These files contain data on the 14-day notification rate of newly reported COVID-19 cases per 100 000 population and 14-day notification rate of reported deaths per million population by week and country, in EU/EEA and the UK. Each row contains the corresponding data for a given indicator, week and country. The files are updated weekly.
Why isn't R enough?
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We have all become used to thinking about R, the reproduction ratio (or sometimes called the reproduction number) of a disease. That's the number of people infected, on average, by a single infected person. As we saw in previous articles, R helps us understand what is happening with the disease: R>1 means that the epidemic will grow, R=1 means we are plateauing, R
(Note that the R we hear about on the news each day changes over the course of the epidemic, it is the effective reproduction number rather than the basic reproduction number, R0, that you might also have heard of – you can find out more about the difference between them here.)
The reproduction rate (R) is the average number of secondary infections produced by a single infected person. In England, the Government says the rate of reproduction sits at around 0.8 to 1.0. (of a motion picture) suitable for those under 17 years of age only when accompanied by an adult. Mature, adult, or vulgar: R-rated language; R-rated jokes.
One thing that R does not tell us, though, is how quickly things are changing. This is because R is not a rate, there is no timescale involved. For example, if R=2 for some disease then we know the epidemic will grow (because R>1), but we cannot tell how quickly. For diseases like HIV or TB, where there can be months or years between one person infecting the next person, even R=2 means slow growth over time. However for influenza or measles, where the infection is much faster, on the scale of days, R=2 means very rapid growth.
Here are two example curves for the growth of infection, both with a reproduction ratio R=2. The difference is the time between new infections – several months for HIV but just days for measles.
What is the growth rate of an epidemic?
The growth rate of a disease is a natural way to capture how quickly the number of infections are changing day by day. The growth of cases of a disease is modelled using an exponential curve:
Here is the number of cases, which depends on time measured in days, and (pronounced 'lambda') is what is called the growth rate of the disease per day. (The number is a mathematical constant approximately equal to 2.719 and intimately connected to exponential growth.)For the example curves above, the growth rate for HIV is =0.002 per day and for measles is =0.06 per day. This leads to wildly different outcomes over the next month despite both diseases in this example having the same reproduction ratio. You can use the interactivity below to explore how the progression of a diseases changes for different growth rates (use the slider to change the value of ).
Us R Rate
During the COVID-19 pandemic the number of new cases, and new deaths, is reported each day – we watched in horror as these increased in the UK in March and early April, and have now seen them decrease over recent weeks. If the growth rate is positive, the number of new cases each day is increasing, if the growth rate is 0, the number of new cases stays constant. What is needed to keep the epidemic under control is for the growth rate to be negative and hence the number of new cases to be decreasing. If the number of new cases has decreased by 3% since yesterday, then the growth rate is, approximately, = -0.03 per day. (This isn't exactly equivalent but a good approximation for typical values of . The growth rate actually works like compound interest which you can read about here.)
Which is better: R or the growth rate?
Both the reproduction ratio , and the growth rate, , are valid measures for understanding the growth of a disease. They each have their uses, as outlined below:
| Reproduction ratio: R | Growth rate per day: |
|---|---|
R is more natural for understanding strength of intervention needed to stop an epidemic, better for planning control measures. For example:
| Growth rate is more natural for thinking about how cases change over time. For example
|
| R>1 exponential growth R=1 flat R | >0 exponential growth |
| R a ratio of cases by infection generation. It is not a rate: there is no timescale involved. | The growth rate is a rate, usually given in days for COVID-19. |
| R is not at all easy to measure in practice, but can be fitted using models if the timescales of infection are known. In principle it could be estimated by detailed epidemiological data on exactly who got infection from whom, but this is not usually feasible in typical settings. | The growth rate is relatively easy to estimate from time series data of cases or deaths (but see below about small numbers). A simple approach is just to find the gradient of the logged cases. More advanced approaches, which can take into account a time-varying growth rate, or heterogeneous population, again involve fitting epidemic models. |
Both the reproduction ratio and the growth rate are particularly hard to estimate when the number of cases is small, for example if the incidence of the disease is very low, or if the community you are studying has a very small population. In that case, day to day fluctuations can easily swamp the underlying patterns of the disease, so you will have greater uncertainty about the growth rate (and so expect wider confidence intervals).
How do you get from R to the growth rate and vice versa?
The precise relationship between R and the growth rate is not straightforward: it needs to take into account the timings of each infection to the next. A crude approximation is
where is the mean generation time: the time from one infection to the next.R Rater
I can cope with some advanced maths, tell me more!
OK! All of this supposes that the control measures and number of people susceptible to the disease are not changing too quickly.
Following one infected person, denote their time since infection by (in days). They go on to infect others on average. For each of these, their timing of infection is distributed with probability density function . Then (exercise for maths undergraduates!) and are related as follows:
and yes, this is very closely related to a Laplace transform, or a moment generating function for the generation time distribution.
For specific distributions for the generation time, for example a gamma distribution, this can sometimes be simplified. Taking the generation time to be exactly constant, say , we recover the , but this is a rather crude approximation for many infectious diseases in practice.
Note, depends on a variety of things, including biological things like the incubation period, and on social factors like whether you still mix with others when you have symptoms or if you self-isolate.
See this paper by Wallinga and Lipsitch for more details.
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About this article
Rachel Thomas and Marianne Freiberger are the Editors of Plus. This article was produced with Julia Gog, Professor of Mathematical Biology at the University of Cambridge, as part of our collaboration with JUNIPER, the Joint UNIversity Pandemic and Epidemic Response modelling consortium. JUNIPER comprises academics from the universities of Cambridge, Warwick, Bristol, Exeter, Oxford, Manchester, and Lancaster, who are using a range of mathematical and statistical techniques to address pressing question about the control of COVID-19. You can see more content produced with JUNIPER here.
