Understanding R nought | Current events in health and medicine | Heatlh & Medicine | Khan Academy



Dr. Rishi Desai is a pediatric infectious disease physician and former epidemiologist with the Centers for Disease Control and Prevention (CDC).

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30 Comments

  1. Where is the name of “r naught” come from? Is it designed exclusively to measure the spread of disease or it’s a common function can be applied to somewhere else?

  2. After all this laborious explanation and calculation, you STILL HAVE NOT answered the basic question about R-naught: WHAT DOES THE NAUGHT MEAN??? Why is it not simply called "R"?? What does the addition of the subscript "naught" signify? Without that explanation, this entire video is basically incomplete and inadequate.

  3. Quick Question Dr. Desai: It seems that the "time period" really matters when it comes to any calculation of R0. Is that time period well defined? Like the time a person stays infected or something like that.. a fixed number for a given disease? Because an R0 = 2 when the time was measured weekly, is the same as an R0 of 2^(1/7) when time is measured daily. So unless the "period of time" has a strict definition, we cannot talk about an R0 without mentioning what time period we're talking about. Am I correct in my understanding?

  4. Dr Rishi, if you look at any common respiratory virus, it is incredibly obvious that R, if it is to have meaning, must be affected by outdoor temperature. Many studies have shown this – Lidwell J. Hyg., Camb. (1965), 63, 427 was an early and good one. Does it make sense to use a model that doesn't include temperature? And is there any other way to explain seasonality? (I say no!) See eg pic of colds in the Netherlands 1925-26 plotted alongside outdoor temp: ​@t​

  5. For perpetuating you are educated, it's actually "r naught" not "nought". At least your pronunciation is right. Naught meaning zero, nothing, non-existent.

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