Have we improved the contact tracing?

Selamat Hari Raya AdilFitri to our Muslim friends.  

It is instructive to note that the DG of MOH is going to spend his first day at the hospital. I would have thought that his time is better spent worrying about testing and contact tracing since this is going to be our main arsenal in the fight against the virus.

I have always worried about our contact tracing capability.

During the early days of the MCO, the contact tracing performance has been very bad as can be seen from the table below.  This shows how the virus has spread from the index case(s) to the subsequent generations for the 5 main clusters that arose either pre-MCO or the early days of the MCO.  You will notice that in many cases the virus has spread to the 5^th generation before it dies out.  If you consider that the sickness lasts for about 2 weeks, 5 generations of transmission meant that we still had infection for these clusters 3 months after the index case.

The worst part is that even today we are still getting cases in the Tabligh cluster. 

Item	Tabligh	Church	Case 26	Wedding	Italy
	Number of cases for the respective clusters
Index population	16,000	NA	NA	NA	NA
Index cases	1,037	1	1	1	1
1st generation cases	1,143	1	25	30	1
2nd generation cases	921	22	19	40	5
3rd generation cases	220	43	1	12	25
4th generation cases	26	29	0	3	6
5th generation cases	12	14	0	8	3
Past 3 days cases	12	0	0	0	0

Source: Malaysiakini

BTW, clusters are identified after some time and on 19^th May, 972 cases were re-classified to be part of the Tabligh cluster.  So there was a jump in the cumulative number of cases from 2,375 cases the day before to 3,347.   I track cases by districts and I have also noticed occasional changes to numbers due to counting or classification errors. To be fair I don't know whether this is due to MOH or the news media. 

Moral of the story – don’t rely on daily figures.  Look at trends.

There is no generation information yet for the many current clusters e.g. the several residential areas in KL under EMCO, the Market cluster.  To get a sense of how well contact tracing has improved, I compared the cumulative number of cases for some of the more recent clusters as shown below.

Cluster	1st reporting (a)		2 weeks later (b)	6 weeks later
	Date	No of cum cases	No of cum cases
Madrasah Sg Lui	12th April	90	158	198
Selangor Mansion	12th April	75	167	179
KL Wholesale market	6th May	181	200	Still early

Source: Malaysiakini

Note

a) We assume first reporting as the index case(s)

b) The duration is approximate as I do not have records on the number of cases on the exact date.

Looking at the number of cumulative cases for Sg Lui and Selangor Mansion clusters, I would guess that they have gone to at least the 2^nd generation.

• For the past 10 days, there have not been any new cases reported for the Selangor Mansion cluster so I hope that this is the end of the infection for this cluster.

• However, there were still cases from the Sg Lui cluster on 22^nd May so expect more from this cluster. However, on the positive side, the pace of increase has slowed down as in the first 2 weeks we had 68 additional cases whereas from the 2^nd to 6^th week, we only had 40 additional cases.

If the data on the above 3 clusters are representative of what is happening to the other more recent clusters, we should give MOH a thumbs up as it would point to an improvement in our contact tracing.  However, I would prefer a more definitive generation report by cluster from MOH.

I am not sure how many appreciate the scale of the contact tracing challenge. 

• Yesterday I mentioned this lady in Kelantan who caused 30 of her family members to be tested.  This is not the end of the story and MOH is still tracing the friends she visited.  So it is a minimum ratio of 1:30 of case to contacts.  (Refer to What is the implication of a 3:1 ratio)

• The Tabligh event had 1,037 index cases from 16,500 participants.  But MOH had tested 40,613 by19 May.  This is a ratio of 1:39

• For the Market cluster, MOH traced 37,133 by 17 May.  Imagine that this started with about 30 cases from the Selangor market around the 3^rd week of April.

So do your part to help contact tracing:

• Register when you visit places
• Download MyTrace
• For those holding “close house” for Raya, record your visitors as I am sure you will not remember who visited you 14 days ago. 
• Better still, stay at home. 

Selamat Hari Raya

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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.