The Washington Post website features 4 fascinating epidemic simulation scenarios. At that site you can observe simulated epidemic spread of a contagious respiratory disease like Wuhan Coronavirus — under 4 distinctly different conditions. The first simulation illustrates how an epidemic might spread with no restrictions on human interaction or distancing from one another. The second simulation depicts an attempt at total quarantine of all infected. The third simulation shows the effect of moderate voluntary “social distancing” on epidemic spread. The fourth simulation shows the effect of greater social distancing — with most social and commercial venues either shut down or severely restricted. You can run the simulations yourself
A graphic summary of all four simulations is presented below over a several week/month timeline:
- The “Free for All” scenario displays a tall, steep, rapid accumulation of infected cases, with a relatively rapid recovery for most.
- The “Attempted Quarantine” graph displays multiple peaks of infection within the extended outbreak, which tends to last longer than in the Free for All scenario — as the quarantine is broken by multiple infected cases.
- The “Moderate Distancing” simulation displays a prolonged outbreak with lower peaking at a later time — and a long tail.
- The “Extensive Distancing” simulation reveals a prolonged — but very low intensity — outbreak, that infects a much lower proportion of the population.
None of the approaches above can be considered optimal solutions. The first simulation results in an overwhelming of medical resources — with many deaths likely in the population and among medical personnel, depending on disease virulence. The second simulation has much the same result as the first, when the quarantine fails. The third simulation somewhat mitigates the impact on medical resources by “flattening” the infection curve a bit — but it extends the duration of the outbreak. The fourth simulation spares medical resources, but extends the outbreak into future seasons — and the cost to society in loss of wages, loss of earnings, and loss of social fulfillment can be greater than the cost of infection, if the virulence of the infectious agent is relatively low. That is why we institute minimal restrictions on movement in the case of most seasonal flu — and no restrictions at all are used in most other seasonal respiratory viruses.
Note that “herd immunity” is high after epidemic scenarios one and two, albeit with significant damage to the medical infrastructure when it is overwhelmed by cases.
If virulence is high and there is a good chance of developing viable treatments/vaccines before the next likely virus season, then simulation 4 is the winner, hands-down. If virulence is low (Case Fatality under 1%) then a variation of simulation 3 combined with intensive testing of suspected infections and self-isolation of infected might involve less economic damage. That is the approach that South Korea has taken in response to its unexpected rapid infusion of the China virus, direct from Wuhan.
Interesting Analysis of the Wuhan Virus Global Pandemic
The discussion below attempts to use the specific characteristics of the particular virus, in an attempt to take a measured and balanced approach to containment measures.
Before undertaking containment efforts of any kind, decision-makers need to look carefully at several issues:
- Laying-off workers, even for a short time, severely adversely affects the economy.
- The expected length of delay in cases made possible by quarantines is likely to be very short, sometimes lasting not much longer than the quarantines themselves.
- We seem to need a very rapid improvement in our ability to treat COVID-19 cases for containment efforts to make sense, if we cannot stamp out the disease completely.
Because of these issues, it is very easy to overdo quarantines and other containment efforts.
In order to completely stop its spread, we would need to separate each person from every other person, as well as from possible animal carriers, for something like a month. In this way, people who are carriers for the disease or actually have the disease would hopefully have time to get over their illnesses. Perhaps airborne viruses would dissipate and viruses on solid surfaces would have time to deteriorate.
This clearly could not work. People would need to be separated from their children and pets. All businesses, including food sales, would have to stop. Electricity would likely stop, especially in areas where storms bring down power lines. No fuel would be available for vehicles of any kind. If a home catches fire, the fire would need to burn until a lack of material to burn stops it. If a baby needs to be delivered, there would be no midwife or hospital services available. If a person happened to have an appendicitis, it would simply need to resolve itself at home, however that worked out.
… The big issue with containing the coronavirus is that we cannot really tell who has it and who does not. The tests available for COVID-19 are expensive, so giving the test to everyone, frequently, makes no sense. The tests tend to give a many false negatives, so even when they are given, they don’t necessarily detect people with the disease. There are also many people who seem to spread the disease without symptoms. Without testing everyone, these people will never be found.
… The number of reported COVID-19 cases to date is tiny, compared to the number that is expected based on estimates by epidemiologists. China reports about 81,000 COVID-19 cases to date, while its population is roughly 1.4 billion. If epidemiologists tell us to expect 20% to 60% of a country’s population to be affected by the end of the first year of the epidemic, this would correspond to a range of 280 million to 840 million cases. The difference between reported cases and expected cases is huge. Reported cases to date are less than 0.01% of the population.
