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103-406: The tournament uses a unique format not seen in other ATP Tour events, where the singles players and doubles teams are separated into two groups of four, within which they each play three round-robin matches. After the round-robin stage, the top two performers from each group play in knock-out semifinals and a final to determine the champion(s). The tournament was first held in 1970, shortly after

206-463: A bye . The schedule can therefore be computed as though the dummy were an ordinary player, either fixed or rotating. Instead of rotating one position, any number relatively prime to ( n − 1 ) {\displaystyle (n-1)} will generate a complete schedule. The upper and lower rows can indicate home/away in sports, white/black in chess , etc.; to ensure fairness, this must alternate between rounds since competitor 1

309-625: A healthy diet are also recommended. Supportive care in severe cases includes treatment to relieve symptoms , fluid therapy , oxygen support and prone positioning , and medications or devices to support other affected vital organs. More severe cases may need treatment in hospital. In those with low oxygen levels, use of the glucocorticoid dexamethasone is recommended to reduce mortality. Noninvasive ventilation and, ultimately, admission to an intensive care unit for mechanical ventilation may be required to support breathing. Extracorporeal membrane oxygenation (ECMO) has been used to address

412-615: A variant of concern (VoC) or a variant of interest (VoI). Many of these variants have shared the more infectious D614G . As of May 2023, the WHO had downgraded all variants of concern to previously circulating as these were no longer detected in new infections. Sub-lineages of the Omicron variant (BA.1 – BA.5) were considered separate VoCs by the WHO until they were downgraded in March 2023 as no longer widely circulating. As of 24 September 2024 ,

515-464: A bye. If the number is even, an added player (ω) becomes the opponent. For an even number n {\displaystyle n} or an odd number n − 1 {\displaystyle n-1} of competitors, Schurig builds a table with n / 2 {\displaystyle n/2} vertical rows and n − 1 {\displaystyle n-1} horizontal rows. Then he populates it starting from

618-485: A certain number of wins or losses. The term round-robin is derived from the French term ruban ('ribbon'). Over time, the term became idiomized to robin . In a single round-robin schedule, each participant plays every other participant once. If each participant plays all others twice, this is frequently called a double round-robin . The term is rarely used when all participants play one another more than twice, and

721-411: A competitor to play the strongest opponents in a round robin in quick succession while others play them intermittently with weaker opposition. This asymmetry means that playing the same opponents is not necessarily completely equitable. There is also no scheduled showcase final match unless (by coincidence) two competitors meet in the last match of the tournament, with the result of that match determining

824-477: A competitor's chance of ultimate victory. Final records of participants are more accurate, in the sense that they represent the results over a longer period against the same opposition. The system is also better for ranking all participants, not just determining the winner. This is helpful to determine the final rank of all competitors, from strongest to weakest, for purposes of qualification for another stage or competition as well as for prize money. In team sports,

927-493: A comprehensive international study. Such deaths include deaths due to healthcare capacity constraints and priorities, as well as reluctance to seek care (to avoid possible infection). Further research may help distinguish the proportions directly caused by COVID-19 from those caused by indirect consequences of the pandemic. In May 2022, the WHO estimated the number of excess deaths by the end of 2021 to be 14.9 million compared to 5.4 million reported COVID-19 deaths, with

1030-488: A hard court variant, which has prompted calls from some players (such as Rafael Nadal ) to feature a greater variety of surfaces, including clay courts . For many years, the doubles event was held as a separate tournament staged the week after the singles competition, but more recently both events have been held together during the same week and in the same venue. In 2020, amid the COVID-19 pandemic and in an effort to reduce

1133-590: A large number of people". During the COVID-19 pandemic, as with other pandemics, the meaning of this term has been challenged. The end of a pandemic or other epidemic only rarely involves the total disappearance of a disease, and historically, much less attention has been given to defining the ends of epidemics than their beginnings. The ends of particular epidemics have been defined in a variety of ways, differing according to academic field, and differently based on location and social group. An epidemic's end can be considered

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1236-484: A lower-placed qualifier is perceived to be easier than for a higher-placed one). Four pairs in the 2012 Olympics Women's doubles badminton , having qualified for the next round, were ejected from the competition for attempting to lose in the round robin stage to avoid compatriots and better ranked opponents. The round robin stage at the Olympics was a new introduction, and these potential problems were readily known prior to

1339-448: A median range of 0.24% to 1.49%. IFRs rise as a function of age (from 0.002% at age 10 and 0.01% at age 25, to 0.4% at age 55, 1.4% at age 65, 4.6% at age 75, and 15% at age 85). These rates vary by a factor of ≈10,000 across the age groups. For comparison, the IFR for middle-aged adults is two orders of magnitude higher than the annualised risk of a fatal automobile accident and much higher than

1442-668: A new jointly-owned event called the "Tennis Masters Cup". As with the Masters Grand Prix and the ATP Tour World Championships, the Tennis Masters Cup was contested by eight players and teams. However, the player or team ranked number eight in the ATP Race world rankings was not guaranteed a spot: if a player or team won one of the year's majors and finished the year ranked from ninth to twentieth, they were included in

