COVID-19: IMPORTANT HIERARCHIES

Easing lockdown in England has released activities in groups in an order based on a risk assessment.  This reflects:

• Indoors more risky than outdoors
• Risky to have extended period of proximity to others, hence the need for social distancing

There's also a hierarchy of transmission, with microdroplets carrying viruses (commonly referred to as "aerosols") believed to be the biggest cause of infection:

• Through the air
• Microdroplets (aerosols), hence the use of fabric masks to catch them
• Droplets
• Floating viruses
• By touch, having touched a surface coated with viruses
• Touching mouth or nose
• Touching eyes 
• Touching open wound, perhaps

From that we can infer a hierarchy of where protection is needed, starting with the highest:

• In the home with family, which studies have shown as being responsible for more than 50% of all transmission
• On public transport
• In workplaces where distancing is difficult, in rest rooms and/or where the work is carried out
• etc

This is supported by this study of outbreaks in China in January and February: 

• "Home outbreaks were the dominant category (254 of 318 outbreaks; 79·9%). Most home outbreaks involved three to five cases
• Followed by transport (108; 34·0%)
• We identified only a single outbreak in an outdoor environment, which involved two cases.
• All identified outbreaks of three or more cases occurred in an indoor environment, which confirms that sharing indoor space is a major SARS-CoV-2 infection risk."

Odd then that there's been little if any advice about reducing the risks of catching the disease from family or housemates. 


ACTIVITIES

Here is a list of activities compiled by doctors in Texas, assessed by level of risk.  Presumably not listed is a score of "10" for "Living with someone infectious": 

A HIERARCHY OF ACTIVITIES

It struck me that we could usefully display activities in a hierarchy where the activities are grouped by risk level, and the size of the area somewhat reflects the size of the risk.  This is just a first draft sketch, but worth developing and refining.  The "No Risk" section is to highlight any activity has a degree of risk, however slight:

At a glance, it is clear what activities are highest risk and:

• Either need to be avoided, such as eating inside a restaurant when possible to eat outside, or
• Unavoidable, so suitable precautions need to be taken

The same principle can be used in any risk assessment, of say a school or an office.