What is the chance of a new coronavirus contracting in a hospital? What is the level of air pollution? On March 4th, the journal of the American Medical Association (JAMA), the world’s top medical journal, published a Singapore team study of how the new coronavirus pollutes the air, the ground environment and personal protective equipment.
The study found that samples taken from uncleanward toilets, sinks, vents, etc. were positive for the new coronavirus, which meant that great emphasis must be placed on personal protection, ward cleaning and hand hygiene.
The study was conducted by the National Centre for Infectious Diseases of Singapore in conjunction with the National Laboratory of the National Institute of Defence Science and Technology of Singapore and was presented by Dr Kalisvar Marimuthu, Senior Consultant and Infectious Disease Specialist at the National Centre for Infectious Diseases of Singapore, and Dr Ng Oon Tek, who has worked on AIDS testing and drug development.
Unlike the usual research papers, letter-type papers are generally shorter in length and more time-sensitive, mainly because of the preliminary findings of some researchers’ new findings.
The authors note that many coronaviruses can lead to outbreaks in hospitals during transmission because of the environment being contaminated with the virus. There have been reports that the new coronavirus, which is currently spreading globally, has a pathway to spread in hospitals. However, the specific transmission of the new coronavirus and the extent of environmental pollution is not clear.
Earlier, on February 27, professor Hua Shucheng of Jilin University’s First Hospital published research results on the medical preprinting website medRxiv, confirming that in 28 air samples, air samples in the intensive care unit were tested positive for the new coronavirus.
This means that new coronaviruses may be present in hospital environments, whether in contact with air or surfaces, which can be contaminated and potentially at risk of infection.
In the Singapore team’s study, although the air samples collected were still negative, swabs taken from the exhaust vents of the isolation ward tested positive, suggesting that the virus could still move with small droplets such as aerosols in the air, so it was necessary to strictly strengthen the prevention of air infection in the isolation ward.
From January 24 to February 4, 2020, the researchers conducted sterile samples in the air-resistant isolation chamber (12 air exchanges per hour) of three patients at the New Coronavirus Special Medical Center in Singapore.
The isolation room had a front room and bathroom, and the researchers collected ground-based environmental samples from 26 locations, as well as samples of the doctor’s personal protective equipment (PPE) who left the ward.
All samples were collected over a five-day period of 2 weeks, with one sample taken in one patient room prior to routine cleaning and the other two patientrooms taking samples after routine cleaning. The 5000 ppm sodium dichloroisteanate is used twice a day in the ward to clean the patient’s frequent contact area, and the floor is cleaned with 1000 ppm of sodium dichloroisteanate perwhere.
The researchers took two days to take air samples, using a U.S. SKC universal pump (37 mm filter box and 0.3 micron Teflon filter) for indoor air samples, and for outdoor samples using Sedolis Sartorius, Germany. MD8 microbial samplers (with gelatin filters) are collected.
Subsequently, for RNA-dependent RNA polymerases and E genes, the team performed specific real-time reverse transcriptase-polymerase chain reactions (RT-PCR) to detect the presence of new coronaviruses.
They use the cycle threshold (Cycle threshold value, Ct value) to quantify the virus load in the sample, the Ct value is the number of cycles required for the fluorescent signal to reach the threshold in the RT-PCR, the lower the Ct value, indicating that the virus load is higher.
The researchers also collected clinical data (symptoms, date of onset, and RT-PCR results) and cleaning time, and associated them with sample results, while the team tested positive if the room environment swab was positive for the new coronavirus.
For patient A, the researchers sampled the room on the 4th and 10th days of their illness, when A had symptoms and the samples were taken after routine cleaning in the ward, all of which were negative.
Patient B had symptoms on the 8th day of the disease and no symptoms on the 11th day, and the researchers took samples after routine cleaning in the ward, and the samples were negative.
Sample time, patient symptoms, etc. and clinical Ct values
Samples from patient Ward C were collected prior to routine cleaning on the same day and showed that 13 of the 15 rooms (including exhaust fans) were HIV-positive (87 per cent) and 3 (60 per cent) were positive in 5 toilets (toilets, sinks and door handles).
Partial sampling points (patient rooms and bathrooms) and RT-PCR results
Samples from the front hall and corridor of the ward where patient C is located were negative. Patient C has upper respiratory symptoms, but no pneumonia. Although there were no diarrhea symptoms, its RT-PCR results showed that two stool samples were virus-positive.
Of the samples of personal protective equipment collected, only one shoe swab was positive and all other personal protective device swabs were negative for the new coronavirus.
Notably, in this anti-air infection lab, all air samples taken by the researchers were virus-negative.
The researchers believe that a patient with a new coronavirus with mild upper respiratory symptoms could lead to a wider range of environmental pollution. Both toilet and sink samples are positive, suggesting that the spread of the virus in the faeces may be a potential route of transmission. Samples taken after routine cleaning are negative, indicating that the current cleaning measures are in place.
Studies have shown that air samples are negative despite environmental pollution. But the study also stressed that swabs collected from the vents tested positive, suggesting that small droplets containing the virus in the air may have been deposited on devices such as vents as airflow displaced. It is not surprising that positive samples taken on PPE are also at low risk of contaminated footwear spreading the virus, as samples taken in the front hall and clean corridors are negative.
The researchers also point out that the study has several limitations. First, they did not undergo virus culture to prove their viability for the sample results. Second, due to operational limitations during the outbreak, the sampling method is inconsistent and the sample size is very small. Third, the amount of air sampled is only a fraction of the total volume, and indoor air exchange dilutes the presence of airborne viruses. They therefore believe that further research is needed to confirm these preliminary results.
The authors conclude that patients with the new coronavirus cause serious environmental pollution through respiratory droplets and feces, suggesting that the environment in which the patient is located is a potential vector and requirestrict environmental hygiene and hand hygiene.