1545-815: A random sample have consistently found that total infections considerably exceed the reported case counts. Many countries, early on, had official policies to not test those with only mild symptoms. The strongest risk factors for severe illness are obesity, complications of diabetes , anxiety disorders, and the total number of conditions. During the start of the COVID-19 pandemic it was not clear whether young people were less likely to be infected, or less likely to develop symptoms and be tested. A retrospective cohort study in China found that children and adults were just as likely to be infected. Among more thorough studies, preliminary results from 9 April 2020 found that in Gangelt ,

1648-437: A round in which players meets each other. For example, player 7 plays against player 11 in round 4. If a player meets itself, then this shows a bye or a game against player n. All games in a round constitutes a diagonal in the table. The above schedule can also be represented by a graph, as shown below: Both the graph and the schedule were reported by Édouard Lucas in as a recreational mathematics puzzle. Lucas, who describes

1751-497: A round, a non-leftmost position (not including 1 {\displaystyle 1} ) can only be taken by competitors of a fixed distance. In round 1 {\displaystyle 1} of the example, in the second position competitor 2 {\displaystyle 2} plays against 13 {\displaystyle 13} , their distance is 2 {\displaystyle 2} . In round 2 {\displaystyle 2} , this position

1854-540: A schedule where player 14 has a fixed position, and all other players are rotated counterclockwise n 2 {\displaystyle {\frac {n}{2}}} positions. This schedule is easily generated manually. To construct the next round, the last player, number 8 in the first round, moves to the head of the table, followed by player 9 against player 7, player 10 against 6, until player 1 against player 2. Arithmetically, this equates to adding n 2 {\displaystyle {\frac {n}{2}}} to

1957-457: A social phenomenon, not just a biological one. Time reported in March 2024 that expert opinions differ on whether or not COVID-19 is considered endemic or pandemic, and that the WHO continued to call the disease a pandemic on its website. During the initial outbreak in Wuhan , the virus and disease were commonly referred to as "coronavirus", "Wuhan coronavirus", "the coronavirus outbreak" and

2060-619: A straight knockout system. The top one, two, or occasionally three teams in these groups then proceed to a straight knockout stage for the remainder of the tournament. In the circle of death it is possible that no champion emerges from a round-robin tournament, even if there is no draw, but most sports have tie-breaker systems which resolve this. Round-robins can suffer from being too long compared to other tournament types, and with later scheduled games potentially not having any substantial meaning. They may also require tie-breaking procedures. Swiss system tournaments attempt to combine elements of

2163-521: A table. In France this is called the Carousel -Berger system (Système Rutch-Berger). The schedule can also be used for "asynchronous" round-robin tournaments where all games take place at different times (for example, because there is only one venue). The games are played from left to right in each round, and from the first round to the last. When the number of competitors is even, this schedule performs well with respect to quality and fairness measures such as

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2266-451: A test. Conversely, deaths of people who died from underlying conditions following a positive test may be included. Countries such as Belgium include deaths from suspected cases, including those without a test, thereby increasing counts. Official death counts have been claimed to underreport the actual death toll, because excess mortality (the number of deaths in a period compared to a long-term average) data show an increase in deaths that

2369-416: A tournament of 16 teams can be completed in just 4 rounds (i.e. 15 matches) in a knockout format; a double elimination tournament format requires 30 (or 31) matches, but a round-robin would require 15 rounds (i.e. 120 matches) to finish if each competitor faces each other once. Other issues stem from the difference between the theoretical fairness of the round robin format and practice in a real event. Since

2472-555: A variety of tiebreaker criteria. Frequently, pool stages within a wider tournament are conducted on a round-robin basis. Examples with single round-robin scheduling include the FIFA World Cup , UEFA European Football Championship , and UEFA Cup (2004–2009) in football, Super Rugby ( rugby union ) in the Southern Hemisphere during its past iterations as Super 12 and Super 14 (but not in its later 15- and 18-team formats),

2575-613: Is a simple algorithm to create a schedule for a round-robin tournament. All competitors are assigned to numbers, and then paired in the first round: Next, one of the competitors in the first or last column of the table is fixed (number one in this example) and the others rotated clockwise one position: This is repeated until when the next iteration would lead back to the initial pairings: With an even number n {\displaystyle n} of competitors this algorithm realizes every possible combination of them (equivalently, that all pairs realized are pairwise different). First,

2678-435: Is always on the first row. If, say, competitors 3 and 8 were unable to fulfil their fixture in the third round, it would need to be rescheduled outside the other rounds, since both competitors would already be facing other opponents in those rounds. More complex scheduling constraints may require more complex algorithms. This schedule is applied in chess and draughts tournaments of rapid games, where players physically move round

