The Irish Times view on Covid-19 transmission: policy must move with the evidence

Covid-19 is spread through exposure to very small respiratory liquid particles released in the exhaled breath of an infectious individual. That was not always understood. In the early stages of the pandemic, medics emphasised the importance of large respiratory droplets such as those sprayed from coughs or sneezes. But numerous studies have made it increasingly clear that the virus is airborne: it is enough for someone merely to breathe, talk, sing, shout or laugh and by so doing to spread Covid-19. The risk increases if people are in close proximity or spend a prolonged period in the same space, but these particles can also travel over longer distances, especially in crowded environments where ventilation is poor.

These insights do not invalidate the general public health advice that Government ministers and officials have repeated so often since March 2020. Social distancing, vaccination, good cough and respiratory etiquette, meticulous hand hygiene and wearing a face mask can all reduce transmission. They remain essential tools against Covid-19. But if, as now seems clear, Covid is an airborne virus – and by extension a virus that people for the most part acquire indoors – then the focus must be on keeping that air clean.

The importance of good ventilation is now incorporated into regular public health guidance, and the introduction of CO2 monitors in schools was belated acknowledgment of its importance. It is also welcome that the Government is making €72 million available to schools and childcare facilities to improve their ventilation. Yet there remains a sense that clean air remains an afterthought. It should instead be at the heart of the State's mitigation measures as well as its public communications. With the Omicron virus likely to sweep across Ireland in the coming weeks, the need to take airborne transmission seriously is even more urgent.

Air filtration systems should be required in high-risk buildings. Businesses should be warned about the dangers of air-conditioning units that simply re-circulate air. Bars and restaurants can be sanctioned for not checking the Covid vaccination pass, but it should be just as socially unacceptable to serve customers amid filthy, untreated air. Members of the public can also play their part by shunning buildings that are overcrowded or lack adequate ventilation. It does not matter how much distance there is between tables if they are surrounded by infected air.

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Orla Hegarty, assistant professor of architecture in UCD, has suggested that half of all the people who have died from Covid-19 in Ireland were infected in fewer than 400 buildings. Such patterns cannot be ignored. Now that we know how people get infected – and how that transmission can be broken – the case for a shift in priorities ought to be as clear as the air we breathe.