Covid-19 'exceptionally contagious in crowded offices', study finds

A new study has highlighted the importance of busy workplaces as an incubator of the coronavirus as the World Health Organization has said that there is “emerging evidence” that Covid-19 can be spread through the air.

The study, published in the journal Emerging Infectious Diseases, looked at the spread of coronavirus in a call centre in South Korea in March, where 43.5 per cent of people working on one floor of the building tested positive for the disease.

After an employee fell ill with the virus health officials tested 1,143 of his or her colleagues and found that 97 tested positive - 94 of whom worked on the same floor of the office. The majority all worked on the same side of the building, many sitting next to or opposite each other.

The authors wrote that the outbreak showed that Covid-19 “can be exceptionally contagious in crowded office settings such as a call centre”.

“The magnitude of the outbreak illustrates how a high-density work environment can become a high-risk site for the spread of Covid-19 and potentially a source of further transmission,” they added.

An earlier study in the same journal looked at an outbreak among 10 diners at a restaurant in Guangzhou, China in January. The diners were sitting at three separate tables and researchers believe that airflow from an air conditioning unit could have spread droplets between the three groups.

The question over how the disease is transmitted has been given added urgency in recent days after a group of more than 200 scientists wrote an open letter to the WHO urging officials to recognise the possibility of airborne transmission of the virus.

Current guidelines from the WHO focus on the virus being spread primarily through droplets from the nose or mouth, which are expelled when an infected person coughs, sneezes or speaks. WHO currently recommends that the best way to avoid picking up the virus is through hand washing and social distancing.

But signatories of the letter, published in the Clinical Infectious Diseases journal, have called on health officials to update guidance to include measures to prevent airborne transmission, such as providing sufficient ventilation, minimising recirculating air, and avoiding overcrowding - particularly on public transport.

Speaking at an event at Chatham House on Wednesday Professor David Heymann, infectious diseases expert and an adviser to WHO, said there was a possibility that there could be “airborne transmission of the virus in enclosed spaces”.

“There are some studies that are going on now. And WHO is waiting to see these results. One of these is to put an animal that can be infected with this virus into various places around rooms, in hospitals or wherever to see if those animals are being infected. And that's being done with hamsters,” he said.

True airborne spread of the virus would mean it could carry much further than the one to two metres scientists currently say it would spread. It would mean that people could be at risk outside, whereas most experts believe outdoor transmission of Covid-19 is very unlikely.

Prof Heymann said Switzerland,which has a low reproduction number and where people are beginning to congregate, showed that airborne transmission was unlikely.  “There's not been any indication that this is just airborne and spreading in the community. .. If this is airborne, it can impact people walking down the street,” he said.

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