Six years have passed since the outbreak of severe acute respiratory syndrome (SARS). Previous studies indicated that specific Abs to SARS-related coronavirus (SARS-CoV) waned over time in recovered SARS patients. It is critical to find out whether a potential anamnestic response, as seen with other viral infections, exists to protect a person from reinfection in case of another SARS outbreak. Recovered SARS patients were followed up to 6 y to estimate the longevity of specific Ab. The specific memory B cell and T cell responses to SARS-CoV Ags were measured by means of ELISPOT assay. Factors in relation to humoral and cellular immunity were investigated. Six years postinfection, specific IgG Ab to SARS-CoV became undetectable in 21 of the 23 former patients. No SARS-CoV Ag-specific memory B cell response was detected in either 23 former SARS patients or 22 close contacts of SARS patients. Memory T cell responses to a pool of SARS-CoV S peptides were identified in 14 of 23 (60.9%) recovered SARS patients, whereas there was no such specific response in either close contacts or healthy controls. Patients with more severe clinical manifestations seemed to present a higher level of Ag-specific memory T cell response. SARS-specific IgG Ab may eventually vanish and peripheral memory B cell responses are undetectable in recovered SARS patients. In contrast, specific T cell anamnestic responses can be maintained for at least 6 y. These findings have applications in preparation for the possible reemergence of SARS.

The emergence of two variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) — B.1.1.7 in the United Kingdom and B.1.351 in South Africa — has aroused concern that these variants may escape immunity resulting from either previous infection or vaccination. In an attempt to measure the resistance of these variants to neutralization elicited by infection or vaccination, we generated recombinant vesicular stomatitis virus–based SARS-CoV-2 pseudoviruses containing the spike protein of the Wuhan-1 reference strain (wild-type), the D614G mutation, and the B.1.1.7 and B.1.351 variants. (Details regarding the recombination process are provided in the Supplementary Appendix, available with the full text of this letter at NEJM.org.)

Significance: Since the initial recognition of Ebola virus disease (EVD) in 1976, many epidemics have occurred in Africa. Serious concerns remain that the fatal disease may repeatedly reemerge. In this study, we used data from an unprecedented EVD outbreak in Sierra Leone to map spatiotemporal transmission patterns, identify influential factors, and assess the effects of interventions at the chiefdom level. Furthermore, we have quantified household transmissibility and the temporal association between interventions and household transmission. Our findings have deepened the understanding of the transmission dynamics of EVD and provided key information for future modeling efforts in forecasting future epidemics and establishing intervention strategies.

We investigated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) environmental contamination in 2 rooms of a quarantine hotel after 2 presymptomatic persons who stayed there were laboratory-confirmed as having coronavirus disease. We detected SARS-CoV-2 RNA on 8 (36%) of 22 surfaces, as well as on the pillow cover, sheet, and duvet cover.

Data concerning the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in asymptomatic and paucisymptomatic patients are lacking. We report a 3-family cluster of infections involving asymptomatic and paucisymptomatic transmission. Eight of 15 (53%) members from 3 families were confirmed with SARS-CoV-2 infection. Of 8 patients, 3 were asymptomatic and 1 was paucisymptomatic. An asymptomatic mother transmitted the virus to her son, and a paucisymptomatic father transmitted the virus to his 3-month-old daughter. SARS-CoV-2 was detected in the environment of 1 household. The complete genomes of SARS-CoV-2 from the patients were > 99.9% identical and were clustered with other SARS-CoV-2 sequences reported from China and other countries.