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The R(0) number

  • 10-05-2020 5:21pm
    #1
    Registered Users Posts: 2,317 ✭✭✭ amandstu


    According to this story it is going up again in Germany (1.1)
    https://www.bbc.com/news/world-europe-52604676

    How do they know this?Can they track that number in (roughly) real time?

    What delay is they in reporting this figure,I wonder?


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Comments

  • Registered Users Posts: 3,863 ✭✭✭ mikhail


    amandstu wrote: »
    How do they know this?Can they track that number in (roughly) real time?

    What delay is they in reporting this figure,I wonder?
    They fit a curve to the recent daily positive tests. For example, if the last ten* days had show exactly the same number of cases each day, the model would show R = 1.

    *I am plucking that number of days from thin air. I don't know how many days' data they use. If you use more days, you get a more precise fit, but if you use fewer days you get a more responsive fit. It's a trade off.


  • Registered Users Posts: 2,317 ✭✭✭ amandstu


    mikhail wrote: »
    They fit a curve to the recent daily positive tests. For example, if the last ten* days had show exactly the same number of cases each day, the model would show R = 1.

    *I am plucking that number of days from thin air. I don't know how many days' data they use. If you use more days, you get a more precise fit, but if you use fewer days you get a more responsive fit. It's a trade off.

    I was just aurprised at how quickly they seemed to notice an uptick in the nunber .It seems like only a coupke of days since restrictions were eased in Germany.

    Maybe,as you say they are using just a few days and so that number may need to be treated with caution for now
    ..


  • Registered Users Posts: 8,304 ✭✭✭ downcow


    I am more and more convinced that the R(0) number is next to nonsense.

    I have tried to research how it is worked out and there seems to be nothing out there to tell us. The best I can find is that Scotland has a 'big computer' that does it.
    It seems it's quite related to deaths and therefore must be three weeks old.

    Can anyone shed some light on how this number is worked out. All the major news media have tried including the BBC and they just simply waffle


  • Registered Users Posts: 2,404 ✭✭✭ DebDynamite


    Can someone please tell me, does the R number mean the amount of people each person (healthy, with no virus) is coming into contact with on avenge, or does it only refer to the amount of person to person transmission of the virus?

    For example, say we were only getting about 5 cases per day, so people were out socialising more and we were back to what we were like in early March, could the R rate be at 4 or 5, but infections still stay low. Is the R rate irrelevant if cases are low, and staying low?


  • Registered Users Posts: 21,702 ✭✭✭✭ mickdw


    Surely they just look at models that take into account distancing etc and see how the cases rise day on day and allow for a percentage undetected cases alzo w8lithin the model. It should tie in also with what they see from contact tracing.
    As far as i know R 0 is a constant which refers to transmission rate within a community that are not resistant and not acting to prevent spread. They should be using another term for the reducing reproductive rate.


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  • Registered Users Posts: 8,304 ✭✭✭ downcow


    mickdw wrote: »
    Surely they just look at models that take into account distancing etc and see how the cases rise day on day and allow for a percentage undetected cases alzo w8lithin the model. It should tie in also with what they see from contact tracing.
    As far as i know R 0 is a constant which refers to transmission rate within a community that are not resistant and not acting to prevent spread. They should be using another term for the reducing reproductive rate.

    Surely if the figure has credibility there is a clear calculation that shows us how it is worked out. What you are saying is basically what the BBC are saying which doesn't really mean anything to me


  • Registered Users Posts: 2,004 ✭✭✭ Hmmzis


    Ro is the default rate of spread between infected and naïve hosts if no behaviour adjustments are made.

    Re is the effective rate of spread for same, but takes into account the actual situation where coutermeasures have been applied.

    Then there is also the K number, that describes the uniformity of the spreading patterns. For the flu and most other respiratory viruses the K is high, for SARS like viruses it's very low (they seem to rely on super spreading events/conditions).

    https://www.sciencemag.org/news/2020/05/why-do-some-covid-19-patients-infect-many-others-whereas-most-don-t-spread-virus-all


  • Registered Users Posts: 21,702 ✭✭✭✭ mickdw


    Hmmzis wrote: »
    Ro is the default rate of spread between infected and naïve hosts if no behaviour adjustments are made.

    Re is the effective rate of spread for same, but takes into account the actual situation where coutermeasures have been applied.

