key: cord-0834524-trmspx1y
authors: Zhou, Chuan-Min; Qin, Xiang-Rong; Yan, Li-Na; Jiang, Yuan; Ke, Heng-Ning; Yu, Xue-Jie
title: Global trends in COVID-19
date: 2022-03-04
journal: Infectious Medicine
DOI: 10.1016/j.imj.2021.08.001
sha: 2e93b70d5190555d85af90e14f9e497082c91452
doc_id: 834524
cord_uid: trmspx1y

The pandemic COVID-19 is certainly one of the most severe infectious diseases in human history. In the last two years, the COVID-19 pandemic has caused over 418.6 million confirmed cases and 5.8 million deaths worldwide. Young people make up the majority of all infected COVID-19 cases, but the mortality rate is relatively low compared to older age groups. Currently, about 55.04% individuals have been fully vaccinated to reach herd immunity globally. The challenge is that new SARS-CoV-2 variants with potential to evade immunity from natural infection or vaccine continue to emerge. Breakthrough infections have occurred in both SARS-CoV-2 naturally infected and vaccinated individuals, but breakthrough infections tended to exhibit mild or asymptomatic symptoms and lower mortality rates. Therefore, immunity from natural infection or vaccination can reduce SARS-CoV-2 pathogenicity, but neither can completely prevent SARS-CoV-2 infection/reinfection. Fortunately, the morbidity and mortality of COVID-19 continue to decline. The 7-day average cumulative case fatality of COVID-19 has decreased from 12.3 % on the February 25, 2020, to 0.27% January 09, 2022, which could be related to a decreased SARS-CoV-2 variant virulence, vaccine immunization, and/or better treatment of patients. In conclusion, elimination of SARS-CoV-2 in the world could be impossible or at least an arduous task with a long way to go. The best strategy to prevent COVID-19 pandemic is to expand inoculation rate of effective vaccines. As the population reaches herd immunity, the mortality rate of COVID-19 may continue to decrease, and COVID-19 could eventually become another common cold.

Coronaviruses are a group of enveloped RNA viruses with unsegmented, positive-stranded RNA genomes that are classified in the order Nidovirales, the family Coronaviridae, and the subfamily Coronavirinae. Based on serological evidence and genomic structures, the subfamily Coronavirinae is subdivided into the four genera Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus. Actually, coronaviruses have been discovered all over the world, accompanying that most of us will be infected by a coronavirus at some point at least once in our lives. In general, coronaviruses cause mild to moderate respiratory and intestinal infections in vertebrates [1] . To date, seven human coronaviruses have been detected with four human coronaviruses causing common cold including OC43 (β-CoV), HKU1 (β-CoV), 229E (α-CoV), and NL63 (α-CoV), and three human coronaviruses causing severe respiratory diseases including severe acute respiratory syndrome coronavirus (SARS-CoV) (β-CoV) [2, 3] , Middle East respiratory syndrome coronavirus (MERS-CoV) (β-CoV) [4] , and SARS-CoV-2 (β-CoV) [5] .

After the first report of COVID-19 cases in late 2019, SARS-CoV-2 spread rapidly around the world. The World Health Organization (WHO) declared COVID-19 as a serious public health emergency of international concern on January 30, 2020, and a pandemic situation on March 11, 2020. To date, the COVID-19 pandemic has wreaked havoc around the world for two years.

Globally, over 418.6 million confirmed COVID-19 cases and 5.8 million deaths have been reported, and that is certainly an undercount because of many lower income areas still lack enough medical resources or vaccines. According to the Global Economic Prospects report, economic growth will slow down under COVID-19 pandemic and is expected to decline markedly from 5.5% in 2021 to 4.1% in 2022, and 3.2% in 2023. We are still trapped in the COVID-19 pandemic. Fortunately, the good news is that, despite the constant appearance of new SARS-CoV-2 variants, the case fatality rate (CFR) of COVID-19 keeps decreasing, which could be associated with the immunization with COVID-19 vaccine globally, the improved medical treatment for COVID-19, and the decrease virulence of SARS-CoV-2 variants, and importantly, that do not mean we quit battling against COVID-19. Proper policies to control and prevention COVID-19 pandemic precisely are still important until the moment comes. However, there is still so much we do not know about SARS-CoV-2, and we still have a long way to go with SARS-CoV-2. More efforts are urgently needed to understand SARS-CoV-2 and control the outbreak of COVID-19. We must face the reality that SARS-CoV-2 could continue to coexist with humans on Earth for a long time.

