The lockdown and vaccination have proved highly effective in reducing the impact the Coronavirus Pandemic but governments around the world continue to caution about the risk of complacency, the risk from new variants and the fact that the virus may become endemic.
To this end ongoing precautions will and must become the norm
The UK government has consistently relied on the science from two bodies namely SAGE (Scientific Advisory Group for Emergencies) and NERVTAG (New and Emerging Respiratory Virus Threats Advisory Group).
Many of the submissions from the scientists refer to the risk of infection from aerosols and below are some abstracts from their submissions, and links are provided to their full reports.
Key Message
Working in enclosed poorly ventilated spaces, such as consulting rooms, un-ventilated offices and individual bedrooms will still require mitigation against infection by aerosols. Medixair’s ability to provide an easily installed disinfection solution using safe Ultraviolet Light offers the community a solution to this problem. medixair.com
Role of Aerosol Transmission in COVID-19
SAGE Environment and Modelling Group
- The updated WHO guidance acknowledges that in poorly ventilated spaces, transmission through an airborne route cannot be ruled out. This is a notable change from previous guidance which indicated the virus was spread by droplet and contact transmission
- Based on the current evidence, it is possible that transmission through aerosols could happen where a person who generates significant amounts of virus is in a poorly ventilated space
- It is difficult to fully explain the level of transmission without considering that airborne routes are playing a part.
- Evidence to date suggests that poorly ventilated spaces pose the highest risk, so it is recommended that mitigation measures focus on those spaces where ventilation is absent or inadequate.
- Ventilation refers to provision of sufficient fresh (outdoor) air, while air conditioning is provided to control the temperature in a space. Building regulations and Health and Safety at Work legislation require adequate ventilation to be provided in all domestic, public and commercial buildings. There are large numbers of spaces across the breadth of UK building stock where the provision of ventilation does not comply with the building regulations.
- The use of recirculating air cleaners may be appropriate in small spaces where ventilation is poor and cannot be easily improved. Devices which use HEPA or UV-C are likely to be the most effective. There is limited high quality evidence for other technologies and some can pose a hazard (e.g. by introducing ozone).
NERVTAG – Evidence of environmental dispersion for different mechanisms, and the risks and potential mitigations/measures of control within different environments from what we know about COVID- 19:
A brief evidence summary for SAGE, 14 Apr 2020
- Air cleaning technologies including ultraviolet disinfection may be a viable approach for controlling fine aerosol particles, particularly in rooms with poorer ventilation.
- Potential for controlling exposure to respiratory aerosols
- Exposure to aerosols below 10µm diameter for those greater than 2m away will be dominated by the airflow conditions in the environment. While there will be some deposition of particles resulting in contact transmission risk, exposure through inhalation is likely to be the dominate risk, and their dispersion can be predicted with airflow models. The exposure will be determined by the rate at which aerosols are generated together with the rate at which they are diluted or removed by ventilation indoors or wind outdoors.
- Although close range exposure is widely thought to be dominated by droplets, laboratory and modelling studies [17][39] examining exposure (1-2m) to different sized particles suggests that
- inhalation exposure to fine aerosols (airborne risk) could be a more significant part of transmission than the direct deposition of droplets onto mucous membranes.