Epidemiology

Main articles: 2019–20 coronavirus pandemic by country and territory2019–20 coronavirus pandemic cases/WHO situation reports, and 2019–20 coronavirus pandemic deaths/WHO situation reports

The earliest known person with symptoms was soon traced back to December 2019, someone who did not have visible connections with the later wet market’s cluster. Of the early cluster of cases reported in December 2019, two-thirds were found to have a link with the market. On 14 March 2020, a report from the South China Morning Post said that a 55-year-old from Hubei province could have been the first person who contracted the disease, on 17 November.

The earliest known person with symptoms was soon traced back to  December 2019, someone who did not have visible connections with the later wet market‘s cluster.[243][244] Of the early cluster of cases reported in December 2019, two-thirds were found to have a link with the market.[2][245][246] On 14 March 2020, a report from the South China Morning Post said that a 55-year-old from Hubei province could have been the first person who contracted the disease, on 17 November.[247][248]

On 26 February 2020, the WHO reported that, as new cases reportedly dropped in China but suddenly increased in Italy, Iran, and South Korea, the number of new cases outside China had exceeded the number of new cases in China for the first time.[249] There may be substantial underreporting of cases, particularly those with milder symptoms.[250][251] By 26 February, relatively few cases have been reported among youth, with those 19 and under making up 2.4% of cases worldwide.[16][252]

Government sources in Germany and the UK estimate that 60–70% of the population will need to become infected before effective herd immunity can be achieved.[253][254][255]

A scientific paper published from epidemiologists from the University of Oxford modeled the amount of SARS-Cov-2 cases in the United Kingdom and Italy. One out of different scenarios states, that 68% of the population of the United Kingdom were infected by 19 March 2020. For Italy one out of different scenarios assumes, that by 6 March 2020, 80% of the Italian population were infected by SARS-Cov-2.[256][257][258]

Deaths

The time from development of symptoms to death has been between 6 and 41 days, with the most common being 14 days.[16] By 24 March more than 16,700 deaths had been attributed to COVID-19.[259] Most of those who have died were elderly—about 80% of deaths were in those over 60, and 75% had pre-existing health conditions including cardiovascular diseases and diabetes.[260]

The first confirmed death was on 9 January 2020 in Wuhan.[261] The first death outside China occurred on 1 February in the Philippines,[262][263] and the first death outside Asia was in France on 14 February.[264] By 28 February, outside mainland China, more than a dozen deaths each were recorded in Iran, South Korea, and Italy.[265][266][267] By 13 March, more than forty countries and territories had reported deaths, on every continent except Antarctica.[268]

A number of measures of mortality are being tracked. The WHO estimated the global crude mortality rate (cumulative deaths divided by cumulative reported infections) to be 3% to 4% as of 6 March 2020[269]. The case-fatality rate (CFR) is the proportion of persons diagnosed with a particular condition (cases) who subsequently die from that condition,[270] having been adjusted for the time lapse between infection and death;[271][272] estimates of the CFR vary from 1.4% to 2.3%.[273][274] The infection mortality rate (IFR) incorporates a further adjustment to allow for undiagnosed and/or asymptomatic infections; as at 22 March 2020 it has been estimated at 0.20%.[275]

Over time, estimates for the CFR in China decreased markedly from 17.3% (for those with symptom onset 1–10 January 2020) to 0.7% (for those with symptom onset after 1 February 2020).[252]

Diagrams

  • Total confirmed cases of COVID-19 per million people, 25 March 2020[276]
  • Total confirmed deaths due to COVID-19 per million people, 25 March 2020[277]
  • Epidemic curve of COVID-19 by date of report
  • Semi-log plot of cumulative incidence of confirmed cases and deaths in China and the rest of the world (ROW)[278][279]
  • Semi-log plot of daily new confirmed cases by region: Hubei Province, mainland China excluding Hubei, the rest of the world (ROW), and the world total[278][279]
  • Semi-log plot of coronavirus daily deaths by region: Hubei Province, mainland China excluding Hubei, the rest of the world (ROW), and the world total[278][279]
  • Semi-log plot of cases in some countries with high growth rates (post-China) with doubling times and three-day projections based on the exponential growth rates
  • Semi-log graph showing the change in total (cumulative) count from the first reported date for the ten most affected countries[280]





Duration

The WHO asserts that this pandemic can be controlled.[11] Predicting the peak and ultimate duration of the outbreak is uncertain and may differ in different places. Maciej Boni of Penn State University stated, “Left unchecked, infectious outbreaks typically plateau and then start to decline when the disease runs out of available hosts. But it’s almost impossible to make any sensible projection right now about when that will be”.[281] Zhong Nanshan, the Chinese government’s senior medical adviser, argued that WHO advice on measures to stop the spread of the virus should be followed everywhere and that “If all countries could get mobilized, it could be over by June.”[281] Adam Kucharski of London School of Hygiene & Tropical Medicine stated that SARS-CoV-2 “is going to be circulating, potentially for a year or two”.[282] According to the Imperial College study led by Neil Ferguson, physical distancing and other measures would be required “until a vaccine becomes available (potentially 18 months or more)”.[283] William Schaffner of Vanderbilt University stated, “I think it’s unlikely that this coronavirus—because it’s so readily transmissible—will disappear completely” and it “might turn into a seasonal disease, making a comeback every year”. The virulence of the comeback would depend on herd immunity and the extent of mutation.[284]