The Coronavirus Outbreak in Japan

In my first comments on the Coronavirus outbreak within my essay “Social Cohesion: The Best Vaccine Against Crises” which I published two weeks ago, on 3 February 2020, I stated my belief that the virus had already escaped the biosecurity net and that a global pandemic was, unfortunately, likely. I stated that the characteristics of the virus – its relatively long incubation period with asymptomatic transmission – made it very challenging to contain, and that the true cost to humanity would be determined by how virulent it proves to be. And finally I suggested that it would first be introduced to neighbouring countries, and that especially in developing countries it would likely spread rapidly due to the socioeconomic realities of their populations.

Then in my first regular update on the coronavirus outbreak on 9 February I mentioned that the situation on the Diamond Princess would bear close watching as we would get an excellent indication of transmissibility and pathogenicity of the virus under what might be considered optimal conditions – for the present – for detecting and treating infections.

In that same report I detailed what I had managed to gather from the ships schedule published online, but I was in the dark on the details of the first known infected passenger on the ship. All I knew was that the passenger disembarked at Hong Kong before the ship sailed onwards making stops before being placed in quarantine at Yokohama. The Wall Street Journal journalists have now followed up and have provided a reasonably detailed history for that passenger which I include below along with a handy map showing the passage of the ship from the moment the first known infected passenger boarded the ship up until it went into quarantine.

But firstly I will give a brief overview of the situation in Japan.

Background: Why is Japan Important to Watch?

Japan is important to study for a few reasons. It is the closest highly developed country to the outbreak, with very significant movement of people between the two countries.

Unsurprisingly that included movement between the city at the centre of the initial outbreak, Wuhan, and broader Japan as can be seen in the figure below taken from an early paper by Salazar et al (2020), epidemiological researchers out of the Harvard TH Chan School of Public Health, which looked at the number of reported cases relative to the volume of air travel between that country and Wuhan. Now the case data, of course, is well out of date, as the epidemic is moving so quickly, but what I really want the reader to note is the X axis which shows the average daily number of passengers travelling from Wuhan to other countries. Note that Thailand receives by far the greatest volume of passengers from Wuhan, but Japan is second.

Secondly, Japan is a highly developed country with a sophisticated health system, and its people enjoy a high standard of living which affords them a high underlying health state. Observing case fatality rates here should provide an indication of what is likely to be the situation in other highly developed nations, perhaps a few weeks in advance of the progression of the outbreak in countries receiving less movement of people from the initial site of the outbreak.

Up-To-Date Information on Cases in Japan

In recent days there have been several reports of seriously ill people infected with the coronavirus that have not travelled to China and have not had any known contact with people who have.

On 15 February The Japan Times detailed three separate cases unrelated to travel to China. One cluster of infections was around a hospital in Wakayama Prefecture where 2 doctors, one of their wives, and two patients were found to be infected. Another cluster occurred in Tokyo where 7 people infected by the virus travelled in the taxi of another infected person. An eighth Tokyo resident, a businessman who travelled on a bullet train while unwell, was also found to be infected. And a husband and wife in Nagoya were found to be infected shortly after returning from a holiday in Hawaii.

Health officials are now concerned about being swamped by people concerned that they are infected by the coronavirus and have released recommendations on when and how to access health services. The fact that seasonal flu and cold viruses will also be circulating complicates matters.

Below I will track the Japanese case data reported in the WHO Situation Reports released daily.

  • For 17 February: Confirmed cases 59 (3 new); Total cases with possible or confirmed transmission outside of China 33 (6 new); Total deaths 1 (0 new)
  • For 18 February: Confirmed cases 65 (6 new); Total cases with possible or confirmed transmission outside of China 39 (6 new); Total deaths 1 (0 new)
  • For 19 February: Confirmed cases 73 (8 new); Total cases with possible or confirmed transmission outside of China 42 (5 new); Total deaths 1 (0 new)

The Diamond Princess Case Study

This history is directly from the article Fear and Boredom Aboard the Quarantined Coronavirus Cruise Ship in the Wall Street Journal published 14 February 2020.

