According to recent study, hospitalized patients are at potentially high risk of getting Covid-19 if their roommate tested positive for SARS-CoV-2 suggesting a high probability of transmission for patients in shared hospital rooms.

The retrospective study published in the journal Clinical Infectious Diseases attempted to characterize the incidence and risk factors for transmission of SARS-CoV-2 among patients in shared hospital rooms at Brigham and Womens Hospital in Boston between September 2020 and April 2021.Several protocols to prevent nosocomial spread of SARS-CoV-2 were in place in the hospital.

The number of adult patients hospitalized during the study period was 25,751. Of these, 599 tested positive for Covid-19 at the time of admission. 11,290 patients were admitted to shared rooms; 25 of these tested positive after admission, the “index cases”. The cycle threshold (Ct) values on RT PCR of index cases were ≤21. These patients had 38 roommates during the period they were potentially infectious; some of them had more than one roommate before they were diagnosed. Exposure was considered as sharing a room for ≥15 minutes with an index patient during their infectious window (48 hours prior to symptom onset or positive test in the absence of symptoms) until isolation.

Thirty-one out of the 38 exposed room mates were included in the analysis as they had ≥1 documented test ≥3 days after exposure to Covid-19. Of these, 12 tested positive within 14 days, which denotes a secondary attack rate of 39%. Only one index case and two roommates had been fully vaccinated at the time of exposure. One vaccinated roommate was infected by an unvaccinated index case.

Researchers also endeavored to identify the potential risk factors for transmission. Duration of exposure, viral load, symptomatic patient, aerosol-generated procedures (use of nebulisers, high flow nasal cannula or non-invasive positive pressure ventilation) were some of the factors assessed. Agitated or yelling patients were also considered among the risk factors evaluated. Viral load (as denoted by Ct value) was found to be only risk factor to have a significant association with transmission. Patients sharing rooms with individuals with very low Ct counts, which were ≤21, were at highest risk.

Contact with shared surfaces such as sinks, door handles, or bathrooms may be other possible routes. Regular cleaning and disinfection is crucial.

Ten patients in the study tested positive 4-5 days after their discharge from the hospital. This emphasizes the significance of active follow up of the discharged patients, who may have been potentially exposed to the infection during their hospital stay in shared rooms.

All hospitals have implemented preventive measures to check SARS Cov-2 infection ranging from universal masking of healthcare workers to routine screening of patients for possible COVID-19 symptoms, isolation of suspected cases, universal testing (RT PCR) on admission and 72 hours later and testing in case of any new symptoms suggestive of Covid-19. Nevertheless, there may be a rare case or two that may slip through the net. Although the absolute risk of acquiring infection in shared rooms was only 0.1%, the secondary attack rate was 39%. This study highlights the need for enhanced infection prevention measures to reduce transmission risk between roommates especially when the number of cases in the community is very high.

Some mitigation strategies as recommended by the researchers include “awaiting SARS-CoV-2 tests results before admitting to shared rooms, (a potential application of rapid testing platforms), requiring patients in shared rooms to wear masks (at least while admission tests are pending), routine serial testing of patients in shared rooms, only placing vaccinated patients in shared rooms, improving ventilation by increasing air changes per hour, and/or placing portable HEPA filters between roommates.”

(Source: Medpage Today, July 17, 2021; Clinical Infectious Diseases, June 18, 2021, https://doi.org/10.1093/cid/ciab564)

Dr Viny Kantroo, Consultant Respiratory, Critical Care & Sleep Medicine, Indraprastha Apollo Hospitals, New Delhi, India

Dr Sanjay Kalra, DM, Bharti Hospital, Karnal; Immediate Past President, Endocrine Society of India