Open windows can reduce TB risk

A Toyota Quantum Ses’fikile model was used in a study to increase the risk for passengers to contract airborne diseases. Photo: Teboho Setena
A Toyota Quantum Ses’fikile model was used in a study to increase the risk for passengers to contract airborne diseases. Photo: Teboho Setena

Minibus taxis with closed windows increase the risk for passengers of contracting airborne diseases like tuberculosis (TB).

Researchers of the University of Cape Town (UCT) have figured out which windows one need to open to reduce the risk of TB infection.

Munyaradzi Matose and colleagues of the Division of Biomedical Engineering at UCT, fitted a 16-seater Toyota Quantum Ses’fikile model with a carbon dioxide sensor and assessed ventilation rates achieved by opening windows in different configurations in the taxi moving at 40 km/h, 80 km/h and 100 km/h.

While ventilation rates depended on both taxi speed and window configuration, they found that fully opening the two front windows in combination with either the two middle or the two back windows provided ventilation rates sufficient to reduce the risk of TB transmission.

“Seating positions receive different airflow according to occupancy and the window configuration used. The safest positions are those next to or directly behind an open window,” Matose said.

He said passengers expressed discomfort due to the speed of airflow directly reaching them and the temperature drop due to the airflow when the taxi was moving at 100km/h. This may force passengers to adjust windows to sub-optimal configurations, thereby redu­cing airflow and increasing the risk of transmission particularly for passengers in seating positions receiving less air.

“The risk of TB transmission in taxis is largely due to undiagnosed, untreated individuals who use public transport,” he said.

As minibus taxis are the most popular mode of transport in South Africa, Matose highlighted the importance of creating awareness amongst drivers and passengers over the risks of TB transmission in highly occupied taxis and the importance of maintaining good ventilation.

“The campaigns on opening windows cannot be once-off projects. The risks of airborne TB need to be given a greater drive given the extent of the TB epidemic,” he said.

As passenger discomfort and taxi occupancy may affect ventilation, he said other infection control measures, such as ultraviolet germicidal irradiation devices, filtration devices or mechanical ventilation to address the sub-optimal ventilation scenarios, must be considered.

“The ideal situation would be to have all new taxis equipped with the devices. For those already in operation, the cost can be carried by the vehicle owner with government subsidies. It is, after all, in the best interest of the driver and the passengers,” he concluded.

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