WHO terms pathogens that transmit through air ‘infectious respiratory particles’ or IRPs

WHO introduces term 'infectious respiratory particles' for pathogens transmitted through the air, ending terminology challenges during pandemics.

Pathogens that transmit through the air will be described by the term ’infectious respiratory particles’ or IRPs, according to the World Health Organization (WHO). The world health body has thus ended the lack of a common terminology to describe the transmission of these pathogens, which was particularly challenging during the global COVID-19 pandemic. The announcement on Thursday came following wide-ranging consultations across multiple steps in 2021-2023.

“The challenge became particularly evident during the COVID-19 pandemic as experts from various sectors were required to provide scientific and policy guidance. Varying terminologies highlighted gaps in common understanding and contributed to challenges in public communication and efforts to curb the transmission of the pathogen,” the WHO noted.

The pathogens include those that cause respiratory infections, for example, COVID-19, influenza, measles, Middle East Respiratory Syndrome (MERS), Severe Acute Respiratory Syndrome (SARS), and tuberculosis (TB), among others.

In its communication, the WHO said that individuals infected with a respiratory pathogen can generate and expel infectious particles containing the pathogen through their mouth or nose by breathing, talking, singing, spitting, coughing, or sneezing, and these particles should be described with the term IRPs. Also, IRPs exist on a continuous spectrum of sizes, and no single cut-off points should be applied to distinguish smaller from larger particles. 

The WHO said this facilitates moving away from the dichotomy of previously used terms — ‘aerosols’ (generally smaller particles) and ‘droplets’ (generally larger particles).

The WHO has published a global technical consultation report introducing the updated terminology for pathogens that transmit through the air following consultations with public health agencies and experts. The publication titled ‘Global technical consultation report on proposed terminology for pathogens that transmit through the air’ is the result of an extensive, multi-year, collaborative effort, and reflects shared agreement on terminology between the WHO, experts, and four major public health agencies — the Africa Centres for Disease Control and Prevention, the Chinese Center for Disease Control and Prevention, the European Centre for Disease Prevention and Control, and the United States Centers for Disease Control and Prevention.

“Together with a very diverse range of leading public health agencies and experts across multiple disciplines, we are pleased to have been able to address this complex and timely issue and reach a consensus,” Jeremy Farrar, Chief Scientist, WHO, said. “The agreed terminology for pathogens that transmit through the air will help set a new path for research agendas and implementation of public health interventions to identify, communicate and respond to existing and new pathogens,” Dr. Farrar added.