Why has the COVID‐19 pandemic generated such global interest from the engineering community?

This Special Issue mainly focuses on investigating and reinforcing the role of aerosol transmission of SARS‐CoV‐2 as the predominant driver of the COVID‐19 pandemic. Both modeling and experimental methods are widely used.

In particular, various studies have examined the potential for virus transmission in a variety of hospital (INA‐21–11–630.R1; INA‐21–04–235.R2; INA‐21–04–199.R1) and non‐hospital, community‐based settings—including people's own homes (INA‐22–01–037; INA‐21–12–687), cars and taxis (INA‐21–09–507.R1; INA‐22–01–023.R1), subway (INA‐21–08–430.R1) and surface train (INA‐22–01–018) carriages, cable cars (INA‐22–01–025), classrooms (INA‐22–01–014; INA‐21–11–610.R1), courtrooms (INA‐21–04–227.R1), and even an orchestral setting (INA‐21–12–663.R1).

Several papers also examine the impact of various mitigation strategies, including masks (INA‐21–03–147.R1; INA‐21–09–493.R2; INA‐21–08–465.R1; INA‐21–08–430.R1), social distancing (INA‐21–11–656.R1; INA‐21–03–147.R1; INA‐21–09–493.R2; INA‐21–08–465.R1), dividing screens (INA‐21–06–361.R1), portable air filters/cleaners/purifiers (INA‐22–01–037; INA‐22–01–014), and ventilation (INA‐21–09–493.R2; INA‐21–08–465.R1; INA‐21–08–430.R1).

Unlike previous recent epidemics of novel emerging pathogens: avian A/H5N1 influenza since 1997 ¹ and A/H7N9 since 2013, ² pandemic influenza A/H1N1 in 2009, ³ MERS‐COV‐2 since 2012, ⁴ West African Ebola since 2013, ⁵ Zika virus since 2014 ⁶ —why has the COVID‐19 pandemic generated such global interest from the engineering community?

There are several possible reasons for this. Firstly, the nature of the COVID‐19 pandemic (by definition) is global, with SARS‐CoV‐2 spread to all populations worldwide—rather than just being limited to a few, like avian influenza (mainly in East/Southeast Asia), MERS (mainly the Middle East), Ebola (most recently West and traditionally Central Africa), and Zika virus (most recently South America, and previously outbreaks in Oceania).

The 2009 influenza A(H1N1)pdm09 pandemic spread very quickly across the whole globe (within 6–8 months), and was relatively mild. ⁷ By the time any investigations were completed as to the mode of transmission, the global pandemic response had already moved to a mitigation approach. ⁸ In fact, the pandemic strain of A(H1N1)pdm09 soon replaced the existing seasonal A(H1N1) which actually came with a significant clinical benefit as the pandemic virus was sensitive to the commonly prescribed antiviral drug oseltamivir (Tamiflu), whereas the seasonal virus had already become resistant. ⁹

The second reason is that the relatively slow progression of the COVID‐19 pandemic and its high severity have given time and motivation for engineers to respond with their innate expertise in developing and applying methods to both understand how the virus was spreading and how to control it—including their expertise in HVAC (heating, ventilation, and air‐conditioning) systems. This also fostered many mutually beneficial new collaborations with clinical, microbiological, epidemiological, and public health colleagues. The unprecedented and devastating impact of the COVID‐19 pandemic on almost all aspects of human civilization has clearly motivated all scientific disciplines to contribute, including engineering.

Thirdly, it rapidly became clear that this virus was not spreading via traditional contact and droplet transmission modes, but more likely via an airborne ‘aerosol transmission’ route. One of the contributed articles outlines, historically, how the concept of aerosol transmission became side‐lined in clinical infection control thinking (INA‐21–11–634.R1).

In contrast, engineers learn about the fundamentals of airflows and aerosol transport that underlines aerosol transmission as undergraduates. Therefore, once it became clear that this virus was causing severe disease, and spreading mostly via aerosols, together with its relatively slow spread (due to its longer incubation period and generation time, as compared to pandemic influenza) across the globe, this gave engineers an opportunity to develop and implement mitigation measures and influence national recommendations and guidance within a time‐frame that could still substantially slow the spread of the virus—particularly to more vulnerable members of the population.

However, the mechanics of aerosol transmission and its impact in complex, crowded indoor spaces—in both hospitals and communities—have been very difficult to convey to the medical and public health professionals, who often advise on or govern pandemic responses.

Some engineers have been working in this cross‐disciplinary field since or even before the 2003 SARS outbreaks and have forged useful and influential collaborations with medical and public health professionals to the extent that they can influence their local or national policy.

Although international health bodies like the World Health Organization (WHO) now accept the predominant role of aerosol transmission of SARS‐CoV‐2 and the benefits of improved ventilation to control its spread, ¹⁰ this was not the case during the first year of the pandemic. ¹¹

Various modeling studies have also indicated that the earlier implementations of non‐pharmaceutical measures to take this into account (e.g. universal masking, social distancing, enhanced ventilation, and local or national lockdowns) could have saved tens of thousands of lives. ¹² , ¹³ , ¹⁴

Such models have also highlighted the impact that the resistance—often acrimonious and sometimes aggressive—by some members of the medical profession to accept the concept of aerosol transmission has been not just wrong, but detrimental and rather shameful, particularly in the face of rapidly evolving evidence to support aerosols as the predominant mode of transmission. ¹⁵ , ¹⁶ , ¹⁷

With such Special Issues such as this one, let us hope that a more collaborative and mutually respectful, cross‐disciplinary approach to dealing with future pandemics will be the norm rather than the exception.