Journal of Preventive Medicine

Keywords

COVID-19, Coronavirus, SARS-CoV-2 spread

Abbreviations

Coronavirus Disease of 2019 (COVID-19), Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), World Health Organization (WHO)

Introduction

In December 2019, a few cases of pneumonia-related illness were reported in Wuhan district of Hubei province in China, all were related to Huanan Seafood Market. The causative agent of this idiopathic atypical idiopathic pneumonia was identified [1]. It was found to be caused by a new virus, closely related to the previously identified members of the Coronavirus family. At first, it was named novel Coronavirus (nCoV-19). Afterward, the International Committee on Taxonomy of Viruses (ICTV) named it SARS-COV-2 based on phylogenetics and taxonomy, as the genetic sequence of nCoV-19 was closely related to SARS coronavirus [2].

The origin of novel coronavirus is still unclear. Some evidence suggested that it spread via animals, i.e., bat, thus nCoV is a zoonotic virus, and just like SARS and MERS, this epidemic is also a spillover by an animal virus [3]. Bat coronavirus genome (BatCoV RaTG13), present in Rhinolophus affinis bat, showed 96.2% resemblance with SARS COV-2 that pointed towards the possible origin of SARS COV-2 from Rhinolophus affinis bat [4]. Later, the World Health Organization declared COVID-19, an epidemic [5]. After separating viral components, diagnostic kits and RT-PCR techniques were developed to aid the detection of viral infection.

In the suspected cases. Previously, CT scans and thermal screening methods were being used [6]. Significant symptoms included fever, shortness of breath, dry cough, fatigue, and flulike symptoms, etc. Various studies showed that the incubation period ranged from 1 to 14 days (mean incubation period 5-6 days). The case reproduction number of nCoV-19 is higher as compared to the other coronavirus epidemics [7].

Soon, from Wuhan, it was spread to other regions in China and then globally. Thus, this epidemic was named Coronavirus Disease of 2019 or COVID-19. In January 2020, the WHO declared the COVID-19 public health emergency of international concern [8]. In March 2020, WHO launched a "Solidarity Trial" program – A global collaboration to develop a safe and effective vaccine against SARS-CoV-2 [9]. It was found to be transmitted by respiratory droplets and human contact. Currently, there is no specific treatment and vaccine against SARS COV-2. It uses the angiotensin-converting enzyme 2 (ACE2) to enter the host’s cells [10]. For prevention of COVID-19 spread, social distancing, and avoiding contact with SARS-CoV-2 with the help of masks and gloves was recommended. Lockdown and isolation immediately ensued in most of the countries of the world [11].

COVID-19 reached globally via community spread. Air travels and cross-country travels were banned from hampering this epidemic. Airport screening was being carried out, and the suspected cases were kept in quarantine [12]. Despite all these steps, the global spread of COVID-19 was very rapid. Till now, 205 countries in the world are affected by COVID-19. 6,748,525 total cases, 394,368 deaths worldwide, and the number of recovered patients is 3,277,374 [13]. These statistics show that the case mortality rate of COVID-19 is less than that of other coronavirus epidemics, MERS (2012), and SARS (2003), but it is more contagious than these two [14]. 98% of the affected cases developed mild symptoms, while only 2% showed a severe form of the disease, i.e., lung fibrosis, end-organ failure leading to the individual's death. Various studies showed that old age group and patients with chronic conditions like chronic obstructive pulmonary disease, cardiovascular illness, metastasis, immunocompromised state, organ failure, and smokers, etc. are particularly vulnerable to severe COVID symptoms, while young, healthy and immunocompetent individuals mostly develop mild symptoms and certain asymptomatic laboratory-confirmed cases have also been reported [12, 15]. An assessment of COVID patients showed that the approximate time from onset to clinical recovery for mild cases is two weeks, while critical patients recovered in about 3-6 weeks [16]. On the community level, complete lockdown and closure of institutes, offices, industries, and commercial areas had several effects. Millions of the masses were unemployed; the economy collapsed, several sectors, eg. The oil industry crashed [17]; people living in their homes suffered from psychological symptoms like fear, anxiety, stress, and depression, i.e., Psychological implications of COVID-19 [18]. The WHO published guidelines for effective prevention of the disease like contact-free work facilities such as online commerce, e-learning, social distancing, transport restrictions, quarantine measures, personal protective habits like frequent hand washing and cough etiquette [19].

Origin

In the last months of the year 2019, a few cases of pneumoniarelated illness were reported in the vicinity of Wuhan. The clinical characteristics of this pneumonia-like illness closely resembled with viral pneumonia. Those patients were investigated for the causative agent of this illness. It was found not to be caused by previously known general pneumonia-causing viruses. On December 31, 2019, Chinese officials reported the WHO country office dealing with idiopathic pneumonia. Out of 44 cases of this unknown illness, nearly all belonged to Huanan Seafood that dealt with seafood and lived animal trade [20]. Laboratory analysis and sequencing of the causative virus showed that it is a new virus that had not caused any illness in humans before now [21]. Due to the impending risk of the Coronavirus epidemic spread, the market was immediately closed on January 1, 2020 [20].

