The latest Sivagangga cluster from Kedah was suspected of being caused by a super spreader strain of the COVID-19 virus that originated from Egypt and Pakistan. Health authorities believed there is a high probability that the cluster is a super spreader because of its higher transmission rate compared to previous COVID-19 clusters. We spoke to Associate Prof. Dr Chan Yoke Fun, Virologist & Senior Lecturer at the Department of Medical Microbiology, Faculty of Medicine, University of Malaya to learn more about super spreaders.
What is a super spreader?
A “super spreader” is a person who has a disproportionately higher ability to infect others with a virus. In COVID-19, it is associated with both explosive growth at the early outbreak and sustained transmission in later stages. Read more here.
How does a person become a super spreader?
Besides the virus, environmental factors can also facilitate super spreading event. For instance, poorly ventilated indoor and confined areas seem especially conducive to the virus’s spread. We have seen that in large outbreak clusters such as nursing homes, churches, food-processing plants, schools, shopping areas, worker dormitories, prisons and ships.
We have heard about superspreader event, for example, a choir practice in Washington infected about 52 people; a megachurch in Seoul was linked to the majority of initial infections in South Korea, and a wedding in Jordan with about 350 guests led to 76 confirmed infections.
Similarly, behavioural factors such as cough hygiene, social customs, health-seeking behaviour, and adherence to public health guidance can amplify a super spreader event.
What’s the impact of super spreaders on COVID-19?
We need to find the super spreader quickly to contain the outbreak.
Have there been other super-spreaders cases in Malaysia?
Currently, the Sivagangga cluster with 45 cases is believed to be caused by super spreader strain. The index case spread to 8 people and it has reached generation 3 of infection.
There are many cluster cases in Malaysia, but not sure if super spreaders are implicated:
- Tabligh with 1037 index case infected 1,143
- Good News Fellowship Conference cluster hosted by a church in Kuching, Sarawak on Feb 26 to 28, 1st generation infected 22 people
- Case 26 infected 25 people
- RK Family Cluster / Italy Cluster- 2 from 2nd generation infected 25
How to contain super spreaders?
Identify them early, implement isolation and provide targeted intervention. Avoid the “three Cs” of transmission: closed spaces with poor ventilation, crowded settings, and close contact with others. It is important to use genomics tracking to identify superspreader. The use of genomic data is important to rapidly identify possible transmission chains and provide a framework in the response to COVID-19.
The Sivangangga index case came back from Tamil Nadu, India. My analysis of the 36 complete genomes from Tamil Nadu showed the circulation of 55.6% of B6 lineage (similar to Malaysia), 42% of B1.1 lineage and one virus with B1.36 lineage. Both B1.1 and B1.36 are known to carry the D614G spike mutation. Once IMR had sequenced the index case and selected cases from different generations, we will be able to identify the mutations these viruses carried. So far, D614G mutation has been shown to have increase infectivity, but has yet to be associated with superspreader.
(Zhang L, Jackson CB, Mou H, et al. The D614G mutation in the SARS-CoV-2 spike protein reduces S1 shedding and increases infectivity. BioRxiv. 2020;doi:10.1101/2020.06.12.148726)
* Update: The Health Ministry is still waiting for the lab results to see if the Sivagangga cluster is linked to the D614G mutated strain.
Associate Prof. Dr Chan Yoke Fun is a virologist currently leading the team at University Malaya in conducting the genome sequencing on the SARS-CoV-2 strain in Malaysia. She has since published 2 genome papers and completed more than 60 SARS-CoV-2 sequences from Malaysia.
**All previous posts about COVID-19 here: https://sciencemediacentremalaysia.com/tag/covid-19/