Researchers at Toyonaka Municipal Hospital in Japan have shown that the rate of subclinical infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among staff at the hospital is no higher than among the general population in the same area.
Tsutomu Nishida and colleagues say the findings demonstrate the effectiveness of the nosocomial infection control measures that were introduced, as recommended by the Japanese Society for Infection Prevention and Control and the National Center for Global Health and Medicine.
“The results of this study demonstrated that our nosocomial infection control measures have thus far been successful,” writes the team.
A pre-print version of the paper is available on the server medRxiv*, while the article undergoes peer review.
Hospital staff are at the frontline of efforts to control the pandemic
Since the first cases of COVID-19 were identified in Wuhan, China, late last year, the causative agent SARS-CoV-2 has spread to almost every country in the world and infected more than 29 million people.
Hospital staff are at the front line of efforts to control the ongoing pandemic and are at an increased risk of transmitting the highly infectious virus. Nosocomial infection among hospital staff can therefore be problematic, and one study reported that the virus is often detected among hospital staff, even when they are not involved in the care of COVID-19 patients.
The authors of the current study say that although Japan has been more successful at controlling disease spread than some other countries and has maintained a comparatively low incidence of infections in hospitals, the subclinical rate of infection among staff during the pandemic remains unclear.
About Toyonaka Municipal Hospital
Toyonaka Municipal Hospital, which is located in an urban area of the Osaka Prefecture, provides 613 beds, including 14 in the Infectious Disease Unit, and is a designated institution for type II infectious diseases.
“Our hospital is located in the pandemic region in Japan,” writes the team. “At the government's request, we were the hospital to accept four asymptomatic COVID-19 patients from the cruise ship, the Diamond Princess, on February 22, 2020. After that, COVID-19 spread in Japan, and the number of patients admitted to our hospital gradually increased.”
Between February 22 and May 31, the hospital accepted 75 COVID-19 patients and performed 415 nasopharyngeal swabs to test for SARS-CoV-2 infection, 61 (14.7%) of which were positive.
Basic infection control measures have been introduced at the hospital in accordance with manuals produced by the Japanese Society for Infection Prevention and Control and the National Center for Global Health and Medicine.
Staff have used personal protective equipment when caring for people with confirmed or suspected COVID-19, including N95 masks, face shields, gowns, double gloves, and caps.
“Under the current circumstances, it is important to investigate the subclinical SARS-CoV-2 infection rate in our staff and to evaluate the effectiveness of our nosocomial infection control measures,” say Nishida and colleagues.
What did the investigation involve?
Now, the team has tested for the prevalence of subclinical infection among 925 hospital staff (aged a mean of 40 years) using a test for the anti-SARS-CoV-2 antibody immunoglobulin g (IgG).
The test, which is called the Abbott immunoassay, has a sensitivity of 100% and a specificity of 99.6%.
The researchers also explored risk factors associated with seropositivity using a survey composed of questions about background, general health, involvement with general patients, and involvement with patients with suspected or confirmed COVID-19.
Among the staff, 149 (16%) were doctors or dentists, 489 (52.9%) were nurses, 140 (14.2%) were technologists, 49 (5.3%) were healthcare providers, and 98 (10.5%) was the administrative staff.
What did they find?
Four of the 925 staff were seropositive for anti-SARS-CoV-2 IgG, representing a subclinical infection rate of 0.43%.
“Considering that the sensitivity of this assay is 100%, the true-positive rate in our hospital should be less than 0.43%,” writes the team.
The researchers say this seroprevalence of 0.43% is similar to or less than the seroprevalence of 0.54% (16/2970) that was identified using the same assay in a government survey of the general population in Osaka over the same period.
The prevalence of seropositivity did not significantly differ by job role, exposure to suspected or confirmed COVID-19 cases, or any other factors investigated.
“We have thus far successfully managed to avoid hospital-acquired infections”
“The results of this study demonstrated that our nosocomial infection control measures have thus far been successful,” say Nishida and colleagues. “Compared with the seropositive rate of 0.54% in the general population in Osaka, our results indicate that we have thus far successfully managed to avoid hospital-acquired infections.”
However, the study shows that timely serological screening of a large cohort is essential for achieving control during the pandemic, say the researchers.
“Hospital-based antibody screening could also help us evaluate and monitor infection control,” they conclude.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
- Nishida T, et al. Seroprevalence of SARS-CoV-2 Antibodies Among 925 Staff Members in an Urban Hospital Accepting COVID-19 Patients in Osaka Prefecture, Japan. medRxiv, 2020. doi: https://doi.org/10.1101/2020.09.10.20191866