Since its launch, the CoronaMelder app has been downloaded by 3.7 million people in the Netherlands. Approximately 10,000 people per day are being notified of exposure. Of this number, a small percentage were more than 1.5 meters away from the infected person.
This is all according to the Chief Information Officer at the Ministry of Health, Ron Roozendaal. He admits to the NOS that “In the vast majority of cases, the app recognizes the distance correctly. But in a small number of cases you were further away.”
It is estimated that about 70% of people who receive a report from the App were within 1.5 meters of the infected person for more than 15 minutes, meaning the app is accurate in the majority of cases.
However, about 20% of people who receive a notification may have actually been a safe distance away from the infected person.
During the testing of the app, 80 subjects were told to stand at a great distance (between three and ten meters) from the “infected” person. It was found that a handful of these subjects still received a notification.
Dozens of people a day
Roozendaal explains that if we are to apply this margin of error to the everyday use of the app, a small amount of people who receive a notification were actually within a safe distance from an infected person, “out of 10,000 reports per day, there are still dozens.”
However, in all cases where someone is notified, they were in proximity to the infected person for at least 15 minutes.
Maximum 10 meters
The CoronaMelder app works via bluetooth. This means that those who do receive an incorrect notification were at least 10 meters from another infected person. However, Roozendaal explains that the chance of a notification being sent if someone is 10 meters away is extremely small.
The app measures the strength of a nearby bluetooth signal and then estimates how close a person was to another app user. Meaning that where you place your phone — in your pocket or on the table, for example — is going to affect the estimate.
“If you have two telephones on a table 2.5 meters apart, and one of the two is from someone who has tested positive and also uses the corona app, you could well receive a notification. If you have it in your pocket, the chance is much smaller,” Roozendaal explains.
He has emphasised that in most cases, the app is accurate and a person has been exposed. Even if the app picked up on someone who was a little over 1.5 meter distance, you have been close, he says. “At least fifteen minutes and in any case close by. So that’s why the advice applies: if you have received a report, go to quarantine.”
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Feature Image: Canva/DutchReview