Gog is also a member of SPI-M, a modelling group which feeds its results into theScientific Advisory Group for Emergencies (SAGE), and of the steering committee of a national consortium, led by the Royal Society, to deal with the COVID-19 pandemic.
Strike rate refers to two different statistics in the sport of cricket. Batting strike rate is a measure of how quickly a batsman achieves the primary goal of batting, namely scoring runs. Bowling strike rate is a measure of how quickly a bowler achieves the primary goal of bowling, namely taking wickets (i.e. getting batsmen out).
Both strike rates are relatively new statistics, having only been invented and considered of importance after the introduction of One Day International cricket in the 1970s.[citation needed]
R Rated Meaning
Batting strike rate[edit]
Batting strike rate (s/r) is defined for a batsman as the average number of runs scored per 100 balls faced. The higher the strike rate, the more effective a batsman is at scoring quickly.
In Test cricket, a batsman's strike rate is of secondary relevance to his ability to score runs without getting out. This means a Test batsman's most important statistic is generally considered to be his batting average, rather than his strike rate.
In limited overs cricket, strike rates are of considerably more importance. Since each team only faces a limited number of balls in an innings, the faster a batsman scores, the more runs his team will be able to accumulate. Strike rates of over 150 are becoming common in Twenty20 cricket.[1] Strike rate is probably considered by most as the key factor in a batsman in one day cricket. Accordingly, the batsmen with the higher strike rate, especially in Twenty20 matches, are more valued than those with a lesser strike rate.
Highest career strike rate (T20I)[edit]
| Strike rate | Runs scored | Balls faced | Batsman | Team | T20I career span |
|---|---|---|---|---|---|
| 165.80 | 577 | 348 | Ravija Sandaruwan | Kuwait | 2019–2020 |
| 158.92 | 1,761 | 1,109 | Glenn Maxwell | Australia | 2012–2021 |
| 158.52 | 558 | 352 | Tim David | Singapore | 2019–2020 |
| 156.44 | 1,724 | 1,102 | Colin Munro | New Zealand | 2012–2020 |
| 155.74 | 989 | 635 | Evin Lewis | West Indies | 2016–2021 |
| Qualification: 250 balls. Last updated: 7 March 2021[2] | |||||
Highest career strike rate (ODI)[edit]
| Strike rate | Runs | Balls faced | Player | Team | Period |
|---|---|---|---|---|---|
| 130.22 | 1,034 | 794 | Andre Russell ‡ | West Indies | 2011–present |
| 124.99 | 3,171 | 2,537 | Glenn Maxwell ‡ | Australia | 2012–present |
| 118.66 | 3,872 | 3,263 | Jos Buttler ‡ | England | 2012–present |
| 117.31 | 1,267 | 1,080 | Hardik Pandya | India | 2016–present |
| 117.06 | 590 | 504 | Lionel Cann | Bermuda | 2006–2009 |
| Qualification: 500 balls faced. Last updated: 28 March 2021[3] | |||||
Bowling strike rate[edit]
Bowling strike rate is defined for a bowler as the average number of balls bowled per wicket taken. The lower the strike rate, the more effective a bowler is at taking wickets quickly.
Although introduced as a statistic complementary to the batting strike rate during the ascension of one-day cricket in the 1980s, bowling strike rates are arguably of more importance in Test cricket than One-day Internationals. This is because the primary goal of a bowler in Test cricket is to take wickets, whereas in a one-day match it is often sufficient to bowl economically - giving away as few runs as possible even if this means taking fewer wickets.
Best career strike rate (ODI and T20I)[edit]
Best career strike rate (Tests)[edit]
| Strike rate | Player | Country | Balls | Wickets |
|---|---|---|---|---|
| 34.1 | George Lohmann | 3830 | 112 | |
| 37.7 | J. J. Ferris | / | 2302 | 61 |
| 38.8 | Shane Bond | 3372 | 87 | |
| 41.7 | Sydney Barnes | 7873 | 189 | |
| 42.3 | Dale Steyn | 18608 | 439 | |
Qualification: 2,000 balls | ||||
| Strike rate | Player | Country | Balls | Wickets |
|---|---|---|---|---|
| 30.0 | Duanne Olivier | 1440 | 48 | |
| 33.3 | Kyle Jamieson | 1202 | 36 | |
| 40.8 | Kuldeep Yadav | 1063 | 26 | |
| 41.7 | Kagiso Rabada | 8431 | 202 | |
| 47.1 | Pat Cummins | 7734 | 164 | |
| 48.5 | Anrich Nortje | 1894 | 39 | |
| 48.9 | James Pattinson | 3963 | 81 | |
| 49.0 | Hasan Ali | 2107 | 43 | |
| 49.0 | Jasprit Bumrah | 4075 | 83 | |
| 49.2 | Lungi Ngidi | 1183 | 24 | |
| 49.3 | Mitchell Starc | 12575 | 255 | |
| 49.9 | Mohammad Shami | 8999 | 180 | |
Qualification: 1,000 balls | ||||
References[edit]
- ^'Records - Twenty20 Internationals - Batting records - Highest career strike rate - ESPN Cricinfo'.
- ^'Records–Twenty20 Internationals–Batting records–Highest career strike rate–ESPN Cricinfo'. Cricinfo. ESPN. Retrieved 2 February 2020.
- ^'Highest strike rate in One Day International cricket'. ESPNcricinfo. Archived from the original on 22 June 2019. Retrieved 24 July 2019.
- ^ ab'Test matches – Bowling records – Best career strike rate'. Cricinfo. ESPN. Retrieved 26 February 2021.
R Ratemypoop