Covid-19 : Clusters and Stages Explained

By Yoshitha Perera  

The Covid-19 pandemic has resulted in a major public health emergency in Sri Lanka. What’s next and how cautious should we be? We ask the experts. 

What is a Cluster?

In epidemiology, when a greater than expected number of cases of a disease occur in a group of people living or working in the same area, it is called a disease cluster. A disease cluster is a strangely high incidence of a particular disease or disorder in close proximity, in terms of both time and geography. With the global spread of the COVID-19 virus, there have been over 532,263 positive cases reported worldwide. In Sri Lanka 106 positive cases have been reported thus far. 

Many experts have weighed in on how, where and when these 106 contracted the disease. In such discussions, the ‘term’ cluster is often referred to. Following several large public gatherings within the week of the country’s second Covid-19 patient being identified, much has been said about possible clusters within the country. How many clusters does Sri Lanka have and how worried should we be? We asked Dr. Haritha Aluthge of the Government Medical Officers Association (GMOA). 

Do we have Clusters?

Recently, the GMOA estimated that there were 560 persons infected with COVID-19 who are currently amongst our population. They also noted that such persons possibly had contact with 20,000 others. 

“Sri Lanka is currently experiencing a cluster situation,” Dr. Aluthge said. While highlighting the importance of the social distancing at a time like this, Aluthge noted that three cluster zones have been identified as present. “They are Kalutara, Colombo and Gampaha districts, where were anticipate a high possibility of the virus being spread,” he said. 

“According to a research conducted by Johns Hopkins COVID-19 Resource Center, a single COVID-19 positive patient can spread the virus approximately to another eight persons. With the recent numbers, the period between March 25 and April 7 will be a crucial period for Sri Lankans,” he warned. 

106 COVID-19 positive cases were reported within the country so far. Interestingly 70 out of these cases were not reported from within a quarantine centre, according to Dr. Aluthge.  

“It is certainly possible for these 70 Covid-19 positive cases to spread the virus to 560 others. These 560 others may have had contact with 20,000 others. This is a possible cluster situation which can develop over the next two weeks,” Dr. Haritha Aluthge said.  

The Four Stages of Covid-19

Stage 1

According to the World Health Organization (WHO) there are four main stages of transmission of the COVID-19 virus. The first stage is when there are no cases, which according to Dr. Aluthge Sri Lanka has passed, followed by the identification of the Chinese woman who tested positive for Covid-19 on January 26. “Hers was a sporadic case which can be identified as the second stage of the virus transmission,” Dr. Aluthge said.  

Stage 2

When positive COVID-19 cases which have no links to any cluster or source are identified, they are grouped under the sporadic cases stage. At this stage, only a small number of people are affected, the source of the virus is known and it is therefore easier to perform contact tracing and contain the  of the virus. Accordingly, after Sri Lanka diagnosed its second Covid-19 patient; the 52-year-old Sri Lankan tour guide on March 11, the country passed the second stage as well. 

Stage 3

The third stage is when clusters are identified. It can be recognized in two further stages, the Home Cluster (stage 3A) and Village Clusters (stage 3B). “Currently, Sri Lanka is in the Home Cluster situation (stage 3A) which can gradually be transmitted to form a Village Cluster (stage 3B). We have to take this phase very seriously. It can be assumed that, between the period of March 25 and April 07, if social distancing is not practiced in a proper manner, the numbers will rapidly increase” Dr. Aluthage cautioned.    

Stage 4

The fourth stage is where community transmission occurs and can ultimately lead to the creation of a pandemic situation within a country. Dr. Altuthge highlighted that when a country is increasing its social distancing practice, the number of new cases can be drastically reduced.

According to global research, around 60% of people with COVID-19 show mild or no symptoms and the studies show that people who do not present symptoms can also carry the disease and infect others, Dr. Aluthge said.    “This why, it is important to practice social distancing in a proper manner. Worldwide scientists and medical personnel are calling for urgent measures for the closure of schools and banning public gatherings. This is to stop mild and asymptomatic cases fuelling the pandemic,” he said. 

He said that the upcoming fortnight is a challenge for Sri Lanka to identify these ‘silent carriers’ – in other words people who are infected by the new COVID-19 virus but show delayed or no symptoms. People are more or less unable to identify where they might have picked up the virus from or even if they have been infected with the virus.

What are the experts doing about it?

While explaining the modes which state medical authorities are currently using to identify and control these ‘silent carriers’, Dr. Aluthge said that the main two modes currently in practice are social distancing and contact tracing. “Social distancing is a passive mode while contact tracing can be identified as an attacking mode,” he said. 

Dr. Aluthge said that currently with the help of the tri-forces, the government medical authorities have identified 20,000 houses through contact tracing. He said that the government will continue to monitor these families closely over the next two weeks. 

In the meantime, Dr. Aluthge advised people to cooperate with the efforts of the authorities by adhering to safety measures conducted by the government, as the forthcoming two weeks would be a challenging time. “Remain indoors whether the curfew is temporary lifted or not,” he said.