Reported COVID-19 cases may be just the tip of the iceberg, as more than 80% of people with COVID-19 are asymptomatic or mild, which may go unrecognized and unreported [ 2 ). The high incidence in Europe may be due to the aging of the European population and the high level of diagnosis.

People around the world did not suffer from SARS-CoV-2 before 2019 and are therefore 

Of particular concern are mutations in the spike protein, especially in the spike protein especially for the receptor binding domain (RBD) [29] [30] [31] . The first reported SARS-CoV-2 mutation is D614G in the spike protein [32, 33] , which can interact with ACE2 more efficiently and has potentially high infectivity and viral load in the upper respiratory tract of COVID-19

patients, but does not increase disease severity [32, 33] contagious and may be 2.8 times more contagious than the Delta variant [45] . In addition, the Omicron variant exhibits a higher reproduction number, which could be 7 or even greater [46] , allowing the variant to go unrecognized and easily spread around the world [6]. Second, the Omicron variant prefers to infect the upper respiratory tract and shows lower virulence, resulted in no more severe illness then reported SARS-CoV-2 variants [47, 48] . Third, the Omicron variant was able to evade the immune system defenses and resist nAbs in people who had previously been vaccinated or infected with SARS-CoV-2, causing more frequent breakthrough infections than previous variants in recent months [49] [50] [51] [52] [53] [54] [55] . In addition, the variant was resistant to a therapeutic monoclonal antibody [56, 57] . Notably, it was predicted that the vaccine-escape capability is about 14 times more efficient than the Delta variant and has an 88% chance to escape current vaccines [45] .

Actually, the cause of SARS-CoV-2 breakthrough infections can be divided into two parts.

On one hand, lower nAb levels may increase the risk of breakthrough infections. On the other hand, the emergence of novel SARS-CoV-2 variants could induce immune escape and promote the risk of breakthrough infections. Breakthrough infections continue to be a major public health concern, raising concerns about vaccine hesitancy and anxiety. The good news is that while the Although most genomic alterations of the SARS-CoV-2 genome were synonymous, we cannot deny that some mutations may affect virulence. Despite the robust increase of COVID-19 cases since mid-December 2021, the COVID-19 deaths and CFR keeps decreasing (Figure 5 and 6) .

The cumulative CFR and 7-day average CFR of COVID-19 has decreased from 6.89% on the HCoV-HKU1, as the population reaches herd immunity worldwide, the mortality rate of SARS-CoV-2 will continue to decrease [61,62].

The truth is that we are still trapped in the COVID-19 pandemic phase. However, a vaccine with a short duration of protection will make it difficult to eliminate SARS-CoV-2.

Additionally, many animal populations are also susceptible to SARS-CoV-2, such as ferrets, Large information about SARS-CoV-2 remains elusive. We do not know whether vaccines could halt the spread of SARS-CoV-2 in a short time or whether SARS-CoV-2 will be eradicated worldwide. It is difficult to predict whether SARS-CoV-2 will be an endemic virus similar to influenza, but it may pose less of a threat over time. It seems impossible to completely control the spread of COVID in the short term. Hopefully, the mortality rate of COVID-19 may continue to decrease and COVID-19 will be eradicated or reduced in some countries through herd immunity if enough people are vaccinated within a year or two. Stringent preventive measures cannot be neglected before the outbreak of COVID -19 is contained.

Author Contributions: Conceptualization, X-jY. Original draft preparation, C-mZ, X-rQ, L-nY, and Y-jJ Writing-review and editing, H-nK and X-jY. Project administration, X-jY.

Funding acquisition, X-jY. All authors contributed to the article and approved the submitted 

☐ ×The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

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