A graph from Johns Hopkins University is being circulated on Facebook with the claim that the USA has attained herd immunity. At the time of writing this article, the graph was shared over 3,000 times. According to the caption of the viral post, a declining positivity rate for COVID-19 tests indicates that the US has reached herd immunity.
"Ask any biostatistician what it means when you test hundreds of thousands of people a day for infectious disease and return a consistently lowering the positivity rate. I'll give you a clue: it means heard immunity has been reached and the virus is dying out," reads a part of the caption.
What Is Herd Immunity?
Herd immunity, or community immunity, is attained when a considerable part of the population of an area is immune to a specific disease.
The USA has attained Herd-Immunity.
The claim is false.
According to Dr Jennifer Nuzzo, the lead epidemiologist on the team that made the graph at Johns Hopkins, people are misinterpreting the graph as showing how easily the virus is spreading.
"You can't say this is a measure of the amount of infection that's occurring in the community," AP quoted Nuzzo as saying. "It is a measure of if you are doing enough testing," she added.
The team involved in creating the graph informed that the number of positive tests as a percentage of total tests is indicative of whether a higher rate of testing is required. It also shows which members of the population are being tested.
Inferences From Graph
Reportedly, a high positivity rate suggests that a community might be testing mostly the sickest patients, and could be missing milder or asymptomatic cases.
A lower positivity rate may indicate a community is also testing patients with milder or no symptoms.
According to Jaquelin Dudley, a professor of molecular biosciences at the University of Texas at Austin, it is possible that there are areas where herd immunity has been established, however, "there are still many unknowns, including lack of testing for asymptomatic individuals or missing the right point during infection for testing."
She added that at the moment, a timeline for when there will be herd immunity throughout the United States can't be accurately predicted.
Experts have opined that 70% of the USA population which is more than 200 million people, would have to recover from COVID-19 to hinder the spread of the epidemic.
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