Study looks at SARS-CoV-2 RNA contamination in COVID-19 isolation ward of a hospital
By Dr. Liji Thomas, MDNov 15 2020
The coronavirus disease 2019 (COVID-19) pandemic is progressing rapidly. With many parts of the world experiencing second waves of infections, over 54.32 million cases and 1.31 million deaths have been reported globally.
Despite extensively studying the disease and the novel coronavirus that causes it – severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – scientists have not been able to come up with a comprehensive description of how the virus spreads.
To try and shed more light on SARS-CoV-2’s transmission, a research group based in Italy examined a COVID-19 isolation ward in a Milan hospital to evaluate the level of contamination present in the air and on surfaces with SARS-CoV-2 RNA (the virus’s genetic material).
Study: Targeting Neutrophils to Treat Acute Respiratory Distress Syndrome in Coronavirus Disease. Image Credit: SweetHour / Shutterstock
The group published their findings in the journal Science of the Total Environment on November 10, 2020.
With relatively high mortality and an even larger proportion of serious morbidity, this virus has already bulldozed many countries in the European Union. Italy was the first, and among the worst, affected when the first wave of COVID-19 reached the region earlier this year (2020). Italian healthcare facilities were overwhelmed by seriously sick and dying patients. The most intense outbreak was in the Lombardy region in Northern Italy, which accounted for almost half of the approximately 35,00 deaths in the country.
Airborne and fomite spread
The virus spreads via respiratory droplets and aerosol, directly or when these secretions contaminate the hands or other objects or surfaces. The virus can survive in an infectious form on surfaces for days and in aerosols for hours. Hospitals are ideal settings for viral transmission, given the fact that infected people have high viral loads that are released into the surroundings by coughing and sneezing. In such closed surroundings, it has been shown that respiratory droplets may remain suspended in the air for at least 10 minutes.
Contamination of air and surface samples
The scientists obtained 5 air samples and 37 surface samples from five distinct areas of the isolation ward. The ward had a negative airflow air conditioning system. All areas received a daily cleaning with disinfectants containing 5-10% chlorine. The samples for this study were collected before the daily cleaning.
The samples were then classified into three groups: as contaminated (patients area in the intensive care unit or ICU, and the corridor), semi-contaminated (the area where staff undressed), and the clean areas (lockers, dressing room and passage for medical staff). These were separated by watertight automatically closing doors. At the time of the study, there were three COVID-19 patients in the ICU.
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The researchers used real-time reverse transcription-polymerase chain (RT PCR) to detect the viral RNA.
They found that about a quarter of swabs collected from the contaminated and semi-contaminated areas were PCR positive. When classified by area, half the swabs and a third of the swabs from the semi-contaminated and contaminated areas, respectively, were positive.
Overall, the areas of most significant contamination were found to be the hand sanitizer dispenser, a single swab from which showed contamination; medical equipment and touch screens used for such equipment, which was contaminated in half the cases; shelves housing medical equipment, at 40%, bedrails in a third of cases, and door handles in a quarter of samples.
However, taking only contaminated areas into consideration, two-thirds of medical equipment swab was positive, and half the bedrails. The presence of viral RNA in staff dressing rooms shows it is important to separate semi-contaminated and clean areas, and to provide separate dressing and undressing rooms.
Another finding was that no wall samples were positive. Thus, it is easy to infect frequently touched objects, perhaps by viral shedding. A positive PCR may not indicate viral shedding, and hence viral infectivity, but may indicate a lapse in cleanliness and disinfection. Moreover, the study should emphasize the need to clean every item, including medical equipment, to restrict viral spread. Hand hygiene may also be essential to break the chain of transmission.
Air samples from the contaminated area were universally positive. None of the other air samples were positive. Notably, in this study, all the clean areas of the ward were negative for the virus. These findings agree with earlier studies that suggest airborne spread is dominant for SARS-CoV-2.
Reassuringly, none of the swabs from the clean area, or air samples, were positive for the virus.
The study concludes: “Environmental contamination did not involve clean areas, but the results also support the need for strict disinfection, hand hygiene and protective measures for healthcare workers as well as the need for airborne isolation precautions.”
Such precautions may include ensuring an adequate ventilation rate of 288 m3 per hour, indoor air purifiers competent for the space covered, as well as the training of staff with regard to face mask/shield/respirator use and handwashing. This is in addition to continuing intensive cleaning and disinfection routines.
The authors point out, “Medical and, in particular, electronic equipment needs particular attention as it is possible that their cleaning is intentionally neglected to avoid interference with medical procedures.” This loophole needs to be addressed.
Home isolation is unlikely to be effective in this context. It typically lacks the protective measures or training required to limit the spread of infection but might be opted for as a last resort if hospitals cannot cope with the flow of critically ill patients.
Thus, the study demonstrates the need for strict protective measures, both built-in and personal, to prevent the spread of infection from patients to staff within healthcare facilities. It also highlights the efficacy of physical barriers and proper protective behavior to prevent airborne spread. Further studies will help establish the boundaries of protective behavior required to contain this threat within such settings.