Good ventilation is a key factor in reducing new Covid-19 infections

The looting and unrest in KwaZulu-Natal and Gauteng in mid-July 2021 was, from a Covid-19 perspective, a damp squib. There is no clear evidence in the numbers to support the dire predictions at the time that the gatherings of thousands of people to loot and burn property would be a super-spreader event.

True, the Institute for Water and Wastewater Technology found an increase in infected effluent at the eThekwini Central Wastewater Treatment plant two weeks later. But other simultaneous factors make it difficult to draw simplistic conclusions: the whole country had just moved from level 4 to level 3 lockdown and infection rates were still rising everywhere. In fact, the graphs show that the trajectory in infections in KwaZulu-Natal during that period mirrors that of the Western Cape, where there was no looting.

To analyse this in depth would take considerably more than a quick glance at the graphs. It is very likely that there was at least some increase in transmission from crowd behaviour. However, we believe there was a fundamental, often-overlooked reason why this was not a super-spreader catastrophe.

Unlike the disastrous Matric Rage events in late 2020, the unrest in KwaZulu-Natal and Gauteng for the most part, took place in the open air, not within confined or poorly ventilated spaces. It underlines the importance of good ventilation – a critical public health factor that has not been prioritised or emphasised enough in all the public health messaging advice dispensed by the government and other leading institutions – to effectively limit Covid-19 transmission.

Scientists and specialists of the GreenFlag Association have been closely following the science both retrospective and emerging from around the world since the beginning of the pandemic. Looking at the quality and strength of the overall evidence base, there is consistent strong evidence that SARS-CoV-2, and particularly the Delta variant, spreads by airborne transmission and that aerosols are one of the most important ways this virus is transmitted. These aerosols are small enough to remain suspended or float in the air for minutes or even hours, and can travel much further than 10 metres, depending upon the airflow.

It is at this stage also important to note the underestimated and widely misunderstood role ventilation has in reducing the transmission of this and many other airborne diseases. Ventilation means fresh air coming into an indoor space from outside, for example through open doors, windows, simple extraction and supply fans, as well as HVAC or central air conditioning systems which should draw in just enough outdoor air to prevent a build-up of exhaled air and other bio effluents.

This should not be confused with commonly used split-unit air conditioners, designed for energy efficiency for cooling. Split units simply keep cooling and recirculating the air existing within the room, allowing for a build-up of exhaled air, aerosols and other pollutants released in the room. In this case the air may feel cool and fresh, however it can be anything but fresh.

Governments’ legal guidelines about ventilation, both locally and internationally, are relatively vague since the provision of fresh outdoor air can be somewhat complicated based on variables such as the number of occupants within the indoor space and the volume of the space and access to natural airflow.

In its Consolidated Directions, the Department of Employment and Labour advises employers to have ventilation systems that function effectively and not simply recirculate used air. The intention is to prevent an accumulation of exhaled air and other bio-effluents within poorly ventilated workplaces. These are the spaces in which airborne pathogen transmission occurs. They are the persistent reservoirs of superspreader events.

As businesses, schools and universities consider bringing staff and students back into offices and classrooms, it raises the risk of more extreme waves of Covid infections. The problem is, we are stuck in the thinking of almost two years ago. Our Covid public health messaging has not been adequately updated in response to our better understanding of how infectious and contagious the Delta variant actually is.

Many still believe that surface sanitation, air fumigation, physical barriers, hand sanitation and social distancing will effectively help prevent the spread of Covid-19 and other airborne pathogens. This is simply misleading, resulting in unnecessary adverse health consequences as well as excessive, misplaced and ill-afforded expenditure.

The truth is vaccination and appropriate indoor ventilation are the two most significant factors for reducing the risk of deaths and transmission respectively. Masking and hand sanitation are important public health prevention measures, but there needs to be some hierarchy of these controls if we want to save lives effectively and efficiently, with limited expenditure and resources.

To protect employees and customers from Covid-19, business owners need to understand that it is the provision of sufficient ventilation that is as important – if not more important – than masking when it comes to preventing the spread of Covid-19.

Both the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) have emphasised that Covid-19 is airborne and can be transmitted at distances much greater than one metre. The CDC, in particular, warns about the risks of enclosed spaces with inadequate ventilation, increased aerosol emissions through exhalation from physical exertion, raised voices, and prolonged exposure in these conditions for more than 15 minutes.

If we consider South Africa’s current decline in vaccination rates, the importance of ventilation and general lack of adherence to masking and physical distancing protocols, then the worst place to be is probably in a taxi or other public transport such as ride hailing services, buses and trains, with the windows shut. Poorly ventilated spaces with high occupation densities, like factories, board rooms, offices, classrooms, indoor restaurants, churches and of course, indoor venues like matric rages, are all potential ongoing superspreader reservoirs.

In the open air, unless you are walking or running directly behind an infected person and breathing in their exhalation plume, you are at a far lower risk of Covid-19 infection.

Covid-19 is likely to be with us for a long time, like HIV, influenza, chicken pox, measles and TB. To tackle it effectively, we will have to live with, and manage, it. Business owners and institutions have an obligation to make sure their premises are safe for returning workers, customers and students. One of the most effective things that businesses, schools and universities could do to ensure their staff, customers and students are safe, is to ensure all their public indoor spaces are effectively ventilated with fresh outdoor air. DM