Researchers report that no hospital acquired infections occurred among healthcare workers at public hospitals in Hong Kong after the first 6 weeks of the SARS-CoV-2 outbreak — even though these hospitals dealt with 42 confirmed cases of COVID-19.
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Dr. Vincent C.C. Cheng, from the Department of Microbiology at Queen Mary Hospital, in Hong Kong, is the lead author of the new study.
Dr. Cheng and the team inventoried the infection control measures implemented by the Hong Kong Hospital Authority, “a governing body of all 43 public hospitals, responsible for 90% of inpatient service in Hong Kong” immediately after the COVID-19 outbreak in Wuhan, mainland China.
The findings indicate that standard infection control practices are effective if conscientiously applied.
The scientists also examined the epidemiology of the confirmed cases that these hospitals dealt with, as well as collecting and analyzing environmental and air samples to see how much the virus had spread in the environment.
The researchers published their findings in Infection Control & Hospital Epidemiology, the journal of The Society for Healthcare Epidemiology of America.
Dr. Cheng and colleagues started their calculations with “day 1” — December 31, 2019, the day when a cluster of pneumonia cases was announced in Wuhan, China.
The aim of the study was to evaluate the preparedness for COVID-19 in the following 42 days, or 6 weeks.
During this time, the 43 hospitals included in the analysis tested 1,275 suspected cases of COVID-19 and treated 42 confirmed cases — that is, 3.3% of the suspected cases.
A total of 413 healthcare workers treated the confirmed cases. Eleven of these employees had unprotected exposure to SARS-CoV-2 and were therefore quarantined for 14 days.
None of the quarantined staff members contracted the virus, report the researchers. Furthermore, no hospital acquired infections occurred after 6 weeks.
To further investigate the environmental transmission of the virus, Dr. Cheng and the team took eight air samples at a distance of 10 centimeters (cm) from the chin of a patient with COVID-19.
The patient had a moderate viral load. The scientists collected the samples while the patient followed instructions to, alternately, breathe normally, breathe heavily, speak, and cough, with and without a surgical mask.
The researchers also performed an environmental analysis of one patient with a moderate viral load — that is, they tested 13 surfaces around the patient.
None of the eight air samples tested positive for SARS-CoV-2. Only one of the 13 environmental samples tested positive for the virus, representing 7.7% of the surfaces analyzed.
Dr. Gonzalo Bearman, a professor of medicine and Chair of the Division of Infectious Diseases at Virginia Commonwealth University, in Richmond, reviewed the study but was not involved in the research.
“The descriptive study employed unique environmental and air samples, with the results suggesting that environmental transmission may play less of a role than person-to-person transmission in disease propagation.”
– Dr. Gonzalo Bearman
The hospitals in Hong Kong implemented infection control measures that included widening screening criteria to include visits to hospitals in mainland China and immediately isolating people with SARS-CoV-2 in airborne infection isolation rooms.
Sometimes, the patients were isolated in a ward where they were positioned 1 meter apart from each other.
In the first 42 days of the outbreak, the number of COVID-19 cases in which SARS-CoV-2 had been contracted locally, in Hong Kong, increased significantly.
Specifically, the number of locally contracted infections jumped from 1 of 13 confirmed cases (or 7.7%) at day 32 to 27 of 29 confirmed cases (or 93.1%) between day 33 and day 42.
Among these cases, 28 were tied to 8 family clusters, and 11 were tied to a single family cluster.
These 11 cases were “most probably transmitted during [the family’s] gathering for hot pot, where [the] use of utensils and chopsticks contaminated by saliva may occur,” note the authors.
As for transmission within hospitals and the protection of healthcare workers, standard practices of infection control are effective, concludes the study.
“Appropriate hospital infection control measures can prevent healthcare-associated transmission of the coronavirus,” write Dr. Cheng and colleagues. They conclude:
“Vigilance in hand hygiene practice, wearing of surgical masks in the hospital, and appropriate use of personal protective equipment in patient care, especially when performing aerosol-generating procedures, are the key infection control measures to prevent hospital transmission of the virus.”
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