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Is that true? I'm more worried about false negatives on connections. Two concerns (as a layperson): 1) Transmission via surfaces is thought to be important (af

Is that true? I'm more worried about false negatives on connections. Two concerns (as a layperson): 1) Transmission via surfaces is thought to be important (afaik). You don't have to be in the same place at the same time to transmit. 2) My bluetooth seems pretty slow and unreliable when connecting to my headphones. Is it reliable for logging ~50 proximities during my trip to the supermarket?

zby 7y ago
Ad. 2 - it is not that bad: duration of proximity is correlated with both infection probability and connection probability.
arghwhat 7y ago
1) That would be difficult to solve. If we used position reporting, and considered an area infected for a few days after an infected person arrived, it would most likely lead to unmanageable amounts of false positives. 2) Scanning is mostly just listening and waiting for other devices to send beacons. With one discoverable device nearby, it might take a moment to hear anything. With 50 devices nearby, you scan should be spammed with results. You might have missed a few devices if you were unlucky and moved out of range before they got a successful beacon through. However, in that case you could use second-hand proximity to find the "lost" contact through some of the successful ones.
HSO 7y ago
> 1) Transmission via surfaces is thought to be important (afaik). According to Hendrik Streeck, a leading researcher in Germany, this may not be the case: https://youtu.be/VP7La2bkOMo?t=231 https://youtu.be/VP7La2bkOMo?t=231 They are working on a more formal study of this but indications are that the viruses that other teams have found on surfaces may be "dead" (in the sense that they cannot actually replicate anymore and therefore are not bioactive relatively soon after leaving host organisms). Video only in German, sorry, sure this will get publicized internationally if the study confirms the indications.
- xenonite 7y ago
  as you say it _may_ not be the case. So, as long as no one knows for sure...
  - deleted 7y ago
    [deleted]
- xenonite 7y ago
  This totally contradicts another study [1]. They found that the virus is "viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculum shed)." [1] https://www.nejm.org/doi/10.1056/NEJMc2004973 https://www.nejm.org/doi/10.1056/NEJMc2004973
  - HSO 7y ago
    that's only a letter not a paper. and they only measured the quantity, not whether the viruses they found after x hours could actually still replicate.
    - xenonite 7y ago
      Thank you for the hint (in the reference [1], the measurement done as in [2], which states "Collected aerosols were analysed by quantitative real-time polymerase chain reaction (qRT-PCR) and by virus titration"), although I then don't get why the paper [1] writes that the viruses are "infectious". [1] https://www.nejm.org/doi/10.1056/NEJMc2004973 https://www.nejm.org/doi/10.1056/NEJMc2004973 [2] https://www.eurosurveillance.org/content/10.2807/1560-7917.ES2013.18.38.20590 https://www.eurosurveillance.org/content/10.2807/1560-7917.E...
semi-extrinsic 7y ago
They should do a dead-simple PoC to demonstrate this actually working with Bluetooth. Just make a stupidly simple test app, get 100 volunteers to install the app, have them all wear masks etc. while walking around randomly in the same big room for half an hour. Then see what the false negative rate is - unless the average number of "others seen" is close to 100, this isn't going to work.
- adrianN 7y ago
  I saw a video clip of a test like that, though it didn't contain any results. What makes you think that the developers didn't test it?
  - semi-extrinsic 7y ago
    Because it's an obvious sticking point, everyone's had trouble with bluetooth not recognizing the same ol' headset, the burden of evidence is on the developers. And if they have done the test and not published the results, I'm twice as skeptical.
pas 7y ago
Surfaces can be cleaned easily and should be cleaned frequently. (Eg on public transport.) Furthermore any kind of app will only reach a subset of the population. (Senior citizens are unlikely to install this app.) Yes, bluetooth drivers are a horrible hellscape of cyberspace, but it's probably because connecting to a sink/source (speaker/mic/camera/whatever) sets up the corresponding audio/media/etc channels too, and the interaction of the relevant components (pairing, PIN, kernel modules, gstreamer or who knows what) is what requires a very fragile dance. I have no idea how broken the BLE part is. Firechat doesn't seem that bad and it uses Bluetooth too.

