I've no intention of giving my opinion with respects to the should / shouldn't we cave debate, however I thought I would make some comments regarding containment and contamination as that might inform others trying to decide. Without going into details, I work with very hazardous materials and hence spend a lot of time dealing with containment & contamination issues.
First thing to note, it is more or less impossible to 100 % contain anything and hence any containment strategy and subsequent contamination is dealt with as a risk based approach. Secondly, meeting high levels of containment and hence very low contamination is a highly skilled activity which the general public are not competent to achieve. So please don't kid yourselves into thinking the risk is zero if I do xxx.
In the case of COVID19, the hazard is basically the virus contained in droplets of bodily fluids (typically saliva). I'm no virologist so not prepared to comment on whether blood, urine etc. are also a hazard in this case. Is there anyone else on here who can?
The risk is defined as a combination of the severity of the hazard and the likelihood of it being realised. A containment strategy looks to reduce both.
1. The severity can be reduced by all the good things scientists around the world are working on (vaccinations, cures / treatments) and those being conducted in hospitals presently (having sufficient beds, ventilators, oxygen, trained staff, etc.). Unfortunately there is little the general public can do to help with this one (other than perhaps not unnecessarily take up hospital beds).
2. Reducing the likelihood of coming into contact with contaminated bodily fluids is where we can help...
The first thing to look at is how we could come into contact with the virus:
1. Absorption having touching a contaminated droplet. Fortunately our skin is an amazing barrier and hence absorption through it can be ruled out in this instance.
2. Inhalation - breathing in an aerosol of contaminated droplets. This is the issue with being in confined spaces (e.g. trains / buses) when an infected person coughs. You share the air they expel. The higher the density of people in a given area the greater the likelihood of exposure via this route.
3. Subcutaneous - injecting the virus / it entering the body via an open wound. Well I hope we're not injecting this virus and I hope our caves do not contain contaminated needles, however cuts and grazes down a hole can occur. This cannot be entirely ruled out as it's possible (albeit remote in my opinion) that you could cut yourself on a sharp rock that was also contaminated with the virus and hence it enter the body through this route.
4. Ingestion - again with any luck we're not going around licking up other peoples bodily fluids (or at least not down caves), however this is an issue with regards to secondary transfer. This is the issue of touching a contaminated surface and then licking your fingers / picking your nose / eating your sandwiches.
So as cavers we need to think about 2,3&4.
The first and most effective thing we can do as individuals is reduce other peoples likelihood of coming into contact with contaminated surfaces or air by isolating in our own homes if we are infectious. There is the obvious problem here that many people are infectious whilst asymptomatic and currently testing on demand before we leave home is not possible. Numerous unusual symptoms are being reported worldwide including things like loss of taste / smell and hence for recreational activities perhaps we should be considering staying home if we've got any unexplained ailments beyond those listed in the current government advice? Obviously due to the asymptomatic issue, isolating those with the virus is not as effective as we might like and hence those who are not infected or do not think they are infected also need to help. In terms of caving, as a starting point, if we resist from dribbling, spitting, coughing, sneezing, taking a pee etc. we are reducing the likelihood of contaminating the environment around us which we are sharing with others.
Getting back to routes of exposure...
First consider inhalation. This is complex. Some caves have airflow, some are static, some humid, others dry. Most containment strategies in the workplace involve controlling air flows and hence you could argue the person at the drafting dig face is significantly safer than those behind. In all reality, the best thing we can do without studying and controlling the factors above is not cough / sneeze on each other and generally keep a distance such that we are not breathing what others exhale. Obviously any decision whether to cave or not needs to consider whether this is possible. Personally I can think of caves it is and others it is not.
Second, the subcutaneous issue. This is easy. Clothing provides a good barrier to getting cuts / grazes and as cavers we're typically covered in it. Gloves is the obvious addition which some cavers don't use to protect the hands. Beyond that we're all used to the 'cover & clean any open cuts and grazes with respect to advice relating to weil's disease. That also applies in this instance.
Finally ingestion. I'll start with lets not lick the formations somebody's spat on. More seriously, as cavers we're probably some of the best members of the general public to prevent the secondary transfer discussed in point 4 above. Typically we do not touch our faces, put fingers in mouths, eyes, etc. as our hands are covered in mud / grit and at heart were a vain bunch really and don't like dirty faces. Assuming we're wearing gloves, as cavers we're pretty good at removing these before doing any of the above should we need to. If we wear gloves when touching potentially contaminated surfaces (i.e. what somebody else has breathed / coughed on) and then remove them in such a way to keep our hands clean before touching our faces, eating etc. then we're actually demonstrating really good practice. Best thing we can do is remember do not get mud in your mouths, up your noses, in your eyes. It probably goes without saying, sharing drinks, chocolate etc. would be stupid. We know washing hands is the most effective way of removing the virus by the mechanical action of flowing water. This would apply to surfaces as well so any being washed by running water would clean quicker than those that are dry and hence reduce the likelihood of being contaminated quicker. Finally after caving washing hands before eating etc. as per government advice makes perfect sense. With clubs closed this is harder, but a bottle of water, towel & some soap in the car this is easily dealt with.
I'm not going to consider the longevity of the virus outside of a host as although differing surfaces and conditions are known to effect this, the reported time frames seem to be hours to a few days and hence for the duration of a normal caving trip (hours) we must consider surfaces remain contaminated.
Apologies for the long posting - hopefully it was worth my time writing it out.