Is the Detainee cluster another Tabligh cluster?

I started my Covid 19 daily analysis sometime in March 2020 in an attempt to understand what was happening in Malaysia vis-à-vis how we are tackling the virus.  

Actually, it began when I watched the MOH briefing on what was happening particularly to the Sri Petaling event. I noticed that the reporters present did not ask pointed questions when I specifically had 2 in mind:

• Is the government testing the people who have come into contact with those who have been infected recently e.g. the Tabligh group? 
• Does the government have a Covid 19 infection model. If yes, what is the model projecting for the number of cases by the end of Mac.

After feeling that no one seemed to care about asking such questions, I figured that I better analyze the situation myself.  

I also shared my analysis with my former upper secondary school mates hoping that those with the medical or pharmaceutical background could provide some insights.  A couple of weeks ago, my son suggested that I should have a blog for these daily comments.  I laughed at the idea then cos I said that the posting would end soon as there would not be anything to cover once we won the Covid 19 battle.  Of course like all children, he did not listen to me and started to transfer those in May into blog postings.

Now I think I am wrong as it looks as Covid 19 would be with us for a much longer time.  I wake up every day to read about new issues and see more uninformative news reports.

We currently have a new cluster from those foreign workers under detention that saw a very significant spike yesterday. 

May            No of new daily cases

21                     34

22                     27

23                     21

24                     33

25                   112

On one hand, we have the NGO saying “I told you so” regarding the risk of infection by having the detainees be kept in a place where social distancing is difficult.  In return, we have MOH saying that those infected or at least the first batch were from those detained pre-MCO.

Since the signs of infection do not manifest immediately, the “I told you so” may not be supported by the data.  Then the mystery is how those detained pre-MCO managed to get infected since they could go out of the centre. One theory by MOH is that they were infected by the staff.  We will have to wait for more statements from MOH before we can get the true story.

With such a spike in the number of daily cases, the question is whether we are seeing another Tabligh cluster.  The chart below compared the growth in the number of cases within the first 5 days of both clusters.  You can draw your own conclusion about the pace of change.

Note:  The Tabligh event was in the early days of our virus experience so the daily number of cases due to the cluster was not reported daily. I had to triangulate it from several news sources and as such the daily figures may not be precise although the cumulative figures are more accurate.

There are of course fundamental differences between the Detainee cluster and the Tabligh one

• The Tabligh cluster resulted from the people attending the event in Sri Petaling.  They all disperse after the event and there was difficulty in contact tracing them.  On the other hand, the detainees are all confined to their respective detention centre making it easy to test all of them quickly.

• While only about 16,000 attended the Sri Petaling event, eventually MOH screened 41,200 people resulting in a ratio of 1 : 2.6 for the index population to final cluster screened size  Although the event was held at the end of Feb, there were even 8 new cases from this cluster on 25 May.  On the other hand, we would expect the final number of people in the Detainee cluster to be screened to be slightly higher than the original population size

As of yesterday, there are 4,742 people including staff from the 3 detention centres who have been tested with 227 positive cases to-date as can be seen from the table below.

Detention centre	Total tested	No positives	Positivity rate (d)	No waiting results
Bukit Jalil	1536 (a)	126	19.7 %	896
Semenyih	1,757 (b)	66  (c)	8.1 %	938
Sepang	1,449	36	6.3	873
Total	4,742	228 (e)	9.9%	2,704

Notes

a) 1,422 detainees, 114 staff

b) 1,630 detainees, 127 staff

c) 1 admin staff tested positive yesterday

d) No of positives divided by No tested (ie positives + negatives)

e) There is a discrepancy between the details provided ie 228 cases in total with the 227 total cases cited by MOH

MOH has warned that this is not the end of the number of infections among this cluster as there are 2,704 cases pending the test results. 

I estimated that the number of potential cases could vary from 267 to 291 cases depending on the assumptions made on the positivity rates (the former is based on the overall positivity rate while the latter is based on the rates of the individual centre). 

So expect high numbers for the next few days.  The unknown is whether there will be more detainees but this a question for the immigration dept rather than MOH.

I am not a public health staff nor am I associated with any NGO.  My concern is the risk to the community at large.  I don’t think the general public is going to visit the detention centre and hence there is no risk from this manner of transmission.  This is what MOH said as well.  Of course, the sick will be hospitalized and thus use the Malaysian medical resources but this is another story.

The only risk I see is those Malaysians whose work will require them to be in these detention centres.  They may then get infected (Index case DC) and then be a source of infection to the other Malaysians.

But as I have said in my 6 May posting,(Where does risk of infection comes from) the risk comes from 3 contagious groups:

a)      Those who don’t know they are sick ie the asymptomatic cases

b)      Those who don’t yet that they are going to fall sick ie those at the incubation stage

c)      Those who don’t care that they are sick i.e. afraid to seek treatment 

I think we can rule out the transmission due to (c) from any Index Case DC.  What about from sources of transmission from (a) and (b) then?

MOH is already testing all staff in the detention centres and I think they should also test and have other measures for all visitors to the detention centres.  If this is done, we will be able to catch the asymptomatic and those at the incubation stage. 

If we have bad luck, maybe some of the Index DC cases may pass the virus to their contacts before they are tested positive meaning there will be some spread but then our contact tracing protocol should kick in to control the spread.

Conclusion

1) The Detention cluster is going to be more limited in terms of index population to the final cluster size compared to the Tabligh cluster.  OK if you are a pessimist you can argue that there will be more foreign workers to be detained in the coming weeks and they could be potential new cases.  However,  it has been reported that the MAEPS in Serdang will be turned into a quarantine and treatment centre of the undocumented migrants so this could isolate those infected from new detainees. 

2) If I was to guess, I would say that the final Detainee cluster would be about 500 to 600 cases. Definitely not another Tabligh

3) It may be simplistic, but the main risk of spreading is some Malaysians being caught up as part of the Detention centre cluster.  If I want to be facetious, if you want to avoid risk you should avoid contact with any immigration staff or MOH staff assigned to the detention centres for the next couple of weeks.

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PS: This blog is for me to better understand COVID 19 as this will impact my investments. If you are also into equities, follow me at i4value.asia

Disclaimer:  I am not an epidemiologist, healthcare worker, pharmacist or staff in the Ministry of Health, but rather is someone with a strong interest in numerical analysis.  The content is an attempt to understand what is happening in the battle against Covid 19 from a data-based perspective. The opinions expressed here are based on information extracted from readily available public sources but I do not warrant its completeness or accuracy and should not be relied on as such.