In numbers: The COVID-19 pandemic

Coronavirus | Patient data from Singapore and South Korea shows physical distancing is the only option

Spaced out Customers await their turn at specified distances to prevent the spread of COVID-19, at a grocery shop in Salem. SPECIAL ARRANGEMENT Specialarrangement

Spaced out Customers await their turn at specified distances to prevent the spread of COVID-19, at a grocery shop in Salem. SPECIAL ARRANGEMENT Specialarrangement  

In many countries, often all it took for the novel virus to spread was one infected person who didn't maintain physical distance

South Korea had just over 30 COVID-19 cases in the 28 days after it reported the first. But when contact-tracing was done for patient-31, a Pandora's box was opened. In the next 17 days, the number of cases crossed 6,000. Similarly, cases in Singapore would have been much lower if not for a dinner party. Infected persons in Kerala travelled to many places where people congregate before getting diagnosed. Essentially, all it took for the novel coronavirus to spread was one infected person who didn't maintain physical distance.

The Singapore clusters

As of March 23, Singapore has identified seven COVID-19 clusters responsible for 50% of its cases.

The graph plots cases in each such cluster. Each dot corresponds to a case. Close to 47 cases originated from a dinner party on February 15 at a restaurant in the Safra Jurong recreation club.

Which cluster in Singapore saw the most cases?

image/svg+xml 0 50 100 Patient number 150 200 250 300 350 400 Dinner party at Safra Jurong Grace Assembly of God church A tech - nology company A gym at 12 Kallang Avenue A church in Bukit Timah Mosque in Ang Mo Kio Life Church and Missions Not classified into clus - ters yet Patients diagnosed as Cases 142 and 144 attended the dinner and also visited the Kallang gym and the Bukit Timah church respectively The first patient to belong to a cluster was registered as Case 8
 

While some from the dinner party were declared as confirmed cases early (Cases 94 and 96), there were many who were declared much later (Cases 218 and 224). Some attendees of the dinner party (Cases 142 and 117) were confirmed as cases about 20 and 22 days after February 15 - the day it was organised.

Investigations are ongoing for cases which are not yet classified (the grey circles in the graph). New cases get added to a cluster almost every day.

Three new cases were added to the gym cluster and two more to the Bukit Timah cluster on March 20. So by the time the contact tracing ends, the share of cases from the clusters will exceed 50%

Leaking out of the clusters

Case 142, a 26-year-old male, visited two clusters, the dinner party and the gym. The virus spread from him to three others, Cases 211, 236 and 142, not connected to any clusters. So while only 50% of cases are directly connected to the clusters, there are many who indirectly contracted the virus from those who were part of such clusters.

The diagram plots cases which are linked to one another. Some of them are family members.

Cases outside clusters

image/svg+xml 338 321 186 287 248 430 165 212 289 109 348 240 227 229 318 361 260 256 205 208 235 132 204 351 388 86 82 221 143 178 167 353 204 184 335 311 234 177 221 190 172 291 126 364 225 237 368 294 200 350 303 134 166 242 367 359 251 211 142 219 236 267
 

Not all contacts are mapped to a cluster yet. Cases 311, 335 and 243 are linked but not in a cluster yet.

Also read: Spain’s COVID-19 toll surpasses that of China

Many such clusters similar to Singapore were identified in South Korea too. However, unlike Singapore where the source of such clusters was not known, South Korea was able to point to a female patient who was responsible for its biggest COVID-19 cluster. 

South Korea's patient 31, a 61-year-old woman, despite "warnings from doctors", attended church at least twice and went for a buffet lunch with a friend ignoring the symptoms. The contacts she made at the church led to an exponential rise of COVID-19 cases in the country.

How patient  31 went about her business despite warnings

image/svg+xml The 61-year-old woman was a regular at the Shincheonji church. She attended the Daegu city branch of the church at 7.30 a.m. on February 9
 

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