    Then there is also the K number, that describes the uniformity of the spreading patterns. For the flu and most other respiratory viruses the K is high, for SARS like viruses it's very low (they seem to rely on super spreading events/conditions).

    https://www.sciencemag.org/news/2020/05/why-do-some-covid-19-patients-infect-many-others-whereas-most-don-t-spread-virus-all
    But they all keep referring to Ro and it reducing which is wrong.


  • Registered Users Posts: 8,304 ✭✭✭ downcow


    Hmmzis wrote: »
    Ro is the default rate of spread between infected and naïve hosts if no behaviour adjustments are made.

    Re is the effective rate of spread for same, but takes into account the actual situation where coutermeasures have been applied.

    Then there is also the K number, that describes the uniformity of the spreading patterns. For the flu and most other respiratory viruses the K is high, for SARS like viruses it's very low (they seem to rely on super spreading events/conditions).

    https://www.sciencemag.org/news/2020/05/why-do-some-covid-19-patients-infect-many-others-whereas-most-don-t-spread-virus-all

    Thanks for that. A really interesting read.
    Still zero on how R number is established


  • Moderators, Category Moderators, Music Moderators, Politics Moderators, Society & Culture Moderators Posts: 22,298 CMod ✭✭✭✭ Dravokivich


    I thought it was a reproductive rate per case?


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  • Registered Users Posts: 9,465 ✭✭✭ YFlyer


    I'm sure they use calculus. The 2nd derivative.


  • Registered Users Posts: 2,317 ✭✭✭ amandstu


    I thought it was a reproductive rate per case?


    That's right.

    The methodology of giving it a value may be intricate (for all I know) -and dynamic .But I doubt it is rocket science.

    It seems many countries are attaching great importance to it.


  • Registered Users Posts: 9,465 ✭✭✭ YFlyer


    Anyone know what was the highest R0 calculated? This can determine the percentage of population needed to be immune for herd protection.


  • Closed Accounts Posts: 3,748 ✭✭✭ ExMachina1000


    YFlyer wrote: »
    Anyone know what was the highest R0 calculated? This can determine the percentage of population needed to be immune for herd protection.

    I thought we were all laughing at boris Johnson for his thoughts on herd immunity? Its a thing now?


  • Registered Users Posts: 9,465 ✭✭✭ YFlyer


    I thought we were all laughing at boris Johnson for his thoughts on herd immunity? Its a thing now?

    I'm thinking in regard to vaccine.

    R0 predicts the extent of immunization that a population requires if herd immunity is to be achieved, the spread of the infection limited, and the population protected against future infection. To prevent sustained spread of the infection the proportion of the population that has to be immunized (Pi) has to be greater than 1 − 1/R0.

    For example, if R0 = 2, immunization needs to be achieved in 50% of the population. However, if R0 = 5 the proportion rises steeply, to 80%. Beyond that the rise is less steep; an increase in R0 to 10 increases the need for immunization to 90%. Measles has an R0 greater than 10, which is why immunization of a large proportion of the population is so important in preventing the disease.


  • Registered Users Posts: 2,317 ✭✭✭ amandstu


    YFlyer wrote: »
    Anyone know what was the highest R0 calculated? This can determine the percentage of population needed to be immune for herd protection.

    Don't know that (or of that relationship) but 60% is frequently mentioned.
    This seems unattainable in any convenient timeframe.

    There was a story today that the virus may have become less virulent in Italy but the story is behind an adblocker barrier so I can't read it.

    https://www.dailymail.co.uk/news/article-8376105/Is-Covid-19-really-potent.html


  • Registered Users Posts: 2,317 ✭✭✭ amandstu


    YFlyer wrote: »
    I'm thinking in regard to vaccine.

    Heard that around 50% won't even take the vaccine if available (of course herd immunity is "a thing" ..facts of life and all that)


  • Registered Users Posts: 9,465 ✭✭✭ YFlyer


    amandstu wrote: »
    Heard that around 50% won't even take the vaccine if available (of course herd immunity is "a thing" ..facts of life and all that)

    I doubt up to 50% won't take the vaccine. Anyway if true an R0 of 2 or less would handle those numbers.


  • Registered Users Posts: 9,465 ✭✭✭ YFlyer


    amandstu wrote: »
    Don't know that (or of that relationship) but 60% is frequently mentioned.
    This seems unattainable in any convenient timeframe.

