Local and community spread not the same thing – Dr Thompson

Dr Jerrol Thompson, an infectious disease specialist, has distinguished between local and community spread amidst speculation about the source of infection of St Vincent and the Grenadines’ (SVG) 13th confirmed case of COVID-19.

This country’s 13th confirmed case was announced on Tuesday, April 21 in a release from the National Emergency Management Organisation (NEMO). The release did not specify that the new case was imported as had been said with all previous cases.

Another release followed closely behind the first, which said that there was no evidence of community transmission relative to the virus in SVG. However, it said that preliminary investigations pointed to “a possible local transmission” as the individual had no known travel history.

And Thompson, while speaking on We FM on Wednesday, April 22, said that there are four classes of COVID-19 cases – no case; sporadic cases, which includes imported cases; clusters or local spread; and community spread.

“We have always known that there are four classes. There is what they consider is the ‘no case’. We went past that well over about a month and a half ago when we had our first case. No country in the world right now — 210 countries — are in a situation where there is no case,” he said.

He added that there are also very few countries with fewer than 15 cases of the virus.

Thompson said that the second class of COVID-19 was the “sporadic cases”. He explained that there were different subcategories of this class, but that it typically covers the imported cases.

“The next category is what they call ‘clusters’… and then there’s the fourth category called ‘community spread’,” he said.

According to Thompson, ‘clusters’ also has subcategories, but another term for cluster is ‘local spread’.

The infectious disease specialist explained that a certain amount of intense investigation and contact tracing is necessary to determine whether a case can be considered a local spread.

“There is a certain amount of information that will be available in terms of where this particular case may have originated, but investigations are still incomplete.

I think it’s on that basis why it’s being said that [it is somewhere] in between those two categories of sporadic cases and a cluster in terms of the local spread,” he said.

He further said that community spread differs because it “talks about several cases of no known contact with imported cases or no known contacts of persons at all who might even be local and persons who are positive”.

“So that the community spread is a kind of a more unknown, mysterious type spread that you don’t know the origins of it and there has to be several cases. It’s on that basis that as this is one case, it’s not considered to be community spread. It will fall into one of the categories under the cluster banner of a local spread if anything,” Thompson said.