Global Pandemic Trends of COVID-19 in 2020

Background: The novel coronavirus pneumonia (COVID-19) has been global threaten to public health. This paper provides perspective to the decision-making for public health control of the pandemic or the spread of epidemic. Methods: According to the WHO global reported database, we developed and used the number of cumulative cases, and the number of cumulative deaths to calculate and analyze rates of incidence, mortality, and fatality by country, with respect to the 30 highest outbreak (Top 30) countries.

what hemisphere, societal structure and governancy, no matter what folk cultures and what religious beliefs, have been facing immense challenges of public health. Unfortunately, although quarantine, contact tracing, screening, and isolation are effective measures of COVID-19 prevention, particularly whenever integrated together, have been established as effective measures of containment [10] , the pandemic of COVID-19 has not been effectively curbed up to now. While effectively suppression in spread and control has been observed in some countries, as WHO has already pointed out [9] , many countries are struggling with a lack of capacity, some countries are struggling with a lack of resources, and some countries are struggling with a lack of resolve. COVID-19 is even more prevalent in the world from the current development trends. By the time of this analysis (31st December, 2020, European time), the number of cumulative cases with COVID-19 in the world has exceeded 81,475,053 cases, and the deaths has exceeded 1,798,050 cases [11] ; the ability of the virus to spread far beyond these current estimates is certain [5,12] . No one knows how long such a pandemic will last, but 2020 is destined to be only the rst year of this global pandemic.
In order to fully understand the evolution and developmental trends of the COVID-19 epidemic, it is necessary to analyze the dynamic uxes of the incidence and mortality of COVID-19 in various countries around the world. According to COVID-19 epidemic data released by WHO [11] , this paper provides analysis of some of the main indicators of the global COVID-19 epidemic, and provides inferences for the delineating of public health strategies for controlling the pandemic or the spread of epidemic.

Materials And Methods
Data resources WHO has released daily data since 11 January 2020 (starting from 3rd Jan.) on the daily number of new cases, cumulative cases, daily number of new deaths and number of cumulative deaths from COVID-19 by continent and by country (region or territory) through the WHO website (https://www.who.int). It can be obtained by real-time query [11] . To click the "download map data" button at the right bottom of the webpage to download the data le named "WHO-COVID-19-global-data.csv"; or, click directly to the linkage https://covid19.who.int/WHO-COVID-19-global-data.csv, the following main elds (information) can be obtained from this le: date_reported, country_code, country, who_region, new_cases, cumulative_cases, new_deaths, and cumulative_death.

Statistical methods
According to the above data and statistical indicators, the incidence rate, mortality rate, and fatality rate of COVID-19 for 237 countries (regions or territories) in the world are can be calculated. The cumulative numbers of cases and deaths were listed for the top 30 countries in the world (Top 30) from high to low, on the number of cumulative cases. The incidence rate, mortality rate and fatality rate by country (region) of COVID-19 are also ranked and compared among the main countries.

Trends of the epidemic in major countries
China The epidemic of COVID-19 in China started in the beginning of Jan., the total number of cases exceeded 100 on Jan. 19, over 1,000 on Jan. 25, over 10,000 on Feb. 1, over 50,000 on Feb. 13 and over 80,000 on March 2. Since then, the epidemic has been largely controlled and stabilized at a plateau level of cases between 90,000 and 100,000. At the end of 2020, it reached to 96,673 cases, ranking the 78th in the world. The rst death case in China reported on Jan. 11, over 10 cumulative deaths reported after Jan. 23, and 100 deaths reported on Jan. 28. More than 1,000 deaths on Feb. 11, 2000 deaths on Feb. 19, and 3000 deaths on March 5 were reported, successively. On March 17, the cumulative deaths exceed to 4600, and after that the deaths were kept under 4800 until the end of the year. The total deaths due to  in China were 4788 cases in 2020, ranking 43rd in the world. The outbreak and deaths in China in 2020 are shown in Fig. 1A.
