not just forward from source generation and infectious particle characteristics, such as their concentrations, size and aerobiological properties,” he said.“ There is also no suggestion that to mitigate the risk of shortrange airborne transmission full‘ airborne precautions’ should be used in all settings, for all pathogens, and by persons with any infection and disease risk levels where this mode of transmission is known or suspected.”
Taking the con perspective in the presentation,“ Clinical Evidence and Risk of Confusion Suggest No Need for Changing Fundamental Principles of IPC,” was John Conly, MD, FRCPC, a professor in the Department of Medicine at the University of Calgary in Alberta, Canada, who reminded attendees that as context,“ COVID was the first major pandemic in the modern age of instant social messaging, and the mainstream and social media were in overdrive. This created social media echo chambers and not very civil discourse, even among scientists. It was one of the most polarizing events in modern history, with highly emotional and often diametrically opposed viewpoints around non-pharmacological interventions, vaccines, and modes of transmission.”
Conly emphasized getting back to the basics.“ We have the chain of infection, and we all teach this in epidemiology and infection control,” he said.“ Then we’ ve got breaking the chain of infection. Keep it simple. There are many descriptions from epidemiologic literature and abridged by various disciplines to meet their needs; it’ s been understood for decades and is very sensible. The core split is direct versus indirect; direct route from reservoir to host and indirect route via and intermediate step reservoir to host. There may be a predominant mode of transmission and those of lesser importance in the usual natural settings. There are situational settings and circumstances which modify the natural
mode of transmission that must be taken into context. A pathogen may exploit multiple modes of transmission. Thus, identifying modes of transmission and modifying influences allow for optimal mitigation and prevention measures.”
He pointed to an outbreak of Mycobacterium chimaera in heater-cooler units used for extracorporeal circulation during surgery( Schreiber, et al. 2016).“ This was airborne transmission from the heater-cooler unit in a plume that dropped onto a sternal wound. To my knowledge, in this new document from WHO, they equate inhalation to airborne, but here’ s a fallacy in that document— I don’ t think a chest wound can inhale an organism, so that’ s one point of confusion. The other is that vehicles can refer to food, water, fomites and some people include air as well, so just to make note of that. They use‘ through the air” as a descriptor; they equate unequivocally airborne transmission to inhalation. They also use the term‘ not through the air,’ which is redundant and a potential point of confusion.”
Conly next pointed out that the“ new” terminology is not new to the clinical community.
“ A Canadian public health document from 2008 shows that‘ transfer of particles through the air’ was already in the nomenclature, the‘ continuum’ was already in the nomenclature, and was already well-recognized,” he said.“ People keep saying‘ inhaled respiratory droplets’ is a new term that has been coined, but I would argue that no, it’ s just a retooling of something that’ s been in the literature for two decades. Respiratory infectious particles instead of infectious respiratory and all the issues around size were already published in 2008 and 2014 in Canada and in the United States in 2007. In 1996, researchers used‘ through the air,’ which again, is not a new concept, it’ s been there for two decades. They also talked about the unresolved issue of the distance of 3 feet but for practical
ICPIC 2025, a bi-annual meeting, was held at the Centre International de Conferences Geneve( CICG) in Geneva, Switzerland, Sept. 16-19, 2025. Photo by Kelly M. Pyrek purposes it was there and always taught in the background in IP & C that you have to recognize this continuum. So, in my mind, much of it’ s not new and this is akin to the‘ old wine in a new bottle’ metaphor, not really new terms for the IP & C community. The other thing is equating of inhalational to airborne has created confusion because there are many non-inhalational modes of through the air or airborne transmission.”
Conly continued with his criticism of the WHO terminology document:“ I thought there was short shrift given to environmental transmission via the airborne route, such as with legionella, group-based strep, MSSA, MRSA, P. aeruginosa, Coxiella, atypical mycobacteria, Aspergillus, hantavirus, smallpox, HSV and others. There’ s a lot of focus on COVID and measles but in infection control we deal with the full gamut of diseases, not just a refined group.”
He pointed to the problems that the new terminology introduces related to AI-facilitated searches by clinicians.
“ Another point of confusion will be individuals who use AI and the definitions that are delivered,” he noted.“ According to the AI functionality through Google,‘ through the air’ is the old‘ droplet’ and‘ airborne’ transmission combined.‘ Inhalation’ is the new‘ airborne’ and‘ direct deposition’ is the new‘ droplet.’ HICPAC, which has been disbanded, was going to use the new terminology and then they came up with routine air precautions, special air precautions and extended air precautions. And then the transmission-based precautions and enhanced barrier precautions in nursing homes. It’ s now in limbo. So, there are so many terms being used now, and clinicians will get overwhelmed.”
He emphasized that better staff training and education is warranted.
“ I think we need to do a better job of how we teach clinicians.” Conly said.“ We can eliminate the redundancies and confusing terms. Fixing the mistakes and inefficiencies of a failed change plan is very time-consuming and damages credibility. If the benefits of these terminology changes are not obvious and sensible, then they breed resistance to adoption among healthcare workers, and it can also cause unnecessary friction, and there is the risk of fragmented acceptance across countries, and perhaps even reputational damage to the WHO.”
Conly outlined the practical issues for IP & C education and policy:
● Understanding of the continuum of IRPs and“ through the air” is already recognized for many years by IP & C
● Focus on core IP & C principles for mitigation, not new terminology
● Avoid overreaching changes – keep it simple
● Education of healthcare personnel is a
16 • www. healthcarehygienemagazine. com • nov-dec 2025