John Massey is an engineer, not a medical professional. But he is smart, interested and well read, and he has a solidly fact-based worldview from a Hong Kong observation point. So I think his information is worth sharing, not least to avoid unnecessary fears. Bottom line: it’s not the end of the world.
Infection: By droplets from coughing or sneezing (max. range about 2m) which can hit you in the eyes, nose, mouth and infect you that way; picking up virus from surfaces (fomites, where it can stay alive possibly for weeks) and then touching the mouth, nose, eyes, where the virus enters through the mucous membranes; direct contact with infected people (shaking hands, kissing, whatever); in at least some circumstances (maybe when the disease has progressed in an infected person to infect their lungs) by airborne transmission (aerosols when people breathe out, so much greater range than droplets, and it can spread through ventilation ducts, central air-conditioning systems, etc.) It is at least as easily transmissible as seasonal influenza, maybe more so.
Incubation: Anywhere from 2 to 14 days (and in a few cases seemingly a lot longer), during which people are asymptomatic but already infectious, so disease control becomes really difficult, particularly combined with aerial transmission. In that scenario, trying to trace all ‘close contacts’ of infected people to identify those who might be infected and quarantine them all becomes an impossibility. But still worth doing, because taking some of those people out of circulation for 14 days quarantine will help to reduce the rate of spread of the virus. The problem then becomes – where do you put them all to keep them in quarantine? Home quarantine becomes an option, but then some people will sneak out, abscond, need to get out to buy food and other essential supplies. But all quarantines leak, they always do, but still worth doing to slow down the rate of spread.
Asymptomatic: Some people remain asymptomatic and recover naturally, but are still infectious while they have virus in their bodies.
Mild: Fever, dry cough, sneezing.
Severe: A % of mild cases will progress to severe, when people begin to experience breathing difficulty – if this is going to happen, it seems to happen about 5 days after the first onset of symptoms (but evidently what takes about 5 days in China is happening in a matter of a few hours in Iran, so it looks like the virus has mutated there to become more virulent), when the virus infects the lungs, and people need supplemental oxygen to keep them alive long enough while they recover from the infection.
Critical: A % of severe cases will progress to critical, where people need intensive support like mechanical ventilation to keep them alive.
Death: A % of critical cases will result in death.
Iran: Worryingly, in a lot of informally reported cases, people have suffered permanent damage to the heart muscle – the whatever, the myocardial muscle. The big pump.
Everywhere: In all severe and critical cases everywhere, some people suffer permanent lung damage.
So, imagine two scenarios: Scenario A and Scenario B.
In Scenario A, public hospitals receive new cases at a rate they can cope with and have sufficient resources to provide the necessary level of medical care, while ensuring that medical staff have sufficient personal protective equipment (masks, eye shields, plastic body suits, etc.) to avoid being infected themselves. Scenario A is what has happened in all areas of Mainland China + Hong Kong + Macau except for Hubei Province. In Scenario A, the fatality rate seems to be around 1%, so about 10x the typical fatality rate for seasonal influenza, which is around 0.1%.
In Scenario B, public hospitals are overwhelmed by being presented with so many cases that they do not have the resources to cope, have only enough beds and can only provide the necessary medical support for the more severe cases, and they do not have sufficient PPE for medical personnel, so a % of them also become infected and some die. This is what has happened in Wuhan (where the case fatality rate has been around 5%) and to a lesser extent in the rest of Hubei (where the CFR has been around 3%), and 3.8% of medical personnel have become infected.
When do you have an epidemic? When you have locally self-sustained transmission of the virus, with an R0 > 1. R0 is the average number of people that one infected person can infect. For SARS-CoV-2, it is working out at about 2.8 on the Chinese data, but you need to watch out for ‘super spreaders’, people who have the ability to shed a much greater viral load and infect many more people, and there have been some of those. R0 is not a constant, and if you can get R0 < 1, the epidemic will die out.
Testing: Difficult, because the early symptoms look like seasonal influenza or a bad cold, so there will be far more suspected cases than confirmed cases. The test developed for it is genetic matching from nasal and pharangeal swabs, you need 3 consecutive tests spaced a day apart to avoid false positives and false negatives, and the test is proving to be imperfect – some people who initially test negative go on to infect others, and then test positive later.
Recovery: The criteria that the Chinese are using, which are pretty solid, are 2 consecutive negative tests + no fever for 10 consecutive days + improving lung scans. But worryingly, some people who have recovered and have been discharged have subsequently infected some others, so now China is quarantining all recovered and discharged cases for a further 14 days.