zby 7y ago

Ad. 2 - it is not that bad: duration of proximity is correlated with both infection probability and connection probability.

arghwhat 7y ago

1) That would be difficult to solve. If we used position reporting, and considered an area infected for a few days after an infected person arrived, it would most likely lead to unmanageable amounts of false positives. 2) Scanning is mostly just listening and waiting for other devices to send beacons. With one discoverable device nearby, it might take a moment to hear anything. With 50 devices nearby, you scan should be spammed with results. You might have missed a few devices if you were unlucky and moved out of range before they got a successful beacon through. However, in that case you could use second-hand proximity to find the "lost" contact through some of the successful ones.

HSO 7y ago

> 1) Transmission via surfaces is thought to be important (afaik). According to Hendrik Streeck, a leading researcher in Germany, this may not be the case: https://youtu.be/VP7La2bkOMo?t=231 https://youtu.be/VP7La2bkOMo?t=231 They are working on a more formal study of this but indications are that the viruses that other teams have found on surfaces may be "dead" (in the sense that they cannot actually replicate anymore and therefore are not bioactive relatively soon after leaving host organisms). Video only in German, sorry, sure this will get publicized internationally if the study confirms the indications.

xenonite 7y ago
as you say it _may_ not be the case. So, as long as no one knows for sure...
- deleted 7y ago
  [deleted]
xenonite 7y ago
This totally contradicts another study [1]. They found that the virus is "viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculum shed)." [1] https://www.nejm.org/doi/10.1056/NEJMc2004973 https://www.nejm.org/doi/10.1056/NEJMc2004973
- HSO 7y ago
  that's only a letter not a paper. and they only measured the quantity, not whether the viruses they found after x hours could actually still replicate.
  - xenonite 7y ago
    Thank you for the hint (in the reference [1], the measurement done as in [2], which states "Collected aerosols were analysed by quantitative real-time polymerase chain reaction (qRT-PCR) and by virus titration"), although I then don't get why the paper [1] writes that the viruses are "infectious". [1] https://www.nejm.org/doi/10.1056/NEJMc2004973 https://www.nejm.org/doi/10.1056/NEJMc2004973 [2] https://www.eurosurveillance.org/content/10.2807/1560-7917.ES2013.18.38.20590 https://www.eurosurveillance.org/content/10.2807/1560-7917.E...

semi-extrinsic 7y ago

They should do a dead-simple PoC to demonstrate this actually working with Bluetooth. Just make a stupidly simple test app, get 100 volunteers to install the app, have them all wear masks etc. while walking around randomly in the same big room for half an hour. Then see what the false negative rate is - unless the average number of "others seen" is close to 100, this isn't going to work.

adrianN 7y ago
I saw a video clip of a test like that, though it didn't contain any results. What makes you think that the developers didn't test it?
- semi-extrinsic 7y ago
  Because it's an obvious sticking point, everyone's had trouble with bluetooth not recognizing the same ol' headset, the burden of evidence is on the developers. And if they have done the test and not published the results, I'm twice as skeptical.

pas 7y ago

Surfaces can be cleaned easily and should be cleaned frequently. (Eg on public transport.) Furthermore any kind of app will only reach a subset of the population. (Senior citizens are unlikely to install this app.) Yes, bluetooth drivers are a horrible hellscape of cyberspace, but it's probably because connecting to a sink/source (speaker/mic/camera/whatever) sets up the corresponding audio/media/etc channels too, and the interaction of the relevant components (pairing, PIN, kernel modules, gstreamer or who knows what) is what requires a very fragile dance. I have no idea how broken the BLE part is. Firechat doesn't seem that bad and it uses Bluetooth too.