should not be implemented in hospitals due to the high risk of fungal infections such as Aspergillus , Mucor , Rhizopus and others in immunocompromised patients . Outside air may contain these fungi , and there have been many , many outbreaks due to construction or renovation , and open windows . This recommendation might be practical in places such as restaurants and schools , but it is not something we should be doing in hospitals .”
Weber pointed to studies demonstrating true long-distance air transmission of pathogens such as varicella and smallpox , a characteristic which has not been demonstrated for SARS-CoV-2 .
“ In an outbreak of varicella , the index case was a 3-year-old with transverse myelitis and varicella pneumonia ,” he said . “ Out of 32 patients on the ward , 24 were found to be susceptible by serology . There were 15 cases of varicella , but none had exposure outside of the hospital . There were no air ducts connecting the rooms of the index patient and the cases , but the directional airflow studies show the risk of transmission was directly related to the airflow on the ward . Patients three or four rooms away from the index case acquired varicella ; outbreaks like this of COVID-19 have not been described .”
Weber continued , “ In a study of the airborne spread of smallpox , the index case was on the ground floor of the hospital with natural ventilation ; it spread to patients on the same floor as well as to patients on higher floors of the facility . This is a classic example of true airborne , long-distance transmission , which has not been demonstrated with SARS-CoV-2 ; the study also demonstrates that natural air may not protect against infection with a highly infectious disease that has environmental survival .”
Next , Weber pointed to an outbreak of COVID-19 at a large academic hospital . “ Healthcare providers had returned from vacation at a COVID-19 hotspot , and they worked together for a number of days . They were symptomatic while still working and then there was a pizza party held in a breakroom . As a result of that index case , there were multiple healthcare providers who became ill ; there was also transmission from 36 healthcare providers to 22 patients . The mechanism was failure of the healthcare providers to wear their personal protective equipment ( PPE ) and follow physical distancing guidelines . However , there was no transmission from these infected people other than direct exposure to infected healthcare workers and there was no transmission to floors above and below the breakroom , even though there was directional air flow from the infected patients ’ rooms ; again , demonstrating — unlike varicella and smallpox – a lack of long-distance transmission with SARS-CoV-2 .”
Weber briefly reviewed the familiar mitigation strategies for SARS-CoV-2 , such as vaccination , masking while indoors , and physical distancing , as well as frequent hand hygiene and surface disinfection , then turned to the topic of improved ventilation , achieved through improved filtration , increased air exchanges , as well as the use of devices that disinfect the air , such as ultraviolet devices inside air ducts .
Many studies demonstrate efficacy and effectiveness , and observation studies have demonstrated lower rates of infection in immunized healthcare providers .
Regarding universal masking , many studies in the lab setting show it is effective to reduce or eliminate expulsion of viable virus .”
“ As we examine those recommendations and those devices for improved ventilation , we must look at how we grade the evidence for implementation of infection prevention-related interventions — starting with animal and lab studies , moving to case reports , case control series , cohort studies , randomized controlled trials , and then meta-analysis systematic reviews leading to clinical practice guidelines ,” Weber said . “ Generally , we use the evidence most from randomized clinical trials and to a lesser extent , data from well-done cohort or case control studies . But before we implement any intervention in healthcare , we want to see evidence that the intervention achieves its designated purpose ; in this case , to mitigate SARS-CoV-2 .”
Weber emphasized that the Centers for Disease Control and Prevention ( CDC ) does not have specific recommendations regarding ventilation in hospitals for COVID-19 beyond what is already used , including airborne isolation rooms , special air handling in departments such as operating rooms , central sterile services , and sterile pharmacies , etc . “ The CDC does note that viral particles spread between people more readily indoors and that protective ventilation practices and interventions can reduce the airborne concentrations of the virus . What hasn ’ t been shown is whether doing this actually reduces the risk of people acquiring COVID in hospitals or in other venues . As well , the CDC does note the cost of these interventions ; there ’ s no cost for opening windows , of course , but as we emphasized , we would not do this in the hospital setting due to fungal risks . You could use fans if you had open windows , but again , this is not something we would do in hospitals . We could certainly add HEPA filters at about $ 500 a unit , and we could certainly add upper room ultraviolet disinfection devices at an approximate cost of $ 2,000 . Importantly , the CDC does not cite any references for these statements , and , of course , in hospitals we do use airborne isolation rooms for known and suspected COVID , as well as other airborne-transmitted diseases such as measles and tuberculosis .”
Weber emphasized that studies in healthcare facilities cited by the World Health Organization ( WHO ) as a rationale for the WHO ventilation guidelines are not adequate to assess the impact of improved ventilation for COVID transmission prevention .
Regarding the evidence for supporting COVID-mitigation strategies and healthcare facilities in general , Weber noted , “ Vaccination is important . Many studies demonstrate efficacy and effectiveness , and observation studies have demonstrated lower rates of infection in immunized healthcare providers . Regarding universal masking , many studies in the lab setting show it is effective to reduce or eliminate expulsion of viable virus . If you put a mask on the uninfected person , it protects them from inhaling particles or viable virus , and many observational studies and meta-analysis studies demonstrate the benefit . Physical distancing has been demonstrated in case control studies , observational studies , and meta-analysis , and we ’ ve already talked about measures such as distancing , hand hygiene , environmental cleaning and disinfection that are standard interventions for
www . healthcarehygienemagazine . com • december 2021
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