One month after the World Health Organization announced that the COVID-19 outbreak was a global pandemic on March 11, 2020, a state of emergency was declared on April 7 by the Prime Minister in Japan. We admitted all severe COVID-19 patients as the only designated institution for COVID-19 patients in Kobe. The number of patients in the hospital rapidly increased early in April 2020, and presumed nosocomial infection subsequently occurred, resulting in seven patients and 28 health-care workers being infected with SARS-CoV-2. We decided to suspend elective surgeries on April 20, closed the emergency department, arranged specific hospital zones, organized COVID-specific teams, set screening stations at all the entrances, and reduced staff–staff contact. Some of these practices had previously been introduced in a Taiwanese hospital and were successful in controlling the situation . These measures also appeared to be effective at our institution, and the number of transmissions to health-care workers decreased in the middle of April.
Once a hospital has an outbreak, it is a great challenge to resume medical practice. However, we decided to resume elective surgeries as a tertiary care medical center as of May 11 after a 3-week suspension. Presymptomatic COVID-19 patients can develop COVID-19 pneumonia postoperatively, leading to high mortality. An international, multicenter, cohort study reported a mortality rate of approximately 20% (53 deaths among 280 cases) in elective cases with perioperative SARS-CoV-2 infection , which is consistent with an early report from Wuhan, China .
There was also a concern about nosocomial infection from presymptomatic or asymptomatic COVID-19 patients following admission to hospital [11-13]. A preliminary study investigating seroprevalence demonstrated that IgG for SARS-CoV-2 was detected in 3.3% of the preserved sera of randomly selected outpatients who visited our hospital for reasons other than COVID-19 from March 31 to April 17, indicating that Kobe had significant transmissions of SARS-CoV-2 infections despite the limited number of cases confirmed by RT-PCR . Although the reliability of the kit used in the study still has to be determined, this finding also justified a strict screening of patients awaiting surgeries at that time. Thus, we proposed a seemingly strict screening system before hospital admission for elective surgeries.
First, we implemented RT-PCR testing, which has been widely recommended to confirm COVID-19-positive cases [15, 16], despite its sensitivity being 70% at the highest . The low sensitivity could be due to the timing of testing  or inadequate sampling methods. The timing of sampling was determined to be the day before admission as the most recent test results were considered to be the most reliable. Nasopharyngeal swab samples were obtained by otolaryngologists to ensure the quality of the samples. We also added chest CT imaging, which strengthens the screening results . While imaging studies are not routinely indicated as a screening test in asymptomatic individuals , in asymptomatic COVID-19-positive patients, pneumonic changes were frequently observed on CT images in patients quarantined on the “Diamond Princess” cruise ship .
What remains is the concern that some asymptomatic or presymptomatic patients could be admitted even after negative RT-PCR testing and CT as false negatives. An interview interrogating history of travel to or residence in areas where COVID-19 was prevalent or following contact with COVID-19 confirmed or suspected individuals was also conducted, although infection routes were unknown in approximately half of COVID-19 patients in Kobe at that time. Symptoms during 2 weeks prior to admission were recorded and checked, including fever, cough, throat pain, anosmia, and dysgeusia. However, we also considered that in the cohort from the “Diamond Princess” cruise ship and Japanese citizens evacuated from Wuhan, the estimated asymptomatic proportion was 17.9% and 33.3%, respectively [22, 23]. Considering that the incubation period is usually 4–7 days [24, 25] and that some patients never suffer from any symptoms [13, 22, 23], the absence of symptoms shortly before admission does not always imply that they are free from SARS-CoV-2 infection. Cheng et al. reported that all the second cases experienced their first exposure within 5 days of symptom onset in the index case . Next, we required patients to strictly avoid nonessential outings for 2 weeks prior to admission. RT-PCR testing, CT imaging, and a patient interview on lifestyle and symptoms are to be considered suitable approaches to identify ineligible patients, while staying at home is an appropriate method to a greater likelihood of safely “passing” the screening protocol. A “2-week stay” at home would allow asymptomatic patients to develop symptoms or remain asymptomatic or even cured with no, if any, transmissibility sequelae .
As a consequence, no surgeries were postponed due to suspected COVID-19 case, based on the RT-PCR, CT, and interview before admission approach, and no COVID-19-associated respiratory complications developed postoperatively or associated transmission was reported. In addition, we confirmed that there was no detection of the virus in samples obtained from tracheal tubes shortly after extubation in all patients. A sample from a tracheal tube reflects the lower airway as well as the upper airway because the tube comes in contact with the pharynx at removal. Therefore, tracheal samples are theoretically as reliable or more reliable than nasopharyngeal samples  and can be taken in a noninvasive manner. If the virus was detected, we could isolate and closely observe the patient on the day of surgery or on the next day, minimizing the risk of nosocomial infection or mortality after surgery.
Kobe has had no new COVID-19 patients in the middle of May, and the state of emergency was lifted on May 21 for Hyogo Prefecture. Considering the results of this study, our screening protocol can be simplified by omitting RT-PCR testing and CT imaging before hospital admission, depending on the institution and COVID-19 prevalence. COVID-19 vaccines have yielded promising results [27, 28]. If global herd immunity is successfully accomplished, preoperative screening might be unnecessary. However, when another COVID-19 wave may occur if a new virus variant is resistant to the vaccines or the efficacy does not last for a long term, avoidance of nonessential outings for 2 weeks prior to admission would be still an effective policy, which is thought to be the most powerful factor in our screening system.
The limitations of this study are as follows. The study was retrospectively conducted. Furthermore, the interviews relative to nonessential outings, contact with others, and patient symptoms were quite subjective and were based on self-assessment. The swab samples of tracheal tubes have never been tested, and we have never tested swab samples in active COVID-19 patients. Our successful resumption of elective surgeries may mainly be attributed to successful control of COVID-19 transmission at Kobe, Hyogo Prefecture.