have learned that larger particles can move farther , especially with helpful directional airflow , and so finding particles and even live virus more than two meters from an infected patient doesn ’ t always mean that the virus is traveling or surviving in these tiny droplet nuclei . And similarly , the fact that most infections occurred after close contact does not always mean that it ’ s only through larger particles . The highest concentration of particles of all sizes are found nearer to the source , and distancing is still beneficial . We ’ ve learned that ventilation can have an impact . Good ventilation really can decrease concentrations across a wide size range of infectious particles accumulating in enclosed spaces . This is good for preventing super-spreader events in crowded spaces , but it won ’ t prevent a close-contact transmission from whoever you ’ re sitting right next to , even if there ’ s great ventilation .”
Babcock continued , “ So , where do we go from here ? What we have learned is that viral transmission in general is a very complex process and it involves an infected source on a susceptible host , but also the transport mechanism from that source to that host requires sufficient viral inoculum to cause infection and that can be affected by the viral burden in the source . In most U . S . hospitals and healthcare settings currently , there is pretty good ventilation , these facilities have frequent air exchanges and filtered air , plus monitoring of their systems . Healthcare , of course , is also a workspace , and so we must recognize risks from unprotected interactions that are different from our interactions with patients where we are more careful , specifically in our interactions in breakrooms where we are interacting in a more social environment .”
Regarding forging a better path forward , Babcock emphasized , “ I think it ’ s time for a possible refinement of healthcare usage of the terms ‘ droplet ’ and ’ airborne ’ — both are transmitted through the air , but perhaps the distinction should not be based primarily on the size of the infectious particle . The CDC ’ s Healthcare infection Control Practices Advisory Committee ( HICPAC ) is starting to work on a revision of the 2007 isolation policy guidelines and is considering better ways to describe what these risks are , as well as better ways to categorize what kind of precautions we should be taking .”
Babcock added , “ We also need better masks , as we have learned that the fit of masks matters and that isolation masks and some surgical masks that are not one-size-fits-all have more variability . Masks that fit our faces better will protect people better . I think we ’ ve also learned that isolation policy recommendations may need to be more nuanced . The time from symptom onset may be more important than whether a PCR test is still positive . And the use of equipment that decreases environmental spread maybe should be considered . There are several possibilities for how this might look going forward . I think it would be helpful in the future to separate the personal protective equipment recommendations from air handling recommendations , so perhaps going forward we would have PPE recommendations known as respiratory precautions . In general , a well-fitting isolation mask with eye protection would likely be sufficient , and this would cover most respiratory viruses , and would likely include SARS- CoV-2 as well . In terms of enhanced respiratory precautions , this
We also need better masks , as we have learned that the fit of masks matters and that isolation masks and some surgical masks that are not one-size-fits-all have more variability .” might be terminology we could use for other situations that are considered high risk and for pathogens that have been shown to follow what we currently call an airborne transmission pattern . These could be recommended for TB patients and for high-risk procedures where there is proximity , forced air and infected tissue that could pose an increased transmission risk to the healthcare worker . In those settings and situations , perhaps respirators then would be the appropriate PPE to be used , and air-handling recommendations could be made separately . Most respiratory viruses have not shown to spread over long distances within healthcare settings , and routine or neutral air handling would be sufficient ; negative pressure could be reserved for patients where it ’ s been shown to be important , such as for TB patients and measles patients .”
Babcock continued , “ In addition to new isolation guidelines , I think we ’ ve learned a lot about how well we can control respiratory viruses with some of the other measures that we ’ ve put into place during this pandemic ; patient masking for source control is something we may want to keep going forward , either targeted based on symptom screening or universal masking , which can be helpful during high transmission times or perhaps all the time for high-risk patient populations like oncology or bone marrow transplant patients . We may see in the future that for flu season every year , we use universal masking for healthcare workers and for patients . It ’ s remarkable how controllable flu might be with some of these other interventions in addition to vaccination . Eye protection is increasingly being accepted as a standard part of respiratory precautions , and that will probably be maintained . The benefits of active symptom and exposure screening for patients and visitors as well as for employees can help minimize risk and encourage appropriate use of precautions . Many of the interventions we put in place during the pandemic should be maintained for the support and care of our providers going forward . An open question is whether ‘ aerosol-generating procedure ’ as a term is still a useful paradigm . If so , we need clarity that an aerosol generating procedure is not anything that Increases particles so that breathing or talking is not considered an aerosol-generating procedure . That doesn ’ t provide any discrimination for us in terms of thinking about when we need enhanced precautions , so perhaps ‘ high-risk procedure ’ would be a better term . In trying to determine what those procedures are , we should consider the risk of an increased concentration of infectious particles , possibly increased distance of spread during procedures that move air forcefully from likely infected areas in the patient into the environment . As we work through that , we ’ ll need to decide whether personal protective equipment recommendations then would be based purely on the procedure or the procedure and the pathogen , or what combination would be appropriate for the best protection .”
Babcock emphasized that vocabulary is less important than a focus on interventions , and that “ when vocabulary gets in the way of communication , we need to change their vocabulary so that our communication can be clearer , and so that our interventions can be well defined . Hopefully we can incorporate what we ’ ve learned this year into our formal guidance and planning for future events going forward .”
www . healthcarehygienemagazine . com • december 2021
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