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Risk of infection from surfaces is low, study finds

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The risk of catching Covid-19 by using a push button at a pedestrian crossing or a pay terminal keypad is low, according to two studies by Eawag, the Swiss Federal Institute for Aquatic Science and Technology.

Back in May last year, Flemish mobility minister Lydia Peeters issued advice for people to push the button at pedestrian crossings using their elbow, to avoid the risk of contamination by touch. In October, the city of Antwerp began adapting the push-buttons at crossings to make elbow operation easier.

According to the new research, those precautions were most likely unnecessary.

The first study took 350 samples between April and June 2020 from entrance door handles at businesses, door handles, dustbin handles, ATM keypads, petrol pumps and traffic-light buttons. About 8%, or 29 samples, showed genetic material from the coronavirus. However concentrations were too low to conclude there was a risk of infection – a less than five in 10,000 chance, the study estimated.

Another study, carried out at Imperial College London, estimated the comparative value of hand and surface disinfection, and discovered that surface disinfection depends on a variety of factors and is of limited value, hand disinfection on the other hand reduces the chance of infection substantially.

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One situation that was not studied, however, was the possible danger of objects that may be exposed to prolonged exposure to the virus, such as dishes and surfaces in a restaurant, explained Timothy Julian of Eawag’s environmental microbiology department.

The likelihood that someone will cough or sneeze over a table, and that droplets with high viral loads will be found there, is much greater than in the case of a button or a door handle – so it remains very important that tables are disinfected and dishes properly washed,” he said.

The organisation also stresses that, although the danger to individuals of infections from high-touch surfaces may be low, the regular collection of samples from such surfaces could be useful in tracking the progress of the disease.

As with wastewater sampling, surveillance of SARS-CoV-2 RNA on high-touch surfaces could be a useful tool – in addition to clinical tests – for providing early warning of COVID-19 case trends.”

Alan Hope
The Brussels Times