2781-518: Is associated with COVID-19 and is reported in as many as 88% of cases. The disease is mainly transmitted via the respiratory route when people inhale droplets and small airborne particles (that form an aerosol ) that infected people exhale as they breathe, talk, cough, sneeze, or sing. Infected people are more likely to transmit COVID-19 when they are physically close to other non-infected individuals. However, infection can occur over longer distances, particularly indoors. SARS‑CoV‑2 belongs to

2884-600: Is discouraged altogether by the World Health Organization (WHO), due to limited evidence of its efficacy. The severity of COVID-19 varies. It may take a mild course with few or no symptoms, resembling other common upper respiratory diseases such as the common cold . In 3–4% of cases (7.4% for those over age 65) symptoms are severe enough to cause hospitalisation. Mild cases typically recover within two weeks, while those with severe or critical diseases may take three to six weeks to recover. Among those who have died,

2987-691: Is even, then in each of ( n − 1 ) {\displaystyle (n-1)} rounds, n 2 {\displaystyle {\begin{matrix}{\frac {n}{2}}\end{matrix}}} games can be run concurrently, provided there exist sufficient resources (e.g. courts for a tennis tournament). If n {\displaystyle n} is odd, there will be n {\displaystyle n} rounds, each with n − 1 2 {\displaystyle {\begin{matrix}{\frac {n-1}{2}}\end{matrix}}} games, and one competitor having no game in that round. The circle method

3090-1054: Is held by competitors 14 {\displaystyle 14} and 12 {\displaystyle 12} , also having distance 2 {\displaystyle 2} , etc. Similarly, the next position ( 3 {\displaystyle 3} against 12 {\displaystyle 12} in round 1 {\displaystyle 1} , 2 {\displaystyle 2} against 11 {\displaystyle 11} in round 2 {\displaystyle 2} , etc.) can only hold distance- 4 {\displaystyle 4} competitors. For every k < n 2 {\displaystyle k<{\frac {n}{2}}} , there are exactly n − 1 {\displaystyle n-1} pairs of distance k {\displaystyle k} . There are n − 1 {\displaystyle n-1} rounds and they all realize one distance- k {\displaystyle k} pair at

3193-439: Is intended to provide acquired immunity against severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), the virus that causes coronavirus disease 2019 ( COVID-19 ). Prior to the COVID-19 pandemic, an established body of knowledge existed about the structure and function of coronaviruses causing diseases like severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). This knowledge accelerated

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3296-497: Is never used when one participant plays others an unequal number of times, as is the case in almost all of the major North American professional sports leagues. In the United Kingdom , a round-robin tournament has been called an American tournament in sports such as tennis or billiards which usually have single-elimination (or "knockout") tournaments, although this is now rarely done. A round-robin tournament with four players

3399-485: Is not explained by COVID-19 deaths alone. Using such data, estimates of the true number of deaths from COVID-19 worldwide have included a range from 18.2 to 33.5 million (≈27.4 million) by 18 November 2023 by The Economist , as well as over 18.5 million by 1 April 2023 by the Institute for Health Metrics and Evaluation and ≈18.2 million (earlier) deaths between 1 January 2020, and 31 December 2021, by

3502-413: Is sometimes called "quad" or "foursome". In sports with a large number of competitive matches per season, double round-robins are common. Most association football leagues in the world are organized on a double round-robin basis, in which every team plays all others in its league once at home and once away. This system is also used in qualification for major tournaments such as the FIFA World Cup and

3605-408: Is the fairest way to determine the champion from among a known and fixed number of contestants. Each contestant, whether player or team, has equal chances against all other opponents because there is no prior seeding of contestants that will preclude a match between any given pair. The element of luck is seen to be reduced as compared to a knockout system since one or two bad performances need not ruin

3708-480: Is the men's premier indoor event of the season, only in three editions it was played outdoors; 1974, 2003 and 2004. The 2024 ATP Finals has a total prize money pool of $ 15,250,000, an increase of 1.67% compared to 2023 and the same total as the WTA Finals for the first time since 2015. The tournament rewards the following points and prize money, per victory (Doubles' prize money is per team): Additional prizes include

3811-452: Is the ratio of deaths to diagnoses. This metric can be misleading because of the delay between symptom onset and death and because testing focuses on symptomatic individuals. Based on Johns Hopkins University statistics, the global CFR was 1.02 percent (6,881,955 deaths for 676,609,955 cases) as of 10 March 2023. The number varies by region and has generally declined over time. Several variants have been named by WHO and labelled as

3914-406: Is the seventh known coronavirus to infect people, after 229E , NL63 , OC43 , HKU1 , MERS-CoV , and the original SARS-CoV . The standard method of testing for presence of SARS-CoV-2 is a nucleic acid test , which detects the presence of viral RNA fragments. As these tests detect RNA but not infectious virus, its "ability to determine duration of infectivity of patients is limited." The test