The United States Based upon the WHO's data, the rst case reported in the United States (US) was on Jan. 19. The total number of cases exceeded 100 on March 3, more than 1,000 on March 13, 10,000 on March 19, and 100,000 on March 29 (at this point, the total number of cases had overtaken the total number of cases in China). Since then, cases continued to rise. By April 30, there had been more than 1 M cases; on June 13 and July 10 milestones of 2 M and 3 M cases were reached, respectively. There were more than 5 M cases on Aug. 12, 10 M in Nov. 12, and 15 M on Dec. 11. As of Dec. 31, the total number of Russia The total number of cases ranks fourth globally. Its rst case (2 cases) was reported on Jan. 31, over 100 cases on March 18, 10,000 on April 9 and 1 M cases on Sept. 1. The number of cumulative cases in 2020 was 3,159,297.
France The total number of cases ranks fth, and its rst case (3 cases) was reported on Feb. 24. It reached 100 cases on March 1, 10,000 on March 20, and 1 M on Oct. 24. The number of cumulative cases in 2020 was 2,556,708.
The United Kingdom The total number of cases in the United Kingdom (UK) ranks sixth, and its rst case (2 cases) was reported on Feb 1. It reached 100 cases on March 4, 10,000 on March 24, and 1 M on Nov.
1. The number of cumulative cases in 2020 was 2,432,892.
Italy The total number of cases in Italy ranks seventh. Its rst case (2 cases) was reported on Jan. 29. There were more than 100 cases on Feb. 24, 10,000 cases on March 31, and 1 M on Nov. 12. The number of cumulative cases in 2020 was 2,083,689.
Spain The total number of cases ranks eighth. Its rst case (4 cases) was reported on Feb. 2. There were more than 100 cases on March 3, 10,000 on March 16, and 1 M on Oct. 19. The number of cumulative cases in 2020 was 1,893,502.

Discussion
The pneumonia (COVID-19) caused by new coronavirus (SARS-COV-2) has become the most serious and in uential pandemic since the SARS epidemic in 2003 [4,5,6] , and indeed now far exceeds it public health impact. WHO has repeatedly called on all sectors of the world to unite and cooperate to ght against this coronavirus pneumonia. The past 12 months of 2020, fully demonstrated the impact of anti-epidemic practices on the development and changes in epidemic situations under different social systems, social backgrounds and different public health concepts [3,7,13,14] .
We use the WHO's open access data is not only for analyzing the global epidemic status, but also for delineating the development trends of the pandemic of COVID-19. Through the basic epidemic data provided by WHO and the analysis within this paper, we can fully show the ups and downs of the epidemic situation, the "track" or even the "unexpected" situation of the spread of this disease. One can nd from this article that due to the great pathogenicity and infectivity of SARS-COV-2, the whole world has been heavily attacked by the virus, regardless of social and political systems, regardless of the size of the country's wealth, regardless of ethnic and religious habits [7] . According to WHO, COVID-19 has been reported in 222 of 237 countries (regions or territories) in the world at this point of 2020/12/31 [11] .
China is the rst country reported the unknown-pneumonia at the very beginning of the outbreak of new coronavirus infection [1,2,3] . Since the epidemic rst appeared in China, it mandated a needfor understanding of the epidemic rhythm, etiological and clinical features [4,7] . The novel coronavirus pneumonia has took 2 weeks from the early suspicion of discovery (Dec. 31, 2019) to a rough "understanding" of the viral-disease; from "unknown cause" to the determination of the "human transmission" epidemic process. Then it took another week to take protection, isolation, and lockdown measures [3] , resulting in the rapid control (containment) of epidemic within a short period of month (2 incubation periods) [10] . Looking back to analyze the development of the epidemic situation in China, we nd that it took only 6 days from the emergence of more than 100 cumulative cases to 1000 cases; and took 7 days from 1,000 cases to 10,000 cases; and took 12 days from 10,000 cases on Feb. 1 to 50,000 cases on Feb. 13. After another 18 days, the cumulative cases reached 80,000 on March 2. The subsequent epidemics have been fully prevented and controlled [3,4] , and the effects are fully demonstrated on the curves in Fig. 1A.
