The growth of the ‘novel coronavirus’ (there was no official name at the time of my previous post) has been largely as projected in my previous post on the topic. At that time just over two weeks ago the virus had no official name, and while cases have grown from 4,000 to almost 70,000, these cases are still a consequence of ‘tipping point1: the Wuhan wet market‘. Since then there have been reports of two potential tipping points
- Avoiding Tipping Points?
- Reaching tipping points
- tipping point3: Westerdam?
- tipping point 2: Grand Hyatt Singapore Conference?
- japan cruise ship
- tipping point 1 again
- How bad can it get?
Avoiding Tipping Points
Cases outside ‘infected zones’, which is anywhere outside China so far, that are detected early and where it is believed all those in contact with cases of the disease can be traced and quarantined, add to the global count of cases, but do not lead to new outbreaks of the disease in new territories.
If a all cases outside China are detected and quarantined soon after arrival, then the epidemic could be restricted to within China.
Arrivals from an identified ‘infected zone’ can be screened, allowing for the early detection.
The goal of every country is to keep any cases within the ‘infected elsewhere’ category, or at least to the ‘infected from a known source with all other potential infections screened’.
Reaching tipping points?
When a case occurs in an area or country that results in contact with too many people for quarantine of all possible new cases to be feasible, a tipping point is reached. The result can be a new area or country with that experiences a repeat of Wuhan. New infections where all contacts of the source of infection being screened is no longer possible. Thus a tipping point in the saga of Covid-19 is an event that could result in a new significant zone of uncontrolled spread of the virus. First tipping point seems to have been the wet market in Wuhan, see below. This may have resulted in the spread throughout the province and pontentially all of China.
So to be clear, a tipping point for a country or territory is an infection that occurs within the territorty from a source that cannot be identified, or not all contacts with that source can be contacted and screened.
tipping point3: Westerdam?
This raises concerns over not just the 400 who arrived on the same flight from Cambodia to Malaysia, but on the other passengers on the Westerdam. There are reports further confirmation of the diagnosis is required, but it confirmed, then the number of people potentially exposed makes this in practical terms a potentially uncontainable outbreak. Note that the same article that states that confirmation of the case is still required, counts the case as part of ‘confirmed cases within Malaysia’.
It was stated that all onboard had been continually tested during the two week voyage of the Westerdam, with no passengers testing positive, but the ship had been turned away by Japan, Taiwan, Guam, the Phillipines and Thailand, which suggests some lack of confidence that there was certainty all passengers were clear of infection.
A number of Dutch citizens who were aboard the Westerdam have already returned to the Netherlands, where they will be monitored daily by local health authorities.straits times
“Already returned” suggests these passengers travelled and arrived believing they had the ‘all clear’, so how many people have been in contact with these passengers?
There were 1,455 passengers and 802 crew abort the Westerdam, who all passed tests both at sea and in Cambodia. Having tested negative, it would seem logical that all 2,257 would have had normal level of human contact since disembarking. But as would appear to have been aboard another cruise ship, the Diamond Princess, passengers who are initially though to have the all clear, can be later diagnosed positive. It is not clear why screening does not always work , but it casts doubts over whether all given the all clear, are indeed ‘all clear’.
This event not only creates potential a tipping point for Cambodia, due to contact with disembarked passengers and crew, but for any country where an infected passenger has returned and not had all contacts tracked.
The fact that one person from the ship now has the virus, it seems logical there was at least one infected passenger on board from the outset. Given the cruise ship environment and what has been seen on the Diamond Princess, this would mean at the very least 10 infected passengers at disembarkation. Not just one. Where are the others?
tipping point 2: Grand Hyatt Singapore Conference
The Westerdam may not be the first case of a group containing some people exposed to the virus, who then dispersed internationally.
This ‘itpping point 2’ seems to a least correspond with what is looking more like an early outbreak in Singapore, but can lead to outbreaks in other countries triggered by returning conference delegates.
The Diamond Princess.
Another cruise ship, the diamond Princess, has been the most significant outbreak outside Chian so far. With current 286 cases from less than 4,000 passengers, it is well below the threat of spread to a new country and, at least at this stage, it is believed all cases have been quarantined without being released as carriers. However the outbreak on board the ship has been the best chance for those outside China to learn about the behaviour of the virus and how it spreads.
tipping point 1: Wuhan Wet Market
Just to review tipping point one. It is thought that many viruses cross from animals to humans, but then they stop because
It is not known for certain if the first time Covid-19 crossed to humans was at the market or not, but what is known is that almost all the initial cases visited the market as a point of infection.
Within 3 months, infections reached almost 70,000 with over 1,600 confirmed deaths.
Either of the tipping points 2 or 3 could result unidentified sources of spreading the diseases arrving in more countries around the world, just as initiall happened with cases from China. But more importantly, it shows the potential of such cases to breakthrough to cause new outbreaks.
The list of cases internationally I found at this time is here. Asia, which interestingly in the list included Australia, has just over 300 cases outside China. North America 22, Europe less than 50 and the only other cases in the UAE.
In fact, almost all cases outside of Asia, are where the actual infection occured elsewhere, and a traveller arrived already infected with virus.
Certainly no epidemic outside Asia, so not a pandemic at this time. The tipping point events 2 and 3 certainly point to a very high probability of further spread through Asia, which then makes containment within that continent very unlikely. In other words, reaching a pandemic seems most likely. Not definite, but likely.
How Bad Can It Get?
A pandemic sounds bad. The 2009 ‘swine flue’ pandemic killed 18,000 people, but did not exactly seem like the end of the world. Covid-19 could result in as few as less than 6,000 deaths even if it reaches pandemic status. However, such a total is more the opposite of how bad can it get.
With a 2% mortality rate, if every human on Earth contracts Covid-19, the death toll would be 150 million, but clearly, even in environments like the cruise ship Diamond Princess, it seems there are more cases where onre partner of a couple is infected than where both are infected. So if no vaccine is ever found, no real way of limiting the spread, the death toll could reach 75 million. More realistically, disease modellers estimate between 550,00 and 4.4 million, which means between 10,000 and 88,000 deaths. At either of these extremes, the global impact will be huge. And, since that modelling, I feel Westerdam has raised the worst case even further.
I will follow with further thoughts on the impacts of the these worst scenarios.