4017-614: Is typically done on respiratory samples obtained by a nasopharyngeal swab ; however, a nasal swab or sputum sample may also be used. The WHO has published several testing protocols for the disease. Preventive measures to reduce the chances of infection include getting vaccinated, staying at home or spending more time outdoors, avoiding crowded places, keeping distance from others, wearing a mask in public, ventilating indoor spaces, managing potential exposure durations, washing hands with soap and water often and for at least twenty seconds, practising good respiratory hygiene, and avoiding touching

4120-519: The 2024 title, Sinner earned a record $ 4,881,100, the highest payout for a tournament winner in tennis. In 2022 , Rajeev Ram and Joe Salisbury claimed $ 930,300, the highest payout in doubles history. The ATP Finals is the fifth iteration of a championship which began in 1970. It was originally known as the Masters Grand Prix and was part of the Grand Prix tennis circuit . It was organised by

4223-560: The 2025 ICC Champions Trophy . In a more extreme example, the KBO League in baseball plays a 16-fold round robin, with each of the 10 teams playing each other 16 times for a total of 144 games per team. LIDOM (Baseball Winter League in the Dominican Republic) plays an 18-fold round robin as a semi final tournament between four classified teams. Group tournaments rankings usually go by number of matches won and drawn, with any of

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4326-630: The Cricket World Cup along with Indian Premier League , major Twenty-20 Cricket tournament, and many American football college conferences , such as the Conference USA (which currently has 9 members). The group phases of the UEFA club competitions and Copa Libertadores are contested as a double round-robin, as are most basketball leagues outside the United States, including the regular season of

4429-520: The EuroLeague (as well as its former Top 16 phase); the United Football League has used a double round-robin for both its 2009 and 2010 seasons. Season ending tennis tournaments also use a round robin format prior to the semi on stages. The champion in a round-robin tournament is the contestant that wins the most games, except when draws are possible. In theory, a round-robin tournament

4532-501: The Huanan Seafood Wholesale Market there, but it is possible that human-to-human transmission began earlier. Molecular clock analysis suggests that the first cases were likely to have been between October and November 2019. The scientific consensus is that the virus is most likely of a zoonotic origin, from bats or another closely related mammal. While other explanations such as speculations that SARS-CoV-2

4635-407: The Institute for Health Metrics and Evaluation estimating the true number of cases as of early 2022 to be in the billions. One measure that public health officials and policymakers have used to monitor the pandemic and guide decision-making is the test positivity rate ("percent positive"). According to Johns Hopkins in 2020, one benchmark for a "too high" per cent positive is 5%, which was used by

4738-597: The basic reproduction number (R 0 ) for COVID-19 in January 2020 were between 1.4 and 2.5, but a subsequent analysis claimed that it may be about 5.7 (with a 95 per cent confidence interval of 3.8 to 8.9). In December 2021, the number of cases continued to climb due to several factors, including new COVID-19 variants. As of that 28   December, 282,790,822 individuals worldwide had been confirmed as infected. As of 14 April 2022 , over 500 million cases were confirmed globally. Most cases are unconfirmed, with

4841-474: The variants of interest as specified by the World Health Organization are BA.2.86 and JN.1, and the variants under monitoring are JN.1.7, KP.2, KP.3, KP.3.1.1, JN.1.18, LB.1, and XEC. Symptoms of COVID-19 are variable, ranging from mild symptoms to severe illness. Common symptoms include headache, loss of smell and taste , nasal congestion and runny nose , cough, muscle pain , sore throat , fever, diarrhoea , and breathing difficulties . People with

4944-429: The "Wuhan coronavirus outbreak", with the disease sometimes called "Wuhan pneumonia ". In January 2020, the WHO recommended 2019-nCoV and 2019-nCoV acute respiratory disease as interim names for the virus and disease per 2015 international guidelines against using geographical locations (e.g. Wuhan, China), animal species, or groups of people in disease and virus names in part to prevent social stigma . WHO finalised

5047-597: The ATP Finals trophy and the ATP year-end No. 1 trophy, all made by London-based silversmiths Thomas Lyte . Note: Titles, won by a team of players from same country , count as one title, not two. Round-robin tournament A round-robin tournament or all-play-all tournament is a competition format in which each contestant meets every other participant, usually in turn. A round-robin contrasts with an elimination tournament , wherein participants are eliminated after

5150-671: The International Lawn Tennis Federation ( ILTF ) and ran alongside the competing WCT Finals from 1971 to 1989. The Masters was a year-end showpiece event between the best players on the men's tour, but did not count for any world ranking points. In 1990, the Association of Tennis Professionals (ATP) took over the running of the men's tour and replaced the Masters with the "ATP Tour World Championships". World ranking points were now at stake, with an undefeated champion earning

5253-455: The Tennis Masters Cup instead. If two outside the top eight won majors, the higher-ranked of the two in the world rankings took the final spot. This accommodation for major champions continues in the event's current form. In 2009 , the championship was renamed the "ATP World Tour Finals" and was held at The O2 Arena in London. The contract ran through 2013, but was extended multiple times until it