The US is one of the countries that has been affected by the epidemic later. When 80,000 people in China suffered from COVID-19 in early March, the number of reported cases in US was less than 100. However, when the number of cases in US exceeded 100 on March 3, the number of cumulative cases increased in a speed of exponential growth rate exceeding 1,000, 10,000 and 100,000 cases within every 10 days. From 100,000 cases on March 29 to more than 1 M cases on April 30, taking only one month. In the period of May, the daily COVID-19 new cases seem to be following a downward trend in the US. However, perhaps due to the crowd gathering of "work resumption" [15] and the campaign of social justice ("BML", black lives matter) [16] , the epidemic of COVID-19 reemerged as a serious outbreak, resulting in excess of 2 M cases on June 13, and over 4 M cases on July 25. From mid-Sept., the epidemic curves in the US have continued to climb upwards, and the daily number of new cases has risen from 30,000-40,000 to more than 100,000 on Nov. 6, and even more than 200,000 a day after Dec. 5. The daily deaths due to COVID-19 exceeded 1,000 after mid-Nov., with a maximum of 3,443 a day on Dec. 19. Based upon these available data, we may conclude that the daily increase in the number of new cases and deaths of COVID-19 in the US have not yet shown any dampening in the upward epidemic trends.
The epidemic in India began at the end of Jan., with no new cases reported during the most days of Feb., 2020. New cases appeared again in early March, and the number increased sharply at the end of March. Then the number of cumulative cases increased from 1,000 to 10,000 in two weeks; to 100,000 in ve weeks, and to 1 M in the eight subsequent weeks on July 17. After that, the number of new cases per day has continued to rise, with a highest number of 97,994 cases per day, and the number of cumulative cases of more than 5 M in mid-Sept. Thereafter, the number of new cases gradually declined, and by the end of the year, the number of daily new cases uctuated around 2,000. This may re ect the measures such as the effort of "lockdown" in India [13] . The trend curves of the number of daily deaths and cumulative deaths in India were similar to the curves of the number of daily new cases and the number of cumulative deaths. The COVID-19 epidemic in India seems to have been gradually contained, if this trend can be maintained.
Brazil is another country where the epidemic developed very rapidly [17] , starting after the epidemic situation in China has been controlled. Since the rst case reported at the end of Feb., it took less than 25 days to cross three logarithmic levels of 100 cases, 1,000 cases and 10,000 cases. Since May 2, it has surpassed the number of cumulative cases reported from China at that period, reaching 85,380. The number of cases continued to rise in the period of May to July, until reached to a peak of 69,074 cases daily on July 31. After that the number kept on declining slightly until early of Nov., and then rose again. By Dec. 18, the daily number of new cases reached a peak of 70,574 for the year. The curves of daily deaths and cumulative deaths in Brazil were similar to the curves of daily new cases and cumulative cases, respectively. According to the present trends, in general, the second epidemic peak of the COVID-19 in Brazil will appear within the next two months. It is likely to become the third country with cumulative number of more than 10 M cases. Figure 2A shows the incidence rates of COVID-19 in other major countries. Russia's COVID-19 epidemic developed slowly before March. However, since April, the epidemic has developed relatively fast, reaching a level of more than 10,000 cases per day in early May, and the cumulative deaths were increasing rapidly, resulting in high a case fatality rate [18] . These trends appeared to be slowing down between June and Oct. But after Oct. 4, a trend of increasing by 10,000 cases every day appeared again. By Dec. 21, it reached the level of 29,350 cases a day, becoming the fourth country in the world in terms of cumulative cases in 2020, and the epidemic trend is not optimistic at present.