The first known infected passenger, an 80 year old Hong Kong man, boarded on 20 January at Yokohama (there are no details on how he got to be in Yokohama, though the story says that 10 days prior to embarking he travelled to Guangdong). He boarded with 2 daughters and they had a sauna while onboard.

At the first stop in the Kagoshima the man joined a bus tour with 40 other passengers. When the ship docked in Hong Kong, the man left the ship earlier than planned and 5 days later he went to hospital.

Route for Diamond Princess from 20 January 2020 when first known infected person embarked at Yokohama through to when the ship entered quarantine near Yokohama on 3 February 2020. The portion of the route in yellow designates that the first know infected passenger was onboard. From the Wall Street Journal.

After Hong Kong, the ship made stops in Chan May and Ha Long Bay in Vietnam, in Taiwan and in Okinawa (Japan) before going into quarantine in Yokohama on 3 February. The WSJ article details some of the tours that took place while in Vietnam.

Commencing 5 February passengers remaining on board the vessel have been restricted to their cabins in order to restrict the opportunity for transmission between those remaining on board. However, unfortunately one of the shore team that was assisting has also become infected. It is difficult to understand what proportion of the passengers that are now being found to be infected by the virus have contracted the infection after the quarantine period began. Evenso, the possibility of infection must have been significantly reduced by these quarantine procedures, so very many of the infected passengers must have been infected prior to quarantine commencing.

Below is a daily synopsis of events since the Diamond Princess entered quarantine on 5 February with 3,711 passengers.

  • 5 Feb – +10 – 10 confirmed cases, 31 tested
  • 6 Feb – +10 – 20 confirmed cases, 102 tested
  • 7 Feb – +41 – 61 confirmed cases, 273 tested
  • 8 Feb – +3 – 64 confirmed cases; 279 tested
  • 9 Feb – +6 – 70 confirmed cases; 336 tested
  • 10 Feb – +65 – 135 confirmed cases; 439 tested
  • 12 Feb – +40 – 174 confirmed cases; 492 tested (4 people in intensive care)
  • 13 Feb – +44 – 218 confirmed cases; 713 tested
  • 14 Feb – +4 – 222 confirmed cases
  • 16 Feb – +67 – 289 confirmed cases
  • 17 Feb – +66 – 355 confirmed cases; 1,210 tested
  • 18 Feb – +99 – 454 confirmed cases
  • 19 Feb – +92 – 542 confirmed cases (2,404 test – 169 infected passengers still on ship)
  • 20 Feb – +79 – 621 confirmed cases

A few things are clear from the 2 weeks that the Diamond Princess has been in quarantine. Firstly, it is clear that the virus indeed is highly transmissible. The first known infected individual was onboard for only 5 days, and the vessel continued on for just 8 days more until it entered quarantine. While cruise ships are known to be environments where viruses are quickly spread between passengers, this is clearly a highly transmissible virus.

Secondly, this case is beginning to suggest that the incubation period and time to morbidity and mortality is reasonably prolonged, which I suggested in my initial reports, thus making biosecurity containment challenging.

This case bears very close watching and I will be updating this page daily.

Now that most countries are transporting home those that did not exhibit symptoms and/or tested negative for the virus, it may be challenging to put together exactly what happens with this cohort of people. Nonetheless reporting will likely mention the origin of these cases and I will do my best to put it all together here.

The US took home their citizens first. There was a hickup as only uninfected individuals were to be on the flight, however on transit to the plane it was learned that 14 in the group had tested positive. They were allowed to join the group and sat separately on the plane, which is a common sense approach as it is highly likely that there will be more infections found amongst those who tested negative (and there may be some who were not tested prior to flying in any case who are not yet showing symptoms). The Centre for Disease Control in the US has stated that all people who were passengers on the ship should be tested for the virus.

On 20 February NHK released that 2 Diamond Princess passengers in their 80s had died from the coronavirus infection.

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© Copyright Brett Edgerton 2020

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