Evidence for Limited Early Spread of COVID-19 Within the United States, January-February 2020.

From January 21 through February 23, 2020, public health agencies detected 14 U.S. cases of coronavirus disease 2019 (COVID-19), all related to travel from China (1,2). The first nontravel-related U.S. case was confirmed on February 26 in a California resident who had become ill on February 13 (3). Two days later, on February 28, a second nontravel-related case was confirmed in the state of Washington (4,5). Examination of four lines of evidence provides insight into the timing of introduction and early transmission of SARS-CoV-2, the virus that causes COVID-19, into the United States before the detection of these two cases. First, syndromic surveillance based on emergency department records from counties affected early by the pandemic did not show an increase in visits for COVID-19-like illness before February 28. Second, retrospective SARS-CoV-2 testing of approximately 11,000 respiratory specimens from several U.S. locations beginning January 1 identified no positive results before February 20. Third, analysis of viral RNA sequences from early cases suggested that a single lineage of virus imported directly or indirectly from China began circulating in the United States between January 18 and February 9, followed by several SARS-CoV-2 importations from Europe. Finally, the occurrence of three cases, one in a California resident who died on February 6, a second in another resident of the same county who died February 17, and a third in an unidentified passenger or crew member aboard a Pacific cruise ship that left San Francisco on February 11, confirms cryptic circulation of the virus by early February. These data indicate that sustained, community transmission had begun before detection of the first two nontravel-related U.S. cases, likely resulting from the importation of a single lineage of virus from China in late January or early February, followed by several importations from Europe. The widespread emergence of COVID-19 throughout the United States after February highlights the importance of robust public health systems to respond rapidly to emerging infectious threats.

Completeness of reporting of rabies postexposure prophylaxis in King County, Washington.

The completeness of rabies postexposure prophylaxis (PEP) reporting was evaluated in King County, Washington State. Information on rabies immune globulin prescriptions was obtained from hospital pharmacies associated with emergency departments in King County from 2003 to June 2006. Rabies immune globulin is given at the initiation of rabies PEP which is usually started at emergency departments. Because pharmacies are not regular sources of rabies PEP reporting, we compared pharmacy cases with cases reported via routine passive surveillance methods. A capture-recapture method was used to calculate the estimated number of unreported cases from all sources. Reporting completeness was calculated by dividing the number of cases reported via routine surveillance with the sum of reported and estimated unreported cases. Seventy-one unreported rabies PEP cases were identified by comparing previously reported cases with pharmacy cases. A total of 128 cases were estimated to have been missed by the surveillance system. Overall reporting completeness was 62 percent increasing to almost 80 percent in 2005 and 2006. Our findings illustrate the importance of evaluating surveillance systems and suggest that it may be useful to institute active rabies PEP surveillance with emergency departments in addition to continuing educating healthcare providers and facilities about reporting.

ASIC1a-specific modulation of acid-sensing ion channels in mouse cortical neurons by redox reagents.

Acid-sensing ion channel (ASIC)-1a, the major ASIC subunit with Ca2+ permeability, is highly expressed in the neurons of CNS. Activation of these channels with resultant intracellular Ca2+ accumulation plays a critical role in normal synaptic plasticity, learning/memory, and in acidosis-mediated glutamate receptor-independent neuronal injury. Here we demonstrate that the activities of ASICs in CNS neurons are tightly regulated by the redox state of the channels and that the modulation is ASIC1a subunit dependent. In cultured mouse cortical neurons, application of the reducing agents dramatically potentiated, whereas the oxidizing agents inhibited the ASIC currents. However, in neurons from the ASIC1 knock-out mice, neither oxidizing agents nor reducing reagents had any effect on the acid-activated current. In Chinese Hamster Ovary cells, redox-modifying agents only affected the current mediated by homomeric ASIC1a, but not homomeric ASIC1b, ASIC2a, or ASIC3. In current-clamp recordings and Ca(2+)-imaging experiments, the reducing agents increased but the oxidizing agents decreased acid-induced membrane depolarization and the intracellular Ca2+ accumulation. Site-directed mutagenesis studies identified involvement of cysteine 61 and lysine 133, located in the extracellular domain of the ASIC1a subunit, in the modulation of ASICs by oxidizing and reducing agents, respectively. Our results suggest that redox state of the ASIC1a subunit is an important factor in determining the overall physiological function and the pathological role of ASICs in the CNS.

Electrophysiological properties of mouse cortical neuron progenitors differentiated in vitro and in vivo.

Central neurons are highly vulnerable to injury and have limited ability to regenerate. Therefore, transplantation of exogenous neuronal progenitor cells has been considered a potential therapy for the restoration of lost neurons and associated brain function. In a previous study, we found that when injected into rat brain following focal ischemia, cortical neuronal progenitor cells cultured from mouse brain can migrate into ischemic areas and differentiate into cells with morphological and biochemical features of neurons. However, no direct electrophysiological evidence was provided to indicate that these cells become functional neurons in vivo.In this study, we measured the electrophysiological properties of neuronal progenitor cells from embryonic mouse cerebral cortex, both in cell culture and in rat brain slices following intracerebral injection. We demonstrate that some of these cells differentiate to express electrophysiological properties expected of mature neurons, including tetrodotoxin-sensitive Na(+) channels and N-methyl-D-aspartate receptor channels. These results support the feasibility of cell-replacement therapy for stroke using exogenous neuronal progenitors.

The presence of a conjugative Gram-positive Tn2009 in Gram-negative commensal bacteria.

OBJECTIVES: To determine whether mef(A)-msr(D) and tet(M) genes are linked in representative Gram-negative isolates and/or transferred together during conjugation. To molecularly characterize the Acinetobacter junii element and compare the structure and sequence with the non-conjugative Streptococcus pneumoniae Tn2009 element. METHODS: PCR assays, DNA-DNA hybridization and sequencing of PCR products were used. Nucleotide sequences were determined at the integration site of the mef(A) element into Tn916 and upstream and downstream flanking regions of the element. RESULTS: A total of 10 mef(A)-msr(D)- and tet(M)-positive isolates carried conjugative element(s). The A. junii Tn2009 element was indistinguishable from S. pneumoniae Tn2009. The region upstream of the A. junii Tn2009 contained an orf that was 89-91% identical to an S. pneumoniae spr1206 gene found upstream of the streptococcal Tn2009. In the A. junii, the spr1206 gene was separated by 67 bp from the end of the Tn2009, while 29 bp were found separating spr1206 from the streptococcal Tn2009. The 1201 bp downstream A. junii sequences included 913 unique sequences. CONCLUSIONS: A total of 10 different Gram-negative genera were found to carry the tet(M) genes, including the first description in three genera (Citrobacter, Proteus and Stenotrophomonas). All isolates were able to transfer the genes into > or =1 recipient with macrolide selection. Over 3000 bp were sequenced on each side of the insertion mef junction region in the A. junii and were indistinguishable from the streptococcal Tn2009. The A. junii Tn2009 element was flanked by an S. pneumoniae gene upstream and a unique sequence downstream, suggesting that the A. junii Tn2009 could be part of a larger element.

Staphylococcus efflux msr(A) gene characterized in Streptococcus, Enterococcus, Corynebacterium, and Pseudomonas isolates.

The staphylococcal msr(A) gene, coding for a macrolide efflux protein, was identified in three new gram-positive genera and one gram-negative genus. These msr(A) genes shared 99 to 100% identity with each other and the staphylococcal gene. This study demonstrates that the msr(A) gene has a wider host range than previously reported.