The epidemic of COVID-19 in France grew at a relatively rapid rate from early March to April. However, it experienced a relatively slow plateau from May to Aug. The increase in case numbers between Sept. and Nov. was relatively fast, reaching a high level [19] . The prevalence of COVID-19 in the UK was roughly the same as that in France from early March to April, but soon surpassed France, mainly because of the delayed "social distancing" policy, or the prevailing concept of "herd immunity" [20] seen in some European countries. After mid-Sept., the number of cumulative cases surpassed by that of France, but at a still faster rate. The UK has become the sixth most prevalent country in the world. Italy is one of the European countries where the COVID-19 epidemic occurred earliest (March). The increase in case numbers before May was relatively rapid. The epidemic was relatively stable from June to Sept., and increased from Sept. to Oct. After Oct. 17, it accelerated sharply again, with the number of new cases on Nov. 14 being 40,902. After Dec. 11, the total number of cases ranked seventh in the world.
Spain was not an early epidemic country in Europe. The initial epidemic situation of COVID-19 was similar to Italy [21] , but after March it rapidly became the country with the most severe disease in the European countries. It was relatively stable after mid-May, and accelerated again from July to Oct., becoming the country second only to the incidence of Russia. It was surpassed by France in late Oct. and by Italy and the UK after Dec. 6, ranking eighth in the world. The COVID-19 epidemic at the initial period in Germany was similar to that in France [21] . Before Aug., it was similar to that of France but slightly higher than that of the UK. After Aug. 27, it was overtaken by France again, and the subsequent epidemic trend was similar to Italy but the number of cases was lower. The increase in the daily number of new cases and the cumulative case accelerated after later Oct., indicating that its incidence peak has arrived. At the end of 2020 it ranked 9th in the world. Colombia is a country in South America with a high incidence second only to Brazil, but its outbreak started late. After the cases appeared in March, they showed a pulse-like onset, and a steady lower trend observed in early May [22] . The number of cumulative cases rose rapidly after July, surpassing France, Germany, Italy, the UK, and Spain. It was surpassed by Spain and France in late Oct., by the UK in early Nov., by Italy in mid-Nov. and by Germany in mid-Dec. Colombia ranked 10th globally in the total number of COVID-19 cases in 2020.
The above data analysis shows that for COVID-19 the increments of cumulative growth from 100 cases, to 1,000 cases, to 10,000 cases and to 100,000 cases, in the absence of effective control mechanisms and policies, are about ten days for each 10-fold increase in magnitude. If there were quarantine measures, namely, intervention or exercising social distancing mandatese, the time of growth of this magnitude would be lengthen; if there were no control measures, the time to 10-fold increase in magnitude would be signi cantly shorter. For example, in the early stage of China's epidemic development, as the cumulative number of cases was less than 1,000 (before Jan. 25), the 10-fold increase in magnitude was very short; after strengthening prevention and control, then the time of case increase from 1,000 cases to 10,000 cases became longer; and so far there were no more than 100,000 of cumulative cases in China. In contrast, in countries with no containment measures of prevention and control, such as in the US, the time of 10-fold increment from 100 cases to 1,000 cases, to 10,000 cases, and to 100,000 cases, were less than 10 days! This may re ect the COVID-19 epidemic severity and regularity under the "natural condition", and the basic reproduction numbers [21] . On the other hand, it told us that the effective prevention and intervention can contain the epidemic; and China's prevention and control measures for the COVID-19 were prompt and reasonable [3] .
An important indicator for assessing the severity of an epidemic is the cumulative number of deaths.
