With scientists predicting that a fourth wave of Covid-19 infections will hit South Africa towards the end of this year, GreenFlag Association exposure scientists and medical specialists say that the number of infections can be limited by combining an intensified vaccination roll-out programme with a diligent focus on clean air and ventilation of indoor spaces.

GreenFlag, which has been following the science related to the pandemic, said during a November 16 webinar that “proper ventilation of indoor spaces is the missing ingredient and that we will see another wave if we continue to ignore it”.

“There is a large amount of convincing evidence that SARS-CoV-2, like other respiratory viruses, spreads through the air,” said Western Reserve University assistant professor Dr Gareth Kantor, adding that very few cases have been reported that resulted from touching contaminated surfaces.

He said the majority of transmissions have been from people without obvious symptoms of the Covid-19 virus.

“We know Covid is seldom acquired outdoors. The virus spreads in rebreathed air that accumulates in crowded, poorly ventilated indoor spaces. This includes public transport – taxis, buses  – and private vehicles. In many cases, multiple people are infected at one time,” he said.

Scientific data show that 20% of infectious persons lead to about 80% of the total cases.

Kantor and Apex Environment technical director Sean Chester discussed the underestimated and unappreciated role of ventilation in reducing the transmission of Covid-19 and other airborne diseases, like tuberculosis.

Chester is also a panel member of the GreenFlag Association.

They explained that 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 heating, ventilation, air-conditioning and cooling (HVAC) or central air conditioning systems.

Air conditioning systems should draw in enough outdoor air to prevent a build-up of exhaled air and other bio-effluents.

They warned that this should not be confused with commonly-used split unit air conditioners which simply keep cooling and recirculating the air in a room, allowing for a build-up of exhaled air, aerosols and other pollutants released within the room.

In this case, the air may feel cool and fresh, but it “can be anything but fresh”.

“When you enter an occupied space, you are in fact potentially entering a high transmission risk environment where the air you breathe is largely the exhaled air from the other occupants,” said Chester.

He warned that people in indoor spaces are 20 times more likely to become infected with Covid-19 than those in outdoor spaces, emphasising that improving ventilation of closed occupied spaces significantly lowers the risk of catching the virus.

Crowded indoor public spaces, such as offices, schools, churches and public transport are some of the major hotspots when it comes to spreading the disease, as Covid spreads through tiny aerosols that can hang suspended in the air for long periods of time.

The concentration of viral particles rapidly increases, making unventilated spaces potential super-spreader areas, and “simply opening enough windows can prevent this”.

“In South Africa, taxis, which transport about 12-million people a day, are vital to everyday life but [are] areas of great danger,” said Kantor, adding that “taxis are confined environments where up to 16 people sit closely together. If windows are not opened, a simple trip to work or to the shops can become a super-spreader event.”

Taverns and bars are another area of concern when filled with unmasked people speaking loudly, singing or shouting – activities that cause a ten-fold increase in the emission of infectious aerosols.

“A ‘loud crowd’ indoors is a super-spreader event waiting to happen,” Kantor commented.

The World Health Organisation has acknowledged that Covid-19 is an airborne disease but South Africa’s Covid-19 public health messaging has not been adequately updated to reflect this, states GreenFlag.

“Many people still believe that surface and hand sanitation guarantee the prevention of Covid, even though it is an airborne disease,” said Chester.

“Social distancing and wearing a mask are still important because the tiny floating aerosols which contain the coronavirus can be transmitted both up close and at a distance. But without ventilation, the distancing is much less effective.

“At the same time, there is ongoing, misplaced expenditure on temperature scanning, fumigating and physical barriers which can actually trap the vital flow of air.”

The association, therefore, called on government, media, business and other organisations such as the Solidarity Fund and Business4SA, to support practical ventilation interventions and ensure South Africa’s Covid protocols and messaging are updated and properly communicated.

“Vaccination and appropriate indoor ventilation are the two most significant factors for reducing the risk of Covid-19 transmission and death. If we want to save lives and mitigate or prevent the predicted fourth wave, we should emphasise both these critical measures in the fight against Covid,” said Kantor.

“Now is the time to take action. Only when cases are low, vaccination rates high, and we have decently ventilated public spaces will we be able to resume a more normal life, and remove our masks.”