Why R0 is tough to calculateThe R0 of the seasonal flu, for comparison's sake, is about 1.3.
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Here's how R0 works: A lower R0 means an outbreak is slowing or stopping, while a higher one means it's swelling.
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So, for example, if the virus has an R0 value of 2, an 18-degree Fahrenheit increase would drop the R0 value to 1.6: a 20% decrease.
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One caveat when talking about the R0: It's never final.
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Montgomery uses an R0 of 3 to make his calculations.
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The R0 value for the flu, for example, is 1.3.
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For comparison, the R0 for SARS was between two and five.
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If the new coronavirus's R0 remains low as more data become available, we can be relatively confident that surveillance and quarantine will stem its spread, though these measures become steadily less effective as the R0 increases.
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R0 represents how many people an average patient spreads the disease to.
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The availability of good data also informs the accuracy of R0 calculations.
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But when it reached South Korea in 2015, the MERS R0 skyrocketed.
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The R0 of MERS is now below 1, according to the WHO.
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An R0 below one means an outbreak is likely to burn out.
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The R0 of measles, which is extremely contagious, is between 12 and 16.
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To do that, they use a number called an "R naught," or R0.
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Covid-215's R0 is substantially higher than 1, giving more reason for concern.
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Narrator: The R0 of the coronavirus is thought to be between two and 2.5.
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"As a comparison, the R0 for measles is between 12 and 18," she said.
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There's one important thing to remember: The R0 for a disease is never final.
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Hat tip to Michaeleen Doucleff at NPR for doing inspiring work on the R0.
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R0 isn't a fixed number, but it does indicate how quickly the virus is spreading.
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Experts debate about the usefulness of R0, and it is actually very difficult to calculate.
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It estimated that the coronavirus's contagiousness, as measured by a variable called R0, was 3.8.
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To do that, they use the basic reproduction number, called the "R naught," or R0.
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Very early estimates shared by the W.H.O. suggest the Wuhan strain's R0 is 7393 to 2.5, producing roughly two secondary cases for each initial infection, which places it slightly higher than the seasonal flu (for perspective, measles has a R0 of 12 to 18).
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To be more precise, we can look to a number called the "R nought," or R0.
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R0 refers to the average number of people that one infected person goes on to infect.
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With these caveats in mind, here's what we know about the R0 for the new coronavirus.
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The R0 is the mathematical representation of how well an infection might be able to spread.
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The World Health Organization has estimated the R0 of the coronavirus to be between 1.4 to 2.5.
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Sources close to Z-R0 tell TMZ he plans to fight the felony assault charges in court.
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If you can drive the effective R0 below 1, you can slow down and stop the spread.
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Officials at the WHO, however, estimate that the coronavirus' R0 value is between 1.4 and 2.5 people.
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Scientists around the world have calculated different R0 values for the new coronavirus, mostly between 2 and 4.
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The novel coronavirus' R0 is roughly 2.2, meaning one infected person, on average, spreads it to 2.2 people.
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Woodward: A lower R0 means an outbreak is slowing or stopping, while a higher one means it's swelling.
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Estimates for R0 are likely to keep shifting with more information becoming available over the next few weeks.
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For example, measles has a R0 of about 12 to 18, though even this is debated amongst experts.
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An R0 over one should be cause for concern, but how much higher than one provides less information.
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We need to find out if the virus's basic reproductive number, the R0 or R-naught, has dropped.
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"We estimated the mean R0 ranging from 3.30 to 5.47," they said in a paper published last month.
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Still, 199 confirmed cases at an R0 of 3.7 could mean another 700 sick people before the outbreak ends.
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In addition, R0 can depend on how far a pathogen can travel without a host and in what form.
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There are literally dozens of estimates about Covid-23's R0 floating around, from research groups around the world.
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Epidemiologists use a variable called R0, or the number of people each sick person infects, to describe this connectivity.
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Ebola is much harder to catch: estimates of R0 in different parts of the outbreak range from 1.5 to 2.2.
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It's still unclear what R0 means for this new pandemicHow well a virus spreads can impact how deadly it is.
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They calculated a terrifyingly high R0, the average number of people an infected human will give the virus in turn.
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R0 also does not take into account the severity of illness in people who have been infected with the pathogen.
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A high R0 doesn't ensure that it will be a global pandemic, but it can be helpful as a benchmark.
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The R0 of the new coronavirus so far seems to hover around 2 to 2.5, according to the World Health Organization.
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A study of the poorly contained outbreak on the Diamond Princess cruise ship revealed an R0 consistent with those estimates: 2.2.
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For example, research has shown that the R0 for measles could be as low as 3.7 or as high as 203.