However, the number of cumulative deaths will be affected by the number of cumulative cases, and by the size of the country's population. Therefore, while caring about the total number of cumulative cases and cumulative deaths in a de ned period, we must mention the case fatality rate that is the ratio of cumulative deaths to cumulative number of cases; and also we must care about the incidence and mortality rates which are based on the national or regional population size. General speaking, the case fatality re ects how many people (cases) die of the disease from patients (the denominator is the sick) [23] , demonstrating the hazard degree of disease to life. In the epidemiological sense, the incidence (mortality) rate is concerned about how many patients have suffered or died of the disease in the population (the denominator is the total population), re ecting the epidemic (death) degree or range of a disease. Assume that 200 cases are from a 1 M population and 8 died, making incidence rate of 20 per 100,000 (200/1 M), mortality rate of 0.8 per 100,000 (8/1 M), and the case fatality of 4% (8/200), telling us, obviously, the different implications clinically and epidemiologically.
COVID-19 incidence, mortality, and fatality rates are calculated based on the WHO data and the population data by country. The results show that in the year of 2020, the Top 30 countries with the largest number of cumulative cases account for more than 1/2 (50.38%) of the global population, but the cumulative cases account for 85.70%, and the cumulative death cases account for 88.18% of the global total deaths of COVID-19. The incidence rate and mortality rate of Top 30 countries were 1827.17/10 5 and 41.45/10 5 , respectively, being higher than the total incidence rate and mortality rate of 1074.13/10 5 and 23.70/10 5 all over the world. The US with high number of cumulative cases surely had high an incidence rate, but was not the country with the highest incidence rate. Its incidence and mortality rates were 1,023.60/10 5 and 41.33/10 5 , respectively, ranking 6th and 14th, respectively, in the world. Table 1 shows that although the number of cumulative cases in Czechia is listed as only 21st, the incidence rate of 6,763.71/10 5 was the highest among the Top 30 countries, due to its small population of less than 1 M. In fact, when considering the incidence rates of COVID-19 from all countries in the world, we would nd that many so-called small countries (territories or regions) were also on the list. Figure 3A shows that the highest incidence rate of COVID-19 is found to be in Andorra (10,373.86/10 5 ), followed by Luxembourg (7,861.99/10 5 ), and Montenegro (7,615.79/10 5 ), although their cumulative cases are not listed in the TOP 30 countries.
The cumulative cases (96,673) and cumulative deaths (4,788) in China were ranked at the 79th and 43rd, respectively, but the incidence rate (0.33/10 5 ) and mortality rate (0.33/10 5 ) ranked only 207th and 188th, respectively, simply because of its huge population but relative fewer cases (deaths). Based on this situation, although the COVID-19 had the rst break out in China in the rst quarter of the year 2020, it was also the rst to be controlled in the world, due to its rapid, appropriate and effective measures [3,4,10] . It has set a convincing example for global prevention and control of this pandemic.
Fatality is an important indicator of disease control management, medical treatment and prognosis. For that of COVID-19, someone [24,25] argued the way of calculation because of the estimation of the denominator, but in this paper, that would be no real impact on estimation of the rate. The overall case fatality rate of COVID-19 in 2020 was 2.21%; while the rate in the Top 30 countries was slightly higher than the global level, being 2.27%. There were no real distinction for fatality rates of COVID-19 between the developed and less developed countries, as shown in Fig. 3C. This may be related to the fact that COVID-19 is an emerging disease, and its clinical outcome not only depends on the clinical treatment itself, but depends on many factors such as the extent of the epidemic in each country, emergency treatments, the availability of medical resources and others [8,10] . In China, for instance, which was the rst to bear the brunt of the outbreak, exhibited a fatality rate that gradually increased from about 2% at the beginning to 5.52% at the peak on April 17, and then steadily decreased with an average rate of 4  Fig. 1B that the high fatality rate in May in the US may be related to the rst outbreak peak in April, and may be also related to the failure of patients to receive possible emergency treatment due to the crowding out of medical resources [23] . In Europe, the fatality rate was very high in the early outbreak countries, as was it high in early period in China [26] . In France, for example, it was reported that in the rst three months of the epidemic, due to lack of validated COVID-19 treatment, the fatality rate in some medical institutions reached up to 44% [27] .