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5356-636: The WHO in the past. As of 10 March 2023, more than 6.88   million deaths had been attributed to COVID-19. The first confirmed death was in Wuhan on 9 January 2020. These numbers vary by region and over time, influenced by testing volume, healthcare system quality, treatment options, government response, time since the initial outbreak, and population characteristics, such as age, sex, and overall health. Multiple measures are used to quantify mortality. Official death counts typically include people who died after testing positive. Such counts exclude deaths without

5459-419: The WHO, US, European Union, and Australia. On 12 November 2022, the WHO released its Global Vaccine Market Report. The report indicated that "inequitable distribution is not unique to COVID-19 vaccines"; countries that are not economically strong struggle to obtain vaccines. On 14 November 2022, the first inhalable vaccine was introduced, developed by Chinese biopharmaceutical company CanSino Biologics , in

5562-446: The algorithm obviously realizes every pair of competitors if one of them equals 1 {\displaystyle 1} (the non-moving competitor). Next, for pairs of non- 1 {\displaystyle 1} competitors, let their distance be the number k < n 2 {\displaystyle k<{\frac {n}{2}}} of times the rotation has to be carried out in order that one competitor arrives at

5665-535: The amount of rest between games. On the other hand, when the number of competitors is odd, it does not perform so well and a different schedule is superior with respect to these measures. Alternatively Berger tables, named after the Austrian chess master Johann Berger , are widely used in the planning of tournaments. Berger published the pairing tables in his two Schach-Jahrbücher (Chess Annals), with due reference to its inventor Richard Schurig. This constitutes

5768-472: The beginning of the Open Era . Novak Djokovic holds the record for the most singles titles with seven, while Peter Fleming and John McEnroe jointly hold the record for the most doubles titles with seven (all won consecutively as a team). In the tournament's current format, the champion can earn a maximum of 1,500 ranking points, if they win the event after going undefeated in the round-robin stage. By winning

5871-448: The broad family of viruses known as coronaviruses . It is a positive-sense single-stranded RNA (+ssRNA) virus, with a single linear RNA segment. Coronaviruses infect humans, other mammals, including livestock and companion animals, and avian species. Human coronaviruses are capable of causing illnesses ranging from the common cold to more severe diseases such as Middle East respiratory syndrome (MERS, fatality rate ≈34%). SARS-CoV-2

5974-630: The centre of a major infection cluster in Germany, 15 per cent of a population sample tested positive for antibodies . Screening for COVID-19 in pregnant women in New York City , and blood donors in the Netherlands, found rates of positive antibody tests that indicated more infections than reported. Seroprevalence -based estimates are conservative as some studies show that persons with mild symptoms do not have detectable antibodies. Initial estimates of

6077-435: The championship. A notable instance of such an event was the 1950 FIFA World Cup match between Uruguay and Brazil . Further issues arise where a round-robin is used as a qualifying round within a larger tournament. A competitor already qualified for the next stage before its last game may either not try hard (in order to conserve resources for the next phase) or even deliberately lose (if the scheduled next-phase opponent for

6180-746: The city of Shanghai, China. For the first two years of the pandemic, no specific and effective treatment or cure was available. In 2021, the European Medicines Agency's (EMA) Committee for Medicinal Products for Human Use (CHMP) approved the oral antiviral protease inhibitor , Paxlovid (nirmatrelvir plus the HIV antiviral ritonavir ), to treat adult patients. FDA later gave it an EUA. Most cases of COVID-19 are mild. In these, supportive care includes medication such as paracetamol or NSAIDs to relieve symptoms (fever, body aches, cough), adequate intake of oral fluids and rest. Good personal hygiene and

6283-537: The competition, his results are considered separately, i.e. the alternate does not inherit the results of the player he is replacing. If an alternate's round-robin results qualify him for the semifinals, then he may continue into the single-elimination rounds. Unlike other events on the ATP Tour , the ATP Finals is not a straightforward single-elimination tournament. The eight players and teams are divided into two groups of four and each play three round-robin matches against

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6386-581: The continental tournaments (e.g. UEFA European Championship , CONCACAF Gold Cup , AFC Asian Cup , CONMEBOL Copa América and CAF Cup of Nations ). There are also round-robin cricket , bridge , chess , draughts , go , ice hockey , curling , and Scrabble tournaments. The World Chess Championship decided in 2005 and in 2007 on an eight-player double round-robin tournament where each player faces every other player once as white and once as black. There has been several major international cricket tournaments held in this format including ICC events, including

6489-427: The court surface and the court's illumination. In recent years it has been played on indoor hard courts, however, indoor carpet was used in some previous editions. On one occasion, when Melbourne hosted the event in 1974 , the grass courts of Kooyong Stadium were used; the tournament was staged only 1–2 weeks before the 1975 Australian Open , which was also played on grass. Apart from 1974, all tournaments have been on

6592-480: The cumulative number of infected individuals (including asymptomatic and undiagnosed infections and excluding vaccinated infected individuals). It is expressed in percentage points. Other studies refer to this metric as the infection fatality risk . In November 2020, a review article in Nature reported estimates of population-weighted IFRs for various countries, excluding deaths in elderly care facilities, and found