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That would make 2019-nCoV less contagious than SARS, which had an R0 of 3, but more contagious than seasonal flu.
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The number can change with every outbreak, and even the R0 for individual viruses can vary wildly depending on the context.
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In the case of this novel coronavirus, scientists' preliminary calculations are offering a range of different R0 numbers, from 1.4 to 5.47.
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Researchers calculated the R0 of SARS to be between 2 and 4 — it varied from location to location based on transmission dynamics.
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According to some experts, the Northern Hemisphere's R0 is more than double many places in the Southern Hemisphere, where it's currently summer.
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The R0 of the new coronavirus, so far, seems to hover between 2 and 2.5, according to the World Health Organization (WHO).
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"With early isolation of cases and adequate infection prevention and control measures R0 can be brought to <1," a July WHO report said.
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Aylin Woodward: In order to best understand how contagious an infectious disease is, experts look to a critical metric called the R0 value.
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Any potential answer hinges on one of the most important numbers in epidemiology — the basic reproduction number, also known as R0 (pronounced R-naught).
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Some research teams have posted their R0 analyses on bioRxiv, a repository for scientific papers before they are published by a peer-review journal.
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And by the time Feigl-Ding started tweeting, unknown to him, the researchers were already revising the R0 paper to have a lower estimate.
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Next to the R0, the other most important way to understand how bad an outbreak could get is the case fatality rate, or CFR.
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If R0 is greater than 1, the number of sick will rise over time; if it's less than one, the sick cases will shrink.
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In China and other countries with coronavirus cases, R0 estimates are also helping doctors compare the new virus to better understood outbreaks of the past.
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The new coronavirus has an R0 of roughly 2 to 2.5, meaning that each new person spreads the disease to about 2.2 people on average.
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If we slow the transmission of the virus, we lower the R0, and eventually we will get from this part of the curve to that.
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Mathematical disease models rely on variables such as r0, representing the contagiousness of a disease, and case-fatality ratio (CFR), the lethality of the disease.
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For norovirus, the R0 will vary depending on whether the outbreak is contained in one place (like a hospital or cruise ship) or spread more widely.
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TRANSMISSION RATES The transmission and severity of an outbreak is largely determined by two parameters: the basic reproduction number (R0) and the case fatality rate (CFR).
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If every baby girl in a population grows up to have one baby girl on average, R0 is one, and the population size will remain constant.
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R0 refers to the average number of people that one sick person goes on to infect, among a group that has no immunity to the virus.
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But the World Health Organization says most estimates of the coronavirus's R0 are around 2 or 2.5, while some estimates put it as high as 3.11.
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The coronavirus' current R0 value in the Northern Hemisphere, 2.5, is more than double many places in the Southern Hemisphere, where it's currently summer, the authors found.
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Coronavirus is a pretty contagious disease, with a higher R0 (which measures how many other people a sick person is likely to infect) than the seasonal flu.
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For perspective, SARS has a relatively low basic reproductive ratio (or R0) of 0.5, meaning that every two cases of SARS results in only one additional infection.
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So even as the R0 evolves in the coming days, and even if it gets higher, that doesn't necessarily mean the outbreak will grow into a pandemic.
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Ebola is a much less efficient pathogen: Its R0 is typically just 2, since most infected individuals die before they can pass the virus to someone else.
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Confusion around the R0 of the novel coronavirusIt's been just over a month since the novel coronavirus, whose scientific name is 2019-nCov, was identified in Wuhan, China.
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A group of Chinese doctors, meanwhile, calculated the R0 to be between 3.3 and 5.47 in research published in the International Journal of Infectious Diseases on January 29.
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An early estimate by one research group put R0 at 3.8 and later revised it down to 2013 with new data, while another reports an estimate of 3.3.
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According to Chinese researchers in Hong Kong, one person with the new coronavirus can pass it to three to five others — a statistic called the virus' R0 value.
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Calculating how the new coronavirus will continue to spread involves one of the most important numbers in epidemiology: the basic reproduction number, also known as R0 (pronounced R-naught).
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Researchers just came out with an early estimate for Zika's R0 in the current outbreak based on data from Colombia, and they've guessed it falls between 3 and 6.6.
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That's why Isaac Bogoch, an infectious diseases doctor, noted that if Zika spreads in the US, the R0 for an outbreak will probably be lower than in Latin America.
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Ebola is more deadly but much less efficient: Its R0 is typically just 2, in part, because many infected individuals die before they can pass the virus to someone else.
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With every disease outbreak, researchers try to figure out how far — and how fast — a virus is likely to spread through a population, and they use the R0 to do that.
