IMPORTANCE: Reported cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection likely underestimate the prevalence of infection in affected communities. Large-scale seroprevalence studies provide better estimates of the proportion of the population previously infected. OBJECTIVE: To estimate prevalence of SARS-CoV-2 antibodies in convenience samples from several geographic sites in the US. DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional study performed serologic testing on a convenience sample of residual sera obtained from persons of all ages. The serum was collected from March 23 through May 12, 2020, for routine clinical testing by 2 commercial laboratory companies. Sites of collection were San Francisco Bay area, California; Connecticut; south Florida; Louisiana; Minneapolis-St Paul-St Cloud metro area, Minnesota; Missouri; New York City metro area, New York; Philadelphia metro area, Pennsylvania; Utah; and western Washington State. EXPOSURES: Infection with SARS-CoV-2. MAIN OUTCOMES AND MEASURES: The presence of antibodies to SARS-CoV-2 spike protein was estimated using an enzyme-linked immunosorbent assay, and estimates were standardized to the site populations by age and sex. Estimates were adjusted for test performance characteristics (96.0% sensitivity and 99.3% specificity). The number of infections in each site was estimated by extrapolating seroprevalence to site populations; estimated infections were compared with the number of reported coronavirus disease 2019 (COVID-19) cases as of last specimen collection date. RESULTS: Serum samples were tested from 16 025 persons, 8853 (55.2%) of whom were women; 1205 (7.5%) were 18 years or younger and 5845 (36.2%) were 65 years or older. Most specimens from each site had no evidence of antibodies to SARS-CoV-2. Adjusted estimates of the proportion of persons seroreactive to the SARS-CoV-2 spike protein antibodies ranged from 1.0% in the San Francisco Bay area (collected April 23-27) to 6.9% of persons in New York City (collected March 23-April 1). The estimated number of infections ranged from 6 to 24 times the number of reported cases; for 7 sites (Connecticut, Florida, Louisiana, Missouri, New York City metro area, Utah, and western Washington State), an estimated greater than 10 times more SARS-CoV-2 infections occurred than the number of reported cases. CONCLUSIONS AND RELEVANCE: During March to early May 2020, most persons in 10 diverse geographic sites in the US had not been infected with SARS-CoV-2 virus. The estimated number of infections, however, was much greater than the number of reported cases in all sites. The findings may reflect the number of persons who had mild or no illness or who did not seek medical care or undergo testing but who still may have contributed to ongoing virus transmission in the population.

Since emergence of SARS-CoV-2 in late 2019, there has been a critical need to understand prevalence, transmission patterns, to calculate the burden of disease and case fatality rates. Molecular diagnostics, the gold standard for identifying viremic cases, are not ideal for determining true case counts and rates of asymptomatic infection. Serological detection of SARS-CoV-2 specific antibodies can contribute to filling these knowledge gaps. In this study, we describe optimization and validation of a SARS-CoV-2-specific-enzyme linked immunosorbent assay (ELISA) using the prefusion-stabilized form of the spike protein [1]. We performed receiver operator characteristic (ROC) analyses to define the specificities and sensitivities of the optimized assay and examined cross reactivity with immune sera from persons confirmed tohave had infections with other coronaviruses. These assays will be used to perform contact investigations and to conduct large-scale, cross sectional surveillance to define disease burden in the population.

BACKGROUND: During 2017, a multi-state outbreak investigation occurred following the confirmation of Seoul virus (SEOV) infections in people and pet rats. A total of 147 humans and 897 rats were tested. METHODS: In addition to IgG and IgM serology and traditional RT-PCR, novel quantitative RT-PCR primers/probe were developed, and whole genome sequencing was performed. RESULTS: Seventeen people had SEOV IgM, indicating recent infection; seven reported symptoms and three were hospitalized. All patients recovered. Thirty-one facilities in 11 US states had SEOV infection, and among those with >/=10 rats tested, rat IgG prevalence ranged 2-70% and SEOV RT-PCR positivity ranged 0-70%. Human lab-confirmed cases were significantly associated with rat IgG positivity and RT-PCR positivity (p=0.03 and p=0.006, respectively). Genomic sequencing identified >99.5% homology between SEOV sequences in this outbreak, and these were >99% identical to SEOV associated with previous pet rat infections in England, the Netherlands, and France. Frequent trade of rats between home-based ratteries contributed to transmission of SEOV between facilities. CONCLUSIONS: Pet rat owners, breeders, and the healthcare and public health community should be aware and take steps to prevent SEOV transmission in pet rats and to humans. Biosecurity measures and diagnostic testing can prevent further infections.

During the Ebola virus outbreak of 2013-2016, the Viral Special Pathogens Branch field laboratory in Sierra Leone tested approximately 26 000 specimens between August 2014 and October 2015. Analysis of the B2M endogenous control Ct values showed its utility in monitoring specimen quality, comparing results with different specimen types, and interpretation of results. For live patients, blood is the most sensitive specimen type and oral swabs have little diagnostic utility. However, swabs are highly sensitive for diagnostic testing of corpses.

Host cell kinases are important for the replication of a number of hemorrhagic fever viruses. We tested a panel of kinase inhibitors for their ability to block the replication of multiple hemorrhagic fever viruses. OSU-03012 inhibited the replication of Lassa, Ebola, Marburg and Nipah viruses, whereas BIBX 1382 dihydrochloride inhibited Lassa, Ebola and Marburg viruses. BIBX 1382 blocked both Lassa and Ebola virus glycoprotein-dependent cell entry. These compounds may be used as tools to understand conserved virus-host interactions, and implicate host cell kinases that may be targets for broad spectrum therapeutic intervention.

Andes virus (ANDV) is the most common causative agent of hantavirus pulmonary syndrome (HPS) in the Americas, and is the only hantavirus associated with human-to-human transmission. Case fatality rates of ANDV-induced HPS are approximately 40%. There are currently no effective vaccines or antivirals against ANDV. Since HPS severity correlates with viral load, we tested small interfering RNA (siRNA) directed against ANDV genes as a potential antiviral strategy. We designed pools of 4 siRNAs targeting each of the ANDV genome segments (S, M, and L), and tested their efficacy in reducing viral replication in vitro. The siRNA pool targeting the S segment reduced viral transcription and replication in Vero-E6 cells more efficiently than those targeting the M and L segments. In contrast, siRNAs targeting the S, M, or L segment were similar in their ability to reduce viral replication in human lung microvascular endothelial cells. Importantly, these siRNAs inhibit ANDV replication even if given after infection. Taken together, our findings indicate that siRNAs targeting the ANDV genome efficiently inhibit ANDV replication, and show promise as a strategy for developing therapeutics against ANDV infection.