6695-441: The development of various vaccine platforms during early 2020. The initial focus of SARS-CoV-2 vaccines was on preventing symptomatic and severe illness. The COVID-19 vaccines are widely credited for their role in reducing the severity and death caused by COVID-19. As of March 2023, more than 5.5 billion people had received one or more doses (11.8 billion in total) in over 197 countries. The Oxford-AstraZeneca vaccine

6798-513: The eyes, nose, or mouth with unwashed hands. Those diagnosed with COVID-19 or who believe they may be infected are advised by healthcare authorities to stay home except to get medical care, call ahead before visiting a healthcare provider, wear a face mask before entering the healthcare provider's office and when in any room or vehicle with another person, cover coughs and sneezes with a tissue, regularly wash hands with soap and water and avoid sharing personal household items. A COVID-19 vaccine

6901-450: The following years: Since 2019, the group standings at the end of the round-robin stage are determined by, in order: If some players are tied, the following tiebreakers are used depending on how many players are tied (two or three): If two players are tied , then: If three players are tied , then the following tiebreakers are used, in order, until all three players are no longer tied OR until only two players are tied, at which point

7004-525: The general public beginning in December 2020, made available through government and international programs such as COVAX , aiming to provide vaccine equity . Treatments include novel antiviral drugs and symptom control. Common mitigation measures during the public health emergency included travel restrictions , lockdowns , business restrictions and closures, workplace hazard controls , mask mandates , quarantines, testing systems, and contact tracing of

7107-465: The groups, the eight players and teams are seeded according to rank. The first and second seeds are placed in Group A and Group B, respectively. The remaining seeds are drawn in pairs (third and fourth, fifth and sixth, seventh and eighth); the first of the pair to be drawn goes to Group A and the other to Group B, and so on. The format described above has been in place for all editions of the tournament except

7210-413: The highest-ranked player who has not otherwise qualified for the event. If both alternate spots are available, they are awarded to the two highest-ranked players who did not otherwise qualify for the event. An alternate can replace a player who withdraws before the round-robin stage is over, so long as the player who withdraws still has at least one round-robin match left to play. When an alternate enters

7313-657: The infected. The pandemic caused severe social and economic disruption around the world, including the largest global recession since the Great Depression . Widespread supply shortages , including food shortages , were caused by supply chain disruptions and panic buying . Reduced human activity led to an unprecedented temporary decrease in pollution . Educational institutions and public areas were partially or fully closed in many jurisdictions, and many events were cancelled or postponed during 2020 and 2021. Telework became much more common for white-collar workers as

7416-484: The issue of respiratory failure. Existing drugs such as hydroxychloroquine , lopinavir/ritonavir , and ivermectin are not recommended by US or European health authorities, as there is no good evidence they have any useful effect. The antiviral remdesivir is available in the US, Canada, Australia, and several other countries, with varying restrictions; however, it is not recommended for use with mechanical ventilation, and

7519-399: The main sponsor for the tournament through 2020. In September 2020, Nitto Denko announced it will extend its title partnership of the ATP Finals for another five years, until 2025. The criteria to qualify for the ATP Finals are as follows: Two alternates also attend the ATP Finals. If the first alternate has already been selected according to (3) mentioned above, then the second alternate is

7622-576: The majority of the unreported 9.5 million deaths believed to be direct deaths due the virus, rather than indirect deaths. Some deaths were because people with other conditions could not access medical services . A December 2022 WHO study estimated excess deaths from the pandemic during 2020 and 2021, again concluding ≈14.8 million excess early deaths occurred, reaffirming and detailing their prior calculations from May as well as updating them, addressing criticisms. These numbers do not include measures like years of potential life lost and may make

7725-403: The method as simple and ingenious , attributes the solution to Felix Walecki, a teacher at Lycée Condorcet . Lucas also included an alternative solution by means of a sliding puzzle . To easily remember this method, the following mnemonic can be used. Starting from the first round, the next round is constructed: and then, If the number of players is odd, the player in the first venue gets

7828-494: The number of staff on-site, the ATP introduced live electronic line-calling powered by Hawk-Eye Live . Instead of line umpires, the system detects the relevant movements of the player and where the ball bounces on court. A pre-recorded voice announces "Out", "Fault", and "Foot fault". Also, video review was also introduced for suspected double bounces, touches, and other reviewable calls. The tournament has traditionally been sponsored by

7931-495: The official names COVID-19 and SARS-CoV-2 on 11 February 2020. Tedros Adhanom Ghebreyesus explained: CO   for corona , VI   for virus , D   for disease and 19 for when the outbreak was first identified (31 December 2019). WHO additionally uses "the COVID-19 virus" and "the virus responsible for COVID-19" in public communications. WHO named variants of concern and variants of interest using Greek letters . The initial practice of naming them according to where