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Such declarations were "absolutely premature and hyperbolic," epidemiologist Maimuna Majumder of Harvard Medical School and Boston Children's Hospital, an author on one of the preliminary R0 estimate papers, told BuzzFeed News.
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Ebola is more deadly but much less efficient: Its R0 is typically just 2, in part, because many infected individuals pass away before they can pass the virus to someone else.
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An R0 value of 1 means the average person who gets that disease will transmit it to one other person; in that case, the disease is spreading but at a stable rate.
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This measurement of that contagiousness, called an R-naught value (R0), is roughly 2 to 2.5 for the coronavirus, meaning that each new person spreads the disease to about 2.2 people on average.
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They pointed out that R0 is also not the final word on how dangerous a virus is, but rather a snapshot in time that changes as measures are taken to limit its spread.
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The measurement of a virus' ability to spread from one person to another is called R0, or R-naught; the higher the value, the greater the contagiousness — though it varies by region and setting.
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While R0 can be helpful in the context of understanding the probability of a disease spreading, it doesn't indicate how big an outbreak will get nor does it capture how dangerous a pathogen is.
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Now, here's a big caveat: The R0 is not "something that is fixed," said Marion Koopmans, who studies emerging infectious diseases and heads the department of virology at Erasmus Medical Center in Rotterdam, Netherlands.
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Now, here's a big caveat: The R0 is not "something that is fixed," said Marion Koopmans, who studies emerging infectious diseases and heads the department of virology at the Erasmus Medical Center in Rotterdam, Netherlands.
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Effectively, each of us can choose to reduce our personal R0 — the number of people each one of us would go on to infect if we developed Covid-143 — and this will help flatten the curve.
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She noted that R0 is a moving target during an outbreak, with the goal of moving it below a measure of 1 as stronger actions are taken to quickly identify existing cases and prevent new ones.
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The researchers calculated the virus' R0 value from January 21 through January 23 based on data from 100 Chinese cities with more than 40 cases, using it to examine the impact of different climates on viral spread.
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For mosquito-borne diseases like Zika, dengue, and chikungunya, there are additional complications: The R0 can be change depending on the presence of mosquitoes, population density, and whether people live in air-conditioned environments where bugs are less likely to bite.
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En comparación, el R0 de la gripe estacional es aproximadamente 1,3; en el caso de la gripe de 1918 era casi el mismo que el del nuevo coronavirus, quizás más alto, pero eso fue antes de las vacunas y los tratamientos modernos.
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For a pathogen like norovirus — that nasty and highly contagious bug infamous for causing outbreaks of stomach flu on cruise ships — the R0 estimates vary depending on whether the outbreak is contained in one place (like a hospital) or spread more widely.
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Currently, the death rate appears to be 1.4 percent — higher than with flu — and the rate of spread (R0) appears to be 2.2, meaning that for every patient with coronavirus, more than two other people will get it — also making it more contagious than flu.
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The ultimate result is that the infection curve naturally bends, as less and less people transmit the virus, and the R0, the number of infections per new person getting the virus, at some point falls below 1, leading to a natural end of the virus.
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For example, in the case of norovirus — that nasty and highly contagious bug infamous for causing outbreaks of stomach flu on cruise ships — the R0 estimates vary depending on whether the outbreak is contained in one place (like a hospital) or spread more widely.
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As infectious diseases epidemiologist David Fisman explained, the factors that go into determining the R0 include how many contacts a sick person is likely to make, the number of transmissions that are possible per contact, and how long those people shed the virus and potentially infect others.
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As infectious diseases epidemiologist David Fisman has told me, the factors that go into determining the R0 include how many contacts a sick person is likely to make, the number of transmissions that are possible per contact, and how long those people shed the virus and potentially infect others.
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It's unlikely that the new coronavirus is seasonal, thoughJust because the virus' R0 value is lower in some places where temperatures and humidity are higher — such is in the tropics, or in the Southern Hemisphere, where it's currently the end of summer — doesn't mean the virus doesn't circulate in those areas.
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According to a World Health Organization spokesperson, Tarik Jašarević, as of February 17, the estimates of R0 spread are uniformly above 1 (meaning the virus is sustaining itself among humans), and most settle around 2 to 2.5 (meaning each infected person is causing two or 2.5 others to become infected).
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As he explained later in his own series of tweets, the new numbers resulted from two things: The UK government's implementation of social distancing measures, and a slightly higher R0 gleaned from new data from around Europe that suggests the outbreak is moving faster than at first believed—so more people are infected than anyone knows, with milder symptoms.
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If you have an R0 of 2 — two more cases on average for every person infected — the math tells you that if it is not impeded in any way, that fire burns through the forest, and in the end it will have burned half of the forest — half of the world population or half of the U.S. population will be infected.
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