Here's the best layman's summary I can assemble on the current virus, with the reliable information currently available. This has a focus on the otherwise-healthy over-50s, your typical allotment holder. "???" indicate the unknowns, of which there are still quite a few. With this many unknowns, I doubt very much if we can trust computer-model -based forecasts. Updated with new information: 10th March
* Fatality rate:
In China the initial fatality rate was 1.3% across all 50-somethings.
But that was the epicenter, where it all started, and there one has to consider that...
1. the provincial Chinese have a worse heathcare system that we do, and that will have had a cumulative effect on the health of the population and especially on older people;
2. many older Chinese may have compromised lungs due to decades of living in their really bad air pollution and smogs;
3. heavy drinking and smoking is also much higher there, especially among older men.
These three factors may, partly, explain why the figures show Chinese men were found to be very slightly more susceptible to the virus.
* Pre-existing conditions:
In China pre-existing serious disease seemed to "increase risk of dying by 2.5 times". These being diabetes, heart disease, cancers, etc.
In China the "fatality rate in patients who reported no other health conditions was 0.9%".
But one UK doctor told the Daily Mail yesterday... "We're probably missing this iceberg of milder cases", thus making the % death rate seem higher than if everyone were counted. This seems like good news, but there is debate among scientists on this point. It partly depends on if you believe the Chinese statistics and think that that they have been able to track it successfully. The World Health Organisation monitors have been there and they think the robust measures taken by the Chinese have been successfully tracking all cases, more or less.
19 strains of the virus are reported to have been genetically sequenced in China. Apparently it is still mildly mutating and adapting, as is perfectly normal for such a virus. According to WHO worldwide cases are still "spillover" from the epicentre, where it started, rather than new epicenters arising from new mutant strains.
In the UK the official advice yesterday was "The virus is spread through droplets which come out of people's lungs. These may be coughed into the air and then inhaled, or transferred into the eyes, nose or mouth after getting onto someone's hands." and "The virus can enter the body through the eyes, nose and mouth, but not through the skin."
Scientists think that hand transmission is far more common and far more likely than casual/fleeting air transmission of droplets from a stranger coughing and sneezing near you, hence the strong urging to wash our hands and not touch face, eyes or nose.
Partial airborne transmission via droplets appears to need close and sustained contact? And exposure needs both sustained duration and many droplets, so that you breathe in a sustained infectious dose. This method of transmission looks very probable, but is not confirmed — partly because it would be so difficult to ethically do the controlled studies. Top world experts who visited China, such as Bruce Aylward of WHO, reportedly kept six feet away from anyone who could be a 'contact' for the virus, but he wore no mask. That seems a good distance to keep in mind.
And what the infectious dose is... is also unknown, but it must be quite low given the speed of spread. Does the load of the 'infectious dose' mean 'a heavy dose = a worse case'? Again, unknown?
There is limited evidence we can pass it to dogs by snuffling closely with them, but they can't then pass it back us??? Definitely not confirmed yet.
* Masks and gloves:
The science on previous virus-spread shows that face masks may prevent someone spreading the virus when sneezing or coughing, but not prevent getting the virus from casual contact. Also, masks and scarves slip, and apparently these slips encourage people to adjust the mask straps and thus brush their face with their fingertips and hands.
Gloves are therefore more important than masks. How important, exactly? Would fingerless gloves also help? Unknown???
Good 30 second handwashing, as is being widely advised, reduces the risk of catching the virus. But by what % does it reduce the risk? By 100%, if done properly???
Is it also wise to wash the face and hair, after coming back home and first washing one's hands and wrists thoroughly? Unknown???
* Survives on surfaces:
Yes, according to the UK Chief Medical Officer. The virus can survive in hand-smears on doorknobs, rails etc. Indeed on all "hard metal or plastic surfaces", for "as long as three days". It is "largely gone by 48 hours and almost completely gone by 72 hours on a hard surface". Presumably phones, tablets and touchscreens are all affected.
Should tap surfaces also be well-sluiced with soapy water, after one's hand washing, without touching the taps again? Unknown???
Does all sealed hard-surface food packaging need to be washed in warm soapy water, on getting the shopping home? Unknown??? Presumably one would wear washing-up gloves while doing this, and try to not to splash droplets onto kitchen/bathroom surfaces.
Does Dettol help? It works well against other coronavirii. Not a myth. The company tests such things. It's only good for disinfecting surfaces and fabrics though, and in baths, as it seems there's not yet any way to make it safe for some sort of use inside the human body.
Symptoms can be anywhere from 2-14 days after catching. Outside Wuhan 97.5% are showing symptoms within 11.5 days, which suggests 14 days is a useful but not infallible yardstick for self-isolation after known exposure. The average time to show symptoms, outside Wuhan, is five days. What limits or speeds up the development of personal symptoms? The factors on this seem to be unknown at this stage???
The "typical signs include a runny nose, a cough, sore throat and a fever (high temperature)." With the nose probably less runny than in a normal cold/flu. The UK Chief Medical Officer has said that "the vast majority of patients will recover from these without any problems, and many will need no medical help at all."
How long do symptoms last on average, for an otherwise healthy adult over 50? Unknown??? At a guess it probably varies by person, type of self-care, warmth, stuffiness of the air, gender, previous nutrition levels, etc.
Chances of one's symptoms progressing to become a "Severe" case seem to be 7%, outside the world's hot-spots? Note here that "Severe" does not = death, for those who are healthy. As a medical category "Severe" appears to mean you have a nasty flu-like infection and there's cause for concern that it might suddenly turn dangerous, re: shortness of breath and the need for oxygen.
But how does that 7% break down across age groups and healthy/already-ill people? Presumably the already-ill and over 75s have a higher chance of it progressing from a "mild cold" to "Severe"? And the already-healthy have a lesser risk of progressing to "Severe"? Unknown???
It can be as long as five weeks between initial infection and death? More likely three, for most? Unknown overall duration, at present??? Again, this probably varies per person.
How long after recovery is one "safe" to go out and about, and not risk infecting others? What it the % risk of relapse? Unknown???
That's the best summary I can do at the present, with the best information available. For 50-somethings who take suitable and regular precautions and who are mostly at home and not gregariously social or in regular close contact with outside visitors, the risk of catching it seems negligible, perhaps less than 1%. The chances may be even less in some remoter parts of the country, such as rural Staffordshire.
If one does then somehow get it the chance of it becoming in some way "Severe", in an otherwise healthy non-smoking 50-something, might at an educated guess be 3 to 5%. At which point one's life-chances will then all depend on getting speedy medical diagnosis and aid. People are being advised not to do this by going to the doctor's surgery or to hospital, but rather to stay in their homes, and use the phone.