Hospital transmission of COVID-19 in a general ward in Hong Kong

Hospital transmission of COVID-19 in a general ward in Hong Kong. Spencer EA, Heneghan C.

https://www.cebm.net/study/hospital-transmission-of-covid-19in-a-general-ward-in-hong-kong/

Published on June 30, 2020

Reference Wong SCY, Kwong RT, Wu TC, et al. Risk of nosocomial transmission of coronavirus disease 2019: an experience in a general ward setting in Hong Kong. J Hosp Infect. 2020;105(2):119-127.  2020
Study type
Country Hong Kong, China
Setting Hospital
Funding Details This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.
Transmission mode Aerosol, Droplet, Close contact
Exposures Close contact

Bottom Line

None of 120 contacts of a patient with initially undetected COVID-19 subsequently became infectious, suggesting SARS-CoV-2 is not spread by an airborne route. 

Evidence Summary

A total of 71 staff and 49 patients were identified from contact tracing, seven

staff and 10 patients fulfilled the criteria of ‘close contact’.  At the end of 28-day surveillance, 76 tests were performed on 52 contacts and all were negative, including all patient close contacts and six of the seven staff close contacts.  The remaining contacts were asymptomatic throughout the surveillance period

What did they do?

The study described an outbreak investigation of a patient with COVID-19 who was nursed in an open cubicle of a general ward before the diagnosis was made.  

An epidemiological investigation was instigated on 3rd February 2020, when a patient was diagnosed with COVID-19. The patient had stayed in an open cubicle a ward with 10

other patients for 35 hours (including 18.5 h of oxygen therapy) before transferring to an airborne infection isolation room (AIIR) (12 air changes per hour) for intubation with implementation of contact and airborne precautions.

Contacts were identified and risk categorized as ‘close’ or ‘casual’ for decisionson quarantine and/or medical surveillance. 

Close was defined as: ‘Staff close contact’ was defined as staff who had contact within 2 m of the index case for a cumulative time of >15 min, or had performed AGPs, without ‘appropriate’ PPE. ‘Appropriate’ PPE in the above contact episodes referred to the use of N95 respirator,

face shield/goggles, gown and gloves. Patients who shared the same cubicle with the index case were considered as ‘patient close contact’.

Staff close contacts were subjected to a 14-day work exclusion and quarantined at a designated campsite, followed by medical surveillance for another 14 days.  Patient close contacts were quarantined into an AIIR (or quarantine camp if the patient was deemed clinically stable to be discharged from hospital) for 14 days, followed by medical surveillance for 14 days. 

Other staff and patient contacts (‘casual contacts’) were subjected to medical surveillance for 28 days with no restriction to work or discharge from hospital. Body temperature and respiratory symptoms were monitored daily throughout the 28-day period. Any abnormalities were reported to the medical personnel at the quarantine camp, or to the hospital infection control team, with hospitalization into an AIIR and testing of SARS-CoV-2 where indicated.

Respiratory specimens were collected from contacts who developed fever, and/or respiratory symptoms during the surveillance period and were tested for SARS-CoV-2.

Study reliability

Study procedures for this case’s contacts were comprehensive.  The possibility of asymptomatic infection among the staff close contacts can not be entirely excluded as testing was not universal (only those with fever or respiratory symptoms).

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes No Yes Yes Unclear

What else should I consider?

The patient coughed frequently and  had a high viral load and she could not put on a surgical mask during her stay in the general medical ward.  All factors that would contribute to substantial droplet generation from the index patient. Despite this no neighbouring patients or staff contacts were infected. 

This study (of one case) implies that nosocomial transmissions can be prevented through basic barrier infection control measures, including wearing of surgical masks, hand and environmental hygiene.

About the authors

Carl Heneghan

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Elizabeth Spencer

Elizabeth Spencer

Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.