8034-448: The others in their group. After the round-robin stage, the top two performers in each group advance to the semifinals in a knock-out stage. The two winners of the semifinals play a final to determine the champion. In this format, it is theoretically possible to advance to the semifinals with two round-robin losses, but no player in the history of the singles tournament has won the title after losing more than one round-robin match. To create

8137-534: The outbreak a public health emergency of international concern (PHEIC) on 30 January 2020, and assessed the outbreak as having become a pandemic on 11 March. COVID-19 symptoms range from asymptomatic to deadly, but most commonly include fever, sore throat , nocturnal cough , and fatigue. Transmission of the virus is often through airborne particles . Mutations have produced many strains (variants) with varying degrees of infectivity and virulence . COVID-19 vaccines were developed rapidly and deployed to

8240-407: The pandemic 2021's leading cause of death . The time between symptom onset and death ranges from   6 to 41 days, typically about 14 days. Mortality rates increase as a function of age. People at the greatest mortality risk are the elderly and those with underlying conditions. The infection fatality ratio (IFR) is the cumulative number of deaths attributed to the disease divided by

8343-491: The pandemic evolved. Misinformation circulated through social media and mass media , and political tensions intensified . The pandemic raised issues of racial and geographic discrimination , health equity , and the balance between public health imperatives and individual rights . The WHO ended the PHEIC for COVID-19 on 5 May 2023. The disease has continued to circulate, but as of 2024, experts were uncertain as to whether it

8446-415: The population's age structure and the age-specific pattern of infections. There have also been reviews that have compared the fatality rate of this pandemic with prior pandemics, such as MERS-CoV. For comparison the infection mortality rate of seasonal flu in the United States is 0.1%, which is 13 times lower than COVID-19. Another metric in assessing death rate is the case fatality ratio (CFR), which

8549-496: The position the other had. In the example given ( n = 14 {\displaystyle n=14} ), 2 {\displaystyle 2} has distance 1 {\displaystyle 1} to 3 {\displaystyle 3} and to 14 {\displaystyle 14} and it has distance 6 {\displaystyle 6} to 8 {\displaystyle 8} and to 9 {\displaystyle 9} . In

8652-400: The previous row, with the exception of player n {\displaystyle n} . When the result of the addition is greater than ( n − 1 ) {\displaystyle (n-1)} , then subtract ( n − 1 ) {\displaystyle (n-1)} from the sum. This schedule can also be represented as a (n-1, n-1) table, expressing

8755-458: The risk of dying from seasonal influenza . In December 2020, a systematic review and meta-analysis estimated that population-weighted IFR was 0.5% to 1% in some countries (France, Netherlands, New Zealand, and Portugal), 1% to 2% in other countries (Australia, England, Lithuania, and Spain), and about 2.5% in Italy. This study reported that most of the differences reflected corresponding differences in

8858-406: The round-robin and elimination formats, to provide a worthy champion using fewer rounds than a round-robin, while allowing draws and losses. The main disadvantage of a round robin tournament is the time needed to complete it. Unlike a knockout tournament where half of the participants are eliminated after each round, a round robin requires one round less than the number of participants. For instance,

8961-521: The round-robin major league champions are generally regarded as the "best" team in the land, rather than the cup winners, whose tournaments usually follow a single-elimination format. Moreover, in tournaments such as the FIFA or ICC World Cups, a first round stage consisting of a number of mini round robins between groups of 4 teams guards against the possibility of a team travelling possibly thousands of miles only to be eliminated after just one poor performance in

9064-496: The same infection may have different symptoms, and their symptoms may change over time. Three common clusters of symptoms have been identified: one respiratory symptom cluster with cough, sputum , shortness of breath, and fever; a musculoskeletal symptom cluster with muscle and joint pain, headache, and fatigue; a cluster of digestive symptoms with abdominal pain, vomiting, and diarrhoea. In people without prior ear, nose, and throat disorders, loss of taste combined with loss of smell

9167-527: The same number of points they would earn for winning one of the four Grand Slam events. The ITF, who continued to run the Grand Slam tournaments, created a rival year-end event known as the Grand Slam Cup , which was contested by the 16 players with the best records in the Grand Slam tournaments of the season (1990–99). In December 1999, the ATP and ITF agreed to discontinue the two separate events and create

9270-408: The same position. Clearly, these pairs are pairwise different. The conclusion is that every distance- k {\displaystyle k} pair is realized. This holds for every k {\displaystyle k} , hence, every pair is realized. If there are an odd number of competitors, a dummy competitor can be added, whose scheduled opponent in a given round does not play and has

9373-603: The teams. This famously happened during the 1994 FIFA World Cup Group E , where all four teams finished with a record of one win, one draw, and one loss. This phenomenon is analogous to the Condorcet paradox in voting theory. If n {\displaystyle n} is the number of competitors, a pure round robin tournament requires n 2 ( n − 1 ) {\displaystyle {\begin{matrix}{\frac {n}{2}}\end{matrix}}(n-1)} games. If n {\displaystyle n}