Moreover, it closely resembles with bat coronavirus. So, it is unknown yet, how this bat coronavirus began to infect humans [3]. Further cases of such illness were reported afterward that were not related to the Huanan Seafood market, which strongly suggested that the bat virus was transmitted from the affected cases. Human to human transmission was further established [22]. Mass transportation in the last week of December 2019 (Chinese New Year) led to the rapid spread of Coronavirus disease. From Hubei Province, the Coronavirus epidemic spread to other parts of China, i.e., Hongkong, Shanghai, Beijing, and so on. COVID-19 soon spread to Thailand, the USA, Taiwan, and so on. On January 25, 2020, a complete lockdown was ordered in Wuhan [23].

Transmission

Earlier in the course of the COVID-19 pandemic, the modes of disease transmission were ambiguous. During the identification of the causative agent yet before the transmission of SARS-COV-2 could be established, community spread of the disease is likely to have happened before effective measures could be taken [24]. The WHO stated four levels of COVID-19 transmission [25]. These are territories or local areas with:

1. No cases reported

2. Sporadic cases.

3. Clusters of cases

4. Community transmission.

There are two common routes of transmission of SARS-COV-2 viz Direct transmission (viral transfer through coughing, sneezing, and respiratory droplet inhalation transmission) and Contact transmission (viral contact with mouth, nose, eye or mucous membranes) [10]. Studies show that the clinical characteristics of COVID-19 mainly affect the respiratory tract, but the conjunctival swabs of confirmed and suspected COVID cases suggest that the SARS-COV-2 transmission can also occur through viral contact to the eyes [26]. Surprisingly, a patient of SARS-COV-2 infection in Germany contracted the virus from an asymptomatic patient or carrier, which shows that viral transmission may take place through contact with asymptomatic patients [27].

Discussion

COVID-19 originated as a zoonotic illness though the exact origin is not confirmed yet. As the primary site of origin is Huanan Seafood Market that deals in seafood and live animal trade, and the gene sequencing of nCoV- 19 showed remarkable resemblance with bat coronavirus, so it supports the zoonotic origin of SARS-COV-2.

The WHO and health authorities mobilized health units and policies to contain the epidemic. The WHO Situation Reports elaborated certain aspects of COVID-19 epidemic emphasizing on halting the spread of disease. These comprised of the technical details for the healthcare teams and guidelines about detection, management, and tentative treatment of the affected cases. The WHO established IMST (Incident Management Support Team) to control the epidemic and published guidelines about contact & droplet transmission and aerosol-generating medical therapies. Travel restrictions, social distancing, and a ban on public gatherings ensued.

Despite all these steps, COVID-19 reached to all continents except Antarctica in just three months after COVID- 19 onset (Table 1). Dominant factors leading to violent spread are earlier inattention to the epidemic, inefficient epidemic control systems, lack of health care expertise in epidemic confinement, and unchecked immigration.

Table 1: Chronological timeline and index cases of COVID-19 in the countries across the world.

Local spread in China soon followed by the spread of disease to neighboring countries. Thailand, being first to be affected by COVID-19 after China. Taiwan, Singapore, Japan, Hongkong, Vietnam, Nepal, and many other.

Asian countries soon reported first COVID cases, all of which were exported cases from neighboring countries, especially China (Table 1). The epidemic surge in Italy was rapid, and soon it became the hub of COVID-19 spread to the nearby territories. Denmark, Germany, Croatia, Austria, Israel, Nigeria, Canary Islands, Spain, France, Netherlands, Derbyshire, and Wales reported their first cases with exposure to Italy. Iran, Italy, and the US, as hotspots to COVID-19, contributed to the global spread of COVID-19. Iraq, Syria, United Arab Emirates, Dubai, Canada, Lebanon, Turkey, and Azerbaijan had COVID-19 epidemic onset tied to Iran [Table 1]. A study shows the effect of air travel to and from Iran caused International COVID-19 spread to countries like Lebanon, Canada, and the United Arab Emirates despite their low Infectious Disease Vulnerability Index (IDVI) scores [29]. International Air and ground travel continued the dissemination of exported cases across the globe.

Travel restrictions proved to be a useful step in containing the COVID-19 pandemic. Various community gatherings, trade expos, international seminars, tourism, and community activities like funerals, wedding ceremonies were banned in compliance with the guidelines of the World Health Organization. Most of the countries showed serious concern about the pandemic. Vigorous steps like complete lockdown were observed in most of the countries of the world. Most countries responded effectively, against COVID-19 threat and optimized their healthcare facilities. In China, the number of new cases began to decline after a steep rise in the Epidemiological curve due to efficacious confinement of local transmission and proper management of the existing cases.

Conclusion

COVID-19 is a public health emergency of international concern, affecting almost 211 countries of the world, and it is probably the biggest pandemic in the last 50 years. More than 6,748,525 cases and 394,368 deaths worldwide. As compared to the other Coronaviruses (SARS and MERS), there are more people affected by COVID-19. Transmission of the virus to countries and regions led to a “coronavirus crisis.” Mass transport and International travel resulted in rapid COVID-19 spread. Due to the variation in healthcare resources and epidemic control designs, many countries in the world are suffering from an enormous burden of the disease.

Global integration and coordination are required to dampen the flow of the disease. Effective immigration strategies, global aid, greater adherence to the WHO guidelines, and health policies are the key measures that can help in flattening of the epidemiological curve, and effective control of COVID-19.

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