    There was a story today that the virus may have become less virulent in Ital but the story is behind an adblocker barrier so I can't read it.

    https://www.dailymail.co.uk/news/article-8376105/Is-Covid-19-really-potent.html

    That would give an R0 of over 2.


  • Registered Users Posts: 2,317 ✭✭✭ amandstu


    YFlyer wrote: »
    I doubt up to 50% won't take the vaccine. Anyway if true an R0 of 2 or less would handle those numbers.


    How so ? R(0)=2 means fast exponential growth


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  • Registered Users Posts: 2,317 ✭✭✭ amandstu


    Are we getting confused between a "natural"R(0)number and a mitigated one?


  • Registered Users Posts: 9,465 ✭✭✭ YFlyer


    amandstu wrote: »
    How so ? R(0)=2 means fast exponential growth

    I'm reference from here

    https://www.cebm.net/covid-19/when-will-it-be-over-an-introduction-to-viral-reproduction-numbers-r0-and-re/


  • Registered Users Posts: 9,465 ✭✭✭ YFlyer


    amandstu wrote: »
    Are we getting confused between a "natural"R(0)number and a mitigated one?

    Values now in each region or country looks like they're the different mitigated R0 number.

    For population or herd immunity the natural R0 would be required.


  • Registered Users Posts: 2,317 ✭✭✭ amandstu


    YFlyer wrote: »
    I doubt up to 50% won't take the vaccine. Anyway if true an R0 of 2 or less would handle those numbers.


    Thanks for the article .I get you now. Yes the R(0) and the R(e) numbers seem to be misused on the TV these days.

    Ideally the R(0) number never changes but it is spoken of as changing from week to week , where it should really be referred to as the R(e) or the R(t)
    number

    Yes ,if the public will not take the vaccine in large enough numbers then those already having had the illness will count as "already vaccinated" and so boost the numbers.


  • Registered Users Posts: 9,465 ✭✭✭ YFlyer


    Yes ,if the public will not take the vaccine in large enough numbers then those already having had the illness will count as "already vaccinated" and so boost the numbers.[/quote]

    Unfortunately those percentages will unlikely protect the population as you could have significant size clusters that would either vaccinate or not vaccinate.


  • Registered Users Posts: 8,304 ✭✭✭ downcow


    Am I assuming you are all in same position as me ie no clue where this mysterious daily changing r number comes from or how it is calculated?


  • Closed Accounts Posts: 9,586 ✭✭✭ Roselyn Nutritious Dwarf


    Would it be safe to assume the R number might increase for Dublin next week, after 1,000+ covidiots today spent more than 15mins together, in close proximity, on a walkabout with a majority not even wearing facemasks properly?


  • Registered Users Posts: 3,216 ✭✭✭ Polar101


    downcow wrote: »
    Am I assuming you are all in same position as me ie no clue where this mysterious daily changing r number comes from or how it is calculated?

    In Germany it's the number of cases today compared to what is was 4 days earlier.

    I read it on page 6 of this publication:

    https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/2020-05-10-en.pdf?__blob=publicationFile

    Happy to be corrected/re-educated, as I'm not mathematically gifted. Assuming other countries use similar methods.


  • Registered Users Posts: 8,304 ✭✭✭ downcow


    Polar101 wrote: »
    In Germany it's the number of cases today compared to what is was 4 days earlier.

    I read it on page 6 of this publication:

    https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/2020-05-10-en.pdf?__blob=publicationFile

    Happy to be corrected/re-educated, as I'm not mathematically gifted. Assuming other countries use similar methods.

    Great article.

    It appears it the number is quite old ie based on displayed symptoms (6-14 days after infection) and in addition the last 3 days are disregarded, so it takes no account of last 9 days and is only to be trusted 17 days later.
    Big brother doesn’t tell us this. The number should also surely be modified every day for 17 days - they are not telling us this either.
    Clearly we are being treated like mushrooms. But i wonder how has the info. Does government even know.


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  • Registered Users Posts: 2,004 ✭✭✭ Hmmzis


    Would it be safe to assume the R number might increase for Dublin next week, after 1,000+ covidiots today spent more than 15mins together, in close proximity, on a walkabout with a majority not even wearing facemasks properly?

    Unfortunately, anything else would be nothing short of miraculous.


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