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Federal Register / Vol. 86, No. 116 / Monday, June 21, 2021 / Rules and Regulations CDC, May 7, 2021.
In general, enclosed environments, particularly those without good ventilation, increase the risk of airborne transmission CDC, May 7, 2021; Tang et al., August 7, 2020; Fennelly, July 24, 2020. In one scientific brief, CDC
provides a basic overview of how airborne transmission occurs in indoor spaces. Once respiratory droplets are exhaled, CDC explains, they move outward from the source and their concentration decreases through fallout from the air largest droplets first, smaller later combined with dilution of the remaining smaller droplets and particles into the growing volume of air they encounter CDC, May 7, 2020.
Without adequate ventilation, continued exhalation can cause the amount of infectious smaller droplets and particles produced by people with COVID19 to become concentrated enough in the air to spread the virus to other people CDC, May 7, 2020. For example, an investigation of a cluster of cases among meat processing employees in Germany found that inadequate ventilation within the facility, including low air exchange rates and constant air recirculation, was one key factor that led to transmission of SARSCoV2
within the workplace Gunther et al., October 27, 2020. An epidemiological investigation of a cluster of COVID19
cases in an indoor athletic court in Slovenia demonstrated that the humid and warm environment of the setting, combined with the turbulent air flow that resulted from the physical activity of the players, allowed COVID19
particles to remain suspended in the air for hours Brlek et al., June 16, 2020. A
cluster of cases in a restaurant in China also suggested transmission of SARS
CoV2 via airborne particles because of little mixing of air throughout the restaurant Li et al., November 3, 2020.
Infections have been observed with as little as five minutes of exposure in an enclosed room Kwon et al., November 23, 2020. Outdoor settings i.e., open air or structures with one wall typically have a lower risk of transmission Bulfone et al., November 29, 2020, which is likely due to increased ventilation with fresh air and a greater ability to maintain physical distancing.
For more discussion of this subject, see the Need for Specific Provisions Section V of the preamble on Ventilation.
Transmission of SARSCoV2 is also possible via contact transmission both direct contact as well as surface contact, though this risk is generally considered to be low compared to other forms of transmission CDC, April 5, 2021. Infectious droplets produced by
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an infected person can land on and contaminate surfaces. Surface, or indirect, transmission can then occur if another person touches the contaminated surface and then touches their own mouth, nose, or eyes CDC, April 5, 2021. Contact transmission can also occur through direct contact with someone who is infectious. In direct contact transmission, the hands of a person who has COVID19 can become contaminated with the virus when the person touches their face, blows their nose, coughs, or sneezes. The virus can then spread to another person through direct contact such as a handshake or a hug.
The risk posed by contact transmission depends on a number of factors, including airflow and ventilation, as well as environmental factors e.g., heat, humidity, time between surface contamination and a person touching those surfaces, the efficiency of transference of virus particles, and the dose of virus needed to cause infection. Studies show that the virus can remain viable on surfaces in experimental conditions for hours to days, but that under typical environment conditions 99% of the virus is no longer viable after three days Riddell et al., October 7, 2020; van Doremalen, April 16, 2020; CDC, April 5, 2021. At this time, it is not clear what proportion of SARSCoV2
infection are acquired through contact transmission and infections can often be attributed to multiple transmission pathways.
In recognition of the potential for contact transmission, CDC recommends cleaning, hand hygiene, and, under certain circumstances, disinfection for helping to prevent transmission of SARSCoV2 CDC, May 17, 2020; CDC, April 5, 2021. These are long established recommendations to prevent the transmission of viruses that cause respiratory illnesses Siegel et al., 2007.
The potential for contact transmission was demonstrated in one study that reviewed cleaning and disinfection in households Wang et al., May 11, 2020.
The study found that the transmission of SARSCoV2 to family members was 77% lower when chlorineor ethanolbased disinfectants were used on a daily basis compared to use only once in two or more days, irrespective of other protective measures taken such as mask wearing and physical distancing. For more discussion of this subject, see the Need for Specific Provisions Section V
of the preamble on Cleaning and Disinfection.
These methods of transmission are not mutually exclusive, and each can present a risk to employees in
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healthcare settings. Based on these methods of transmission, there are a number of factorsoften present in healthcare settingsthat can increase the risk of transmission: Indoor settings, prolonged exposure to respiratory particles, and lack of proper ventilation CDC, May 7, 2020. First, and most significantly, healthcare employees in settings where patients with suspected or confirmed COVID19 receive treatment may be required to have frequent close contact with infectious individuals, these settings are typically not designed for physical distancing, and many areas in these facilities are not ventilated for the purpose of minimizing infectious diseases capable of droplet or airborne transmission.
Employees frequently touch shared surfaces and use shared items. Even in healthcare settings where employees have their own offices or equipment, they often share a number of common spaces with other workers, including bathrooms, break rooms, and elevators.
Based on these characteristics, SARS
CoV2 appears to be transmissible in healthcare environments, a conclusion supported by existing data Howard, May 22, 2021. COVID19 incidence rates have increased significantly for adults of working age as the pandemic has progressed in comparison with other age groups, with researchers noting that occupational status might be a driver Boehmer et al., September 23, 2020. Currently, case rates continue to be predominantly higher in working age groups in comparison to children and those over the age of 65 CDC, May 24, 2021.
Given the high transmissibility expected in healthcare environments, the exposure risk that employees face is high. This risk is related to some extent to viral prevalence, which refers to the number of individuals in healthcare settings who may be infectious at any moment. As explained below, current data indicates that viral prevalence in the population is based on a number of factors, including the viruss existing reproductive number, the prevalence of pre-symptomatic and asymptomatic transmission, and the recent documentation of mutations of the virus that appear to be more infectious.
The transmissibility of viruses is measured in part by their reproductive number or R0. This number represents the average number of subsequently-infected people or secondary cases that are expected to occur from each existing case, which includes low transmission events as well as super-spreading phenomenon.
Thus, an R0 of 1 indicates that on average every one case of infection will
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