We know that China’s reported number of cases is an optimistically low number, but we don’t know how low. Many, many more cases are expected in the year ahead if workers go back to work. In fact, there have been recent reports of a COVID-19 outbreak in Shenzhen and Guangzhou, near Hong Kong. Such an outbreak would adversely affect China’s manufactured exports.
Italy has a similar situation. It is currently reported to have somewhat more than 10,000 cases. Its total population is about 60 million. Thus, its number of cases amounts to about 0.02% of the population. If Epidemiologist Lipsitch is correct regarding the percentage of the population that is ultimately likely to be affected, the number of cases in Italy, too, can be expected to be much higher within the next year. Twenty percent of a population of 60 million would amount to 12 million cases; 60% of the population would amount to 36 million cases.
… Is it possible to reduce overall wage loss and deaths by using quarantines? This approach works for diseases which can actually be stopped through isolating sick members, but I don’t think it works well at all for COVID-19. Mostly, it provides a time-shifting feature. There are fewer illnesses earlier, but to a very significant extent, this is offset by more illnesses later. This time-shifting feature might be helpful if there really is a substantial improvement in prevention or treatment that is quickly available. For example, if a vaccine that really works can be found quickly, such a vaccine might help prevent some of the illnesses and deaths in 2021 and following years.
[Discussion of “Herd Immunity”]
Let’s suppose that 55% would need to catch the COVID-19 to allow the population immunity to rise to 50%. The virus would likely need to keep cycling around until at least this percentage of the population has caught the disease. This is not much of a decrease from the upper limit of 60% during the first year. This suggests that moving illnesses to a later year may not help much at all with respect to the expected number of illnesses and deaths. Hospitals will be practically equally overwhelmed regardless, unless we can somehow change the typical seasonality of viruses and move some of the winter illnesses to summertime.
It is very easy to believe that if some diseases can be subdued by quarantines, the same approach will work everywhere. This really isn’t true. We need to be examining the current situation closely, based on whatever information is available, before decisions are made regarding how to deal with the COVID-19 outbreak. Perhaps any quarantines used need to be small and targeted. __ Gail the Actuary
Understanding the infectious agent helps immensely when devising counter-measures. Unfortunately, China has not been forthcoming in sharing its early experiences with the Wuhan Coronavirus — and is still censoring information from health care providers who were involved at the frontlines in Hubei province.
It is easy to see why many policy-makers were hopeful that the virus could be contained using basic quarantine measures. But this is not the Coronavirus they were looking for. It is not a virus that wants to be contained. It spreads very early in an explosive manner, before symptoms are clear or pronounced. It defeats ordinary quarantines.
If every country took the Chinese approach of “total shutdown,” as it did for Hubei, economies would be destroyed around the world. This might well result in more total loss of population well-being in the long run, than letting the virus run its course under conditions of moderate social distancing, widely-available testing, and self-isolation of the infected.
Everything depends upon the combination of infectiousness plus the general level of virulence. Those things are crucial to know, plus the stage of infection at which the agent can be reliably detected. In addition, we must know whether reliable treatments are available, and whether a reliable vaccine will become available within a helpful time period.
So far, there are no perfect solutions that can be applied to all populations. The pandemic is still evolving, and will continue to do so over the next year, at least. Don’t imagine for a moment that your country is out of the woods. Not even China is out of the woods. Only Wuhan has any kind of herd immunity at this time.
Avoid unnecessary travel or large gatherings. Discover cultural alternatives to handshaking.
They want you to panic, and run to Costco to vainly search for toilet paper and sanitizers to hoard. But you will not give them that satisfaction, will you?
Here are two simple epidemic simulators —
Plug in 3 parameters and run. It seems to be preset with an average mortality rate of around 0.2% (up to 20% mortality for the oldest). You set the initial number of infected, the “attack rate,” and the duration of illness/contagion.
This simulator has 12 settings including death rate, attack rate, duration of illness, time to contagion, population, etc.
This CDC website lets you play the disease detective in order to solve a number of outbreaks.
You can find more realistic epidemic simulations online, but the learning curve can be steep for the best ones.
The best approach to the epidemic at hand — the Wuhan Coronavirus — is the approach that brings you out on the other side in good condition physically, financially, and emotionally.