The endoplasmic reticulum (ER) is the site of lipid biosynthesis and secretory protein folding, which must be adjusted to accommodate the physiological needs and stresses of the cell. Since ER cannot be made de novo, it must be inherited faithfully. During decreased ER function cortical ER and cell cycle progression are delayed by the ER surveillance (ERSU) pathway, which is mediated by the MAP kinase Slt2. We have identified the mechanism through which the accumulation of unfolded proteins, ER stress, activates Slt2. This response is separate from the canonical ER stress response, the unfolded protein response (UPR). Furthermore, this mechanism is distinct from the cell wall integrity (CWI) pathway, the canonical Slt2 activation pathway. Activated Slt2 has many cytoplasmic and nuclear targets, including the transcription factor Rlm1. We find that Rlm1 aids in cell survival during conditions of decreased ER function, but does not play a role in the ERSU pathway

Objective

To describe the pattern of transmission of severe acute respiratory coronavirus virus 2 (SARS-CoV-2) during 2 nosocomial outbreaks of coronavirus disease 2019 (COVID-19) with regard to the possibility of airborne transmission.

Design

Contact investigations with active case finding were used to assess the pattern of spread from 2 COVID-19 index patients.

Setting

A community hospital and university medical center in the United States, in February and March, 2020, early in the COVID-19 pandemic.

Patients

Two index patients and 421 exposed healthcare workers.

Methods

Exposed healthcare workers (HCWs) were identified by analyzing the electronic medical record (EMR) and conducting active case finding in combination with structured interviews. Healthcare coworkers (HCWs) were tested for COVID-19 by obtaining oropharyngeal/nasopharyngeal specimens, and RT-PCR testing was used to detect SARS-CoV-2.

Results

Two separate index patients were admitted in February and March 2020, without initial suspicion for COVID-19 and without contact or droplet precautions in place; both patients underwent several aerosol-generating procedures in this context. In total, 421 HCWs were exposed in total, and the results of the case contact investigations identified 8 secondary infections in HCWs. In all 8 cases, the HCWs had close contact with the index patients without sufficient personal protective equipment. Importantly, despite multiple aerosol-generating procedures, there was no evidence of airborne transmission.

Conclusion

These observations suggest that, at least in a healthcare setting, most SARS-CoV-2 transmission is likely to take place during close contact with infected patients through respiratory droplets, rather than by long-distance airborne transmission.