle Weakness/virology; Myelitis/complications; Myelitis/epidemiology; Myelitis/prevention & control; Myelitis/virology; Neuromuscular Diseases/complications; Neuromuscular Diseases/epidemiology; Neuromuscular Diseases/prevention & control; Neuromuscular Diseases/virology