Why with so many countries facing the outbreaks of COVID-19, were there big differences in incidence, mortality, and fatality? The answer is likely involve many factors [5,8,10, 23,26,28−31 ] : 1) In countries with earlier outbreaks, due to lack of knowledge, of prevention and control measures, the epidemic developed rapidly; 2) Because the novel coronavirus was not recognized initially by the symptoms, development or prognosis [5,28] , the clinicians faced to the shortage of medical treatment, to the crowding of medical equipment [23] ; 3) Due to the relatively high proportion of an aging population [32] , such as in Europe and America, elderly people were more easily infected with the coronavirus and to die from the disease; 4) Because there was no proven drug treatment, fatality from COVID-19 was not essentially different between large and small countries, between developed and less developed countries. 5) Personal selfprotection (mask wearing and hand washing), community isolation, and social distance are important factors and even decisive factors affecting the disease epidemic [10] , although a report showed no signi cant bene ts on case growth of more restrictive non-pharmaceutical interventions [33] .
The length of time that the number of cases doubled may be one of the important and sensitive indicators to evaluate whether the disease is effectively controlled or not. Due to the diversity of the global society and the complexity of social systems, and the cultural differences in the cognition of diseases, individual behavior will be crucial to control the spread of COVID-19. Personal behavior, rather than government action, in western democracies might be the most important issue. Early self-isolation, and social distancing are key. Government actions to ban mass gatherings [10] would be essentially important.
According to the current epidemic situation and trends, the global burden of COVID-19 is not slowing down. So far the initial, novel coronavirus vaccines in the world have achieved good results in early trials, and the current COVID-19 vaccine candidates are safe, tolerated, and immunogenic [34] , but their shorter or long term e cacy or the extent of protective effect need to be veri ed in different populations [35] . Dissemination to all people of the global community remains an enormous challenge. Therefore, strict isolation, social distance, even lockdowns may be still the best vaccine [36] before effective virus vaccine immunization With the vaccines can be broadly administered.
From the analysis of this paper, it is evident that COVID-19 will be still on the rise in the US for months to come. If the current prevention and control measures and capabilities can't be effectively changed (if the effect of the vaccine is uncertain), it may reach at least the level of 50 M cumulative cases in the year 2021. Assuming its low case fatality rate of 1.6% is sustained despite the emergence of more infectious variants, the number of cumulative deaths due to COVID-19 will reach to 800,000. For India, if new peak of outbreak does appear, its number of cumulative cases will be contained within 40 M, with a number of cumulative deaths of over 500,000. While the number of new cases in Brazil, if no second peak wave in 2021, the cumulative number of cases may rise to 30 M. Its cumulative number of deaths may reach to 700,000, due to its relatively high case fatality rate. The numbers of cumulative cases from only these 3 countries will exceed 120 M, that will be far over some estimation of 80 M in 2021 worldwide [37] . From a global perspective, countries and regions where epidemic prevention measures were in place, community isolation, public health supervision, and government regulation were better, the epidemic trends could be seen to have slowed down [8,10,19] . For the past hard year, China's local prevention and control has undoubtedly handed in excellent answers [3,4] , but at present, it still needs to be vigilant and prevent imported cases.
To curb the COVID-19 pandemic worldwide, the prevention and control efforts from public professionals, treatment capacity from medical workers, development capacity from biotechnological researchers, and the attitude and measures of various countries' governments, and the public's awareness, cooperation in self protection, and the overall effectiveness of the vaccination programs [31][32][33][34][35][36]38] will be the important factors to decide whether the COVID-19 will continue to be epidemic or become contained. COVID-19 control would be possible only if the whole society embraces the challenges, and learned more from failure in prevention [39] . But, there is a long way to go.   Incidence rates, mortality rates and fatality rates of COVID-19 in Top 30 countries in 2020 A. Incidence rates; B. Mortality rates; C. Fatality rates.