Acute flaccid myelitis (AFM), a serious paralytic illness, was first recognized as a distinct condition in 2014, when cases were reported concurrent with a large U.S. outbreak of severe respiratory ...illness caused by enterovirus D-68 (EV-D68). Since 2014, nationwide outbreaks of AFM have occurred every 2 years in the United States; the cause for the recent change in the epidemiology of AFM in the United States, including the occurrence of outbreaks and a biennial periodicity since 2014, is under investigation. This report updates clinical, laboratory, and outcome data for cases reported to CDC during 2018.
Clinical data and specimens from persons in the United States who met the clinical criterion for AFM (acute onset of flaccid limb weakness) with onset in 2018 were submitted to CDC for classification of the illnesses as confirmed, probable, or non-AFM cases. Enterovirus/rhinovirus (EV/RV) testing was performed on available specimens from persons meeting the clinical criterion. Descriptive analyses, laboratory results, and indicators of early recognition and reporting are summarized.
From January through December 2018, among 374 reported cases of AFM, 233 (62%) (from 41 states) were classified as confirmed, 26 (7%) as probable, and 115 (31%) as non-AFM cases. Median ages of patients with confirmed, probable, and non-AFM cases were 5.3, 2.9, and 8.8 years, respectively. Laboratory testing identified multiple EV/RV types, primarily in respiratory and stool specimens, in 44% of confirmed cases. Among confirmed cases, the interval from onset of limb weakness until specimen collection ranged from 2 to 7 days, depending on specimen type. Interval from onset of limb weakness until reporting to CDC during 2018 ranged from 18 to 36 days, with confirmed and probable cases reported earlier than non-AFM cases.
Identification of risk factors leading to outbreaks of AFM remains a public health priority. Prompt recognition of signs and symptoms, early specimen collection, and complete and rapid reporting will expedite public health investigations and research studies to elucidate the recent epidemiology of AFM and subsequently inform treatment and prevention recommendations.
The cellular localization of the Thy-1 antigen during development of the chick cerebellum has been investigated using a monoclonal antibody SB1-20.11. Improved cellular morphology and retention of ...both membrane and intracellular antigenicity was achieved by the immunohistochemical labelling of polyester wax sections using an indirect peroxidase visualization protocol. A parallel histological investigation was carried out using a modified silver staining procedure based on that of Bodian. Immunoreactivity was found throughout development in the soma and dendritic tree of the Purkinje cell, in the internal granular layer, white matter and elements of the deep cerebellar nuclei. The antigen's expression closely correlates to the morphological maturation of Purkinje cell population. Furthermore, it appears to reflect the formation of glomeruli and the basket cell interaction with the Purkinje cell. An association of Thy-1 with climbing fibres, as reported previously in rodent species, cannot be unambiguously shown in the chick because of the high levels of Thy-1 expressed throughout development on the Purkinje cell dendrites in the molecular layer. The spatial and temporal pattern of expression in the chick cerebellum suggests that Thy-1 contributes to the definition of synaptic fields.
The cellular localization of Thy-1 in the chick retina was investigated by selectively destroying certain populations of neurons with toxins. In control retinae four weeks after intravitreal ...injection of vehicle, there was strong immunoreactivity for Thy-1 in the nerve fibre layer, ganglion cell layer and inner plexiform layer. By contrast, 4 weeks after intraocular injection with 1.25 nmol of colchicine, virtually all ganglion cells had been destroyed, but most amacrine cells remained. Very little Thy-1 immunoreactivity was evident in these retinae. Four weeks after intraocular injection of 2 mumol of N-methyl-D-aspartic acid (NMDA), a large proportion of amacrine cells had been destroyed, but most ganglion cells remained. In these retinae Thy-1 immunoreactivity was present in the nerve fibre, ganglion cell and inner plexiform layers, in the latter with greater intensity than in controls. We conclude that in chicks the Thy-1 antigen is principally, if not exclusively restricted to ganglion cells.
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