Curbing the spread of airborne diseases

Deidre Lotter 

The CSIR is investigating the role of architectural engineering processes in improving the design of healthcare facilities, particularly to prevent the spread of airborne diseases such as TB.

South Africa faces one of the most devastating tuberculosis (TB) epidemics in the world, with the World Health Organization ranking the country second in terms of TB incidence (or the number of cases per capita) and ninth in terms of the actual number of TB cases. In response to this challenge, the CSIR is investigating the role of architectural engineering processes in improving the design of healthcare facilities, particularly to prevent the spread of airborne diseases such as TB. The CSIR’s research, led by Dr Sidney Parsons, seeks evidence-based interventions to minimise risk within healthcare facilities. Parsons believes that architectural engineering processes can play a crucial role in designing healthcare facilities that are fit-for-purpose, especially in areas related to infection control. “Combining microbiology with architectural engineering can result in a better understanding of the spread of airborne diseases,” he explains. 

TB is an infectious disease transmitted from person to person by the airborne route, usually through coughing by a patient with active pulmonary TB. “Infectious droplet nuclei containing tubercle bacilli may remain suspended in the air for prolonged periods of time, leading to a high risk of infection in hospitals, clinics and other congregate settings with poor or little ventilation where susceptible populations – such as children and immune-suppressed individuals – may be accommodated,” says Parsons. 

A serious complication of the TB problem in South Africa has been the emergence of multi-drug resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) in all nine provinces.

Multidrug resistance (MDR) emerges when there is defaulting in treatment or mismanagement of drugs. MDR-TB does not respond to standard treatments and is defined as being resistant to the main first-line drugs, isoniazid and rifampicin. It can be spread from one person to another. The cost of treating MDR-TB can be 1 000 times more than treating standard TB. Extensively drug-resistant (XDR) TB occurs when there is resistance to all of the most effective TB drugs. It is defined as TB with MDR, as well as resistance to any of the fluoroquinolone drugs, and to at least one of the three injectable second-line drugs (amikacin, capromycin and kanamycin). XDR emerges through mismanagement of MDR-TB and can also be spread from person to person.

A limiting factor to testing conventional defences against the spread of airborne TB is the inability to quantitatively culture human-generated airborne bacteria from the air under real-life conditions because of low concentrations and competing environmental organisms. The Airborne Infection Research (AIR) facility, launched in 2005 at the HJE Schultz SANTA Centre in Witbank, Mpumalanga, was designed to address this problem. 

The culmination of a five-year research project by a collaborative team from the CSIR, the Medical Research Council, Harvard University and the Centre for Disease Control and Prevention (CDC) in the USA, the AIR facility involves extraction of infectious air from patient wards to exposure chambers that house guinea pigs, which serve as living quantitative samplers of human-generated TB. Parsons, as the engineering research member of the collaborating research team, was responsible for all architectural engineering aspects of the research behind the design, development, operation and, in part, the bio-aerosol sampling techniques.

The engineering sophistication of the facility enables the development of scientific blueprints for the design of safer healthcare facilities. “The various engineering interventions necessary to curtail the transmission of infection, such as upper-room ultra-violet germicidal irradiation and other electro or mechanical interventions, can now be tested and evaluated,” Parsons explains. 

This unique contribution to bio-aerosol science has been recognised by the Department of Health and Human Services, the CDC and the National Institute for Occupational Safety and Health in the USA through a contract awarded to Harvard to undertake various ground-breaking research projects at the AIR facility over a period of five years, commencing in 2007. - CSIR


February 2008