9476-411: The time from symptom onset to death has ranged from two to eight weeks. Prolonged prothrombin time and elevated C-reactive protein levels on admission to the hospital are associated with severe course of COVID-19 and with a transfer to intensive care units (ICU). Between 5% and 50% of COVID-19 patients experience long COVID , a condition characterised by long-term consequences persisting after

9579-463: The title sponsor of the tour; however, in 1990–2008 the competition was not sponsored, even though the singles portion of the event, as part of the ATP Tour, was sponsored by IBM . In 2009, the tournament gained Barclays PLC as its title sponsor. Barclays confirmed in 2015 that they would not renew their sponsorship deal once it expires in 2016. On 25 May 2017, it was announced that Nitto Denko would be

9682-573: The top left corner by repeating the sequence of numbers from 1 up to n − 1 {\displaystyle n-1} . Here is an example table for 7 or 8 competitors: COVID-19 pandemic The COVID-19 pandemic (also known as the coronavirus pandemic and COVID pandemic ), caused by severe acute respiratory syndrome coronavirus 2 ( SARS-CoV-2 ), began with an outbreak of COVID-19 in Wuhan , China, in December 2019. It spread to other areas of Asia, and then worldwide in early 2020. The World Health Organization (WHO) declared

9785-435: The tournament; changes were made prior to the next Olympics to prevent a repeat of these events. Another disadvantage, especially in smaller round-robins, is the "circle of death", where teams cannot be separated on a head-to-head record. In a three-team round-robin, where A defeats B, B defeats C, and C defeats A, all three competitors will have a record of one win and one loss, and a tiebreaker will need to be used to separate

9888-416: The two-player tie is broken by the head-to-head round robin result: When calculating tiebreakers, a match that ended in a retirement is counted as a 0–2 sets loss for the retiring player and a 2–0 sets win for their opponent, regardless of the actual score when the retirement occurred. When calculating the "Highest % of games won" tiebreaker, a match that ended in a retirement is disregarded. ATP Finals

9991-694: The typical convalescence period of the disease. The most commonly reported clinical presentations are fatigue and memory problems, as well as malaise , headaches, shortness of breath , loss of smell, muscle weakness , low fever and cognitive dysfunction . Many countries attempted to slow or stop the spread of COVID-19 by recommending, mandating or prohibiting behaviour changes, while others relied primarily on providing information. Measures ranged from public advisories to stringent lockdowns. Outbreak control strategies are divided into elimination and mitigation. Experts differentiate between elimination strategies (known as " zero-COVID ") that aim to completely stop

10094-543: The variants were identified (e.g. Delta began as the " Indian variant") is no longer common. A more systematic naming scheme reflects the variant's PANGO lineage (e.g., Omicron 's lineage is B.1.1.529) and is used for other variants. SARS-CoV-2 is a virus closely related to bat coronaviruses , pangolin coronaviruses, and SARS-CoV . The first known outbreak (the 2019–2020 COVID-19 outbreak in mainland China ) started in Wuhan , Hubei, China, in December 2019. Many early cases were linked to people who had visited

10197-451: The victor is gradually arrived at through multiple rounds of play, teams who perform poorly, who might have been quickly eliminated from title contention, are forced to play out their remaining games. Thus games are played late in the competition between competitors with no remaining chance of success. Moreover, some later matches will pair one competitor who has something left to play for against another who does not. It may also be possible for

10300-443: Was accidentally released from a laboratory have been proposed, as of 2021 these were not supported by evidence. Official "case" counts refer to the number of people who have been tested for COVID-19 and whose test has been confirmed positive according to official protocols whether or not they experienced symptomatic disease. Due to the effect of sampling bias , studies which obtain a more accurate number by extrapolating from

10403-574: Was last held there in 2020. In 2017 the event was renamed the "ATP Finals ." In April 2019, the ATP announced that Turin would host the ATP Finals from 2021 to 2025. For most of its history, the event has been considered the most important indoor tennis tournament in the world (there were a few exceptions when the event was held outdoors: 1974 in Melbourne & 2003–04 in Houston). The indoor atmosphere allows for controlled conditions of play, both in terms of

10506-457: Was still a pandemic. Pandemics and their ends are not well-defined, and whether or not one has ended differs according to the definition used. As of 24 November 2024, COVID-19 has caused 7,075,455 confirmed deaths. The COVID-19 pandemic ranks as the fifth- deadliest pandemic or epidemic in history . In epidemiology , a pandemic is defined as "an epidemic occurring over a very wide area, crossing international boundaries, and usually affecting

10609-502: Was the most widely used. According to a June 2022 study, COVID-19 vaccines prevented an additional 14.4 million to 19.8 million deaths in 185 countries and territories from 8 December 2020 to 8 December 2021. On 8 November 2022, the first recombinant protein-based COVID-19 vaccine (Novavax's booster Nuvaxovid ) was authorised for use in adults in the United Kingdom. It has subsequently received endorsement/authorisation from

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