China: Guangdong, the second most severely affected province, but still a very long way below Hubei, the epidemic has peaked and died down to close to zero, and they have downgraded their health alert from I to II – I think only Guangzhou and Shenzhen are still locked down, Shenzhen hasn't had a single new known infection for days now, and everywhere else everyone is back at work, but schools remain closed – so in Guangdong they have done a super job; well done, people. Hubei, the epidemic is still going strong but seems to be peaking (which it will at some point – all epidemics peak at some point), and they have started to ease some of the controls on people's movements. Wuhan has been much harder hit than anywhere else in the country. Everywhere else in China seems to have peaked and be on the way down.
South Korea: exploding and in very deep shit.
North Korea: reports daily that they still have zero cases. Believe that and you will believe anything. Anecdotal reports that they are burning bodies like crazy.
Japan: exploding, maybe not quite as bad as South Korea, where it is running wild in the armed services and everywhere, but still a very worrying situation.
Italy: starting to explode. They are trying to control it aggressively by locking places down, canceling all of the football matches (you know things are bad in Italy when they cancel the football) and all of the other sensible stuff they can do, but it still looks like they could be in for a bad time, particularly with their aged population.
Iran: officially, not bad – the Ayatollahs are censoring the news, and everything is pretty much OK. Informally, via anecdotal reports from doctors and others in Iran, it is exploding all over the country, and the virus seems to have mutated there into a much more virulent strain; very high numbers of infection, very high deaths. Really bad. Major disaster.
Indonesia: Thinks it has no cases, but then it has no test kits, and no health care system to speak of. They could have a raging epidemic and not know it. That could apply to a lot of African countries too – lots and lots of Chinese people coming and going to various African countries, so it defies belief that none of them have any of it. Ethiopia still has regular commercial flights to China – they must be out of their minds.
USA: The CDC is sensibly on high alert and actively doing what they can to prepare, getting extra equipment, PPE, etc. The biggest risk to the USA is Canada, which is being run by an idiot. Yes, a worse idiot than Trump, if that's possible.
UK and Australia: The governments keep saying they are well prepared, when they are not remotely – if they get an epidemic, they are screwed, they will be straight into Scenario B.
HK: 74 known cases so far with 2 deaths, so already far fewer than Italy. The local epidemic curve, such as it is, has died right down and we are only getting the occasional small trickle, but some people keep doing dumb things like going to church or the local Buddhist centre or having big group dinners. But people are paranoid and panic-stricken, and the atmosphere is anxiety inducing. The known infection rate so far is 0.001% of the population, so I can't take seriously the idea that we have something you could call an epidemic, but we need to stay careful. By this stage in 2003, with the SARS epidemic (which I suppose I now have to call SARS-CoV-1) we had more than 1,000 infected and 50 deaths, and by the time it burned itself out at the start of summer we had 299 deaths. This could be potentially a lot worse, but so far the reality is far better. So far.
The Diamond Princess cruise ship anchored in Yokohama: Don't want to talk about it. Complete shit-show. If you want to read about the whole dreadful debacle, you can Google it. In short, Japan has earned itself widespread international condemnation for the way it has grossly mishandled the whole dreadful mess, and also condemnation from some of its own very experienced infectious disease control specialists.
Vaccines: none yet, and even if they can find one, it will take about 2 years to test, mass-manufacture and vaccinate everyone, so forget that. I don't want to sound gloomy, but no one has yet managed to find a vaccine for SARS or MERS.
Treatments: none yet, but some individual reported successes with some antivirals, and with plasma from blood taken from patients who have recovered, which has antibodies against the virus (this is far from a new idea, and seems to be quite promising). But they all need proper trials, which will take at least months. In the meantime, the best they can do is just keep you alive long enough for your body's immune system to fight off the virus.
Who dies: Mercifully, not kids, not even newborns whose immune systems are not fully developed, and not healthy young people. Most at risk of dying are older people, and/or people with pre-existing health conditions like chronic heart disease, diabetes, hypertension, respiratory illnesses. And more men than women, both because of smoking patterns in China (half of all men smoke, while fewer than 2% of women do) and because women generally have somewhat better disease resistance. If you are over 80 and have some prior health condition (which almost everyone does at that age), you are basically screwed, but then at that age you are not going to be around for a hell of a lot longer anyway. If you are over 70, you have about an 8% chance of dying, but worse if you have one or more of the above health conditions (assuming Scenario A, not Scenario B).