Tuesday 29 September, 2020

What's contact tracing? Dr Avery Hinds explains

The public is being asked to remain at home and self-isolate if possible in order to prevent the spread of the novel coronavirus disease (COVID-19).

As of March 24, 2020, at 4.30 pm, the Ministry of Health confirmed 57 positive cases and urged the public to minimise contact in order to prevent any possible spread of the virus.

Speaking at a media briefing on Tuesday, medical epidemiologist at the Ministry of Health, Dr Avery Hinds explained the terms used within contact tracing and how it is conducted. 

Here’s are some common terms used in contact tracing:

Primary Contact

Primary contacts are the first set of people the patient comes into contact with, usually family members.

If anyone in the household contracts the virus, they would be classed as a primary contact.

Secondary contact

If a primary contact goes to school, work, church, or any other location outside of the home, and the virus is transmitted to someone at those locations, they are referred to as secondary contacts.

For example if a child from the household goes to school and a classmate contracts the virus, they would be classed as a secondary contact.

If a family member goes to church and spreads the disease, those people would also be secondary contacts.

Tertiary contacts

People who interact with secondary contacts and contract the disease are known as tertiary contacts.

Community spread

Community spread occurs where the person testing positive for the disease had no known contact or interaction with a known COVID-19 case, according to PAHO/WHO.

How is contact tracing carried out?

Dr Hinds said contact tracing is carried out initially by reaching out to primary contacts to find out who might have been exposed.

“We identify persons who were potentially exposed and people who were confirmed with COVID-19. We ask those individuals with whom they’ve been in contact.”

“Initial people they would have been in contact with are usually family members who are primary contacts. Those primary contacts are asked to quarantine at home.”

“We then follow up with these persons to find out whether during the course of their exposure, subsequent to the exposure during the course of what we call the incubation period, the 14-day period, whether they developed any symptoms.”

“If they become symptomatic then they’re followed up to get testing and medical management.”

Dr Hinds said the Ministry also reaches out to potential secondary contacts.

“Our medical systems are geared toward making calls to the people with whom a potential case may have been in contact and notifying them that they may have been exposed.”

Dr Hinds said those people are advised to self-isolate at home and monitored to see if symptoms develop.

He said the measure to ask everyone to limit gatherings is one of precaution.

“The reason we’re asking people outside of these gatherings to limit their movement is because although we know not every cough is a COVID-19 case, we are acting on a precautionary principle.”

He said technology is used to create geo-locations of these contacts for analysis to see where they are likely to move around. 

“We map the patients and contacts, we can visualise the change of transmission…and hot spots.”

He said understanding the geographic locations of this data can help them to decide where to allocate resources.

 

Imported versus local transmission

Here’s an explanation of an imported case versus a locally transmitted case by Dr Stephanie Fletcher-Lartey, Consultant, Caribbean Public Health Agency (CARPHA):

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