The History and Epidemiology of SARS-CoV-2: Tracing the Origins and Spread
The Emergence of SARS-CoV-2: From Wuhan to Global Pandemic
In late 2019, an enigmatic ailment characterized by symptoms akin to lung fibrosis and pneumonia gained prominence in Wuhan, China, drawing the attention of health experts worldwide (Zhou et al., 2020). Swift and decisive measures were implemented by the Chinese government to quell the abrupt epidemic outbreak. Designated as the 2019 novel coronavirus (2019-nCoV) on January 12, 2020, by the World Health Organization (WHO), it was classified as an international concern just 18 days later (Coelho et al., 2020). Subsequently, on January 30, 2020, the International Committee on Taxonomy of Viruses christened the virus Severe Acute Respiratory Syndrome 2, or SARS-CoV-2 (Sun et al., 2020). The global impact of this outbreak exceeded the scope of the 2002 SARS outbreak, swiftly transforming into a pandemic facilitated by international travel. The ramifications were catastrophic, with a staggering death toll of 5.31 million worldwide and far-reaching economic consequences.
Exploring Coronaviruses in the 21st Century:
Unveiling the Novelty of SARS-CoV-2 and its Viral Architecture
The 21st century has witnessed a surge in coronavirus research, with each encounter revealing novel facets. Resolving these intricacies involved genetic sequencing, and preceding SARS and Middle East respiratory syndrome (MERS), as the most recent examples (Gorbalenya et al., 2020). A positive-stranded RNA virus, ranging from 26-32 kb, SARS-CoV-2 boasts a diameter of 60-140 nm, exhibiting distinctive crown-like spike proteins when observed under an electron microscope (Madabhavi, Sakar & Kadakol, 2020). These spike proteins dictate cell tropism, enabling virus-cell binding and penetration (Coelho et al., 2020). The interaction between SARS-CoV-2 and the angiotensin-converting enzyme 2 (ACE-2) receptor in healthy human lung tissue triggers a cascade of alveolar cell injuries and systemic reactions, often leading to severe outcomes (Coelho et al., 2020).
SARS-CoV-2’s Evolution and Classification:
From Zoonotic Origins to Emerging Variants
Belonging to the β-coronavirus cluster, SARS-CoV-2 is the third zoonotic coronavirus disease identified after SARS and MERS. The name stems from its resemblance to two bat-derived SARS-like coronaviruses and a close 50% similarity to MERS (Sachdeva, Kumar & Mohanty, 2021). Its genesis has been linked to the Huanan Seafood Wholesale Market, with evidence suggesting potential human-to-human transmission. SARS-CoV-2’s genome encompasses ten open reading frames (ORFs), with ORF 1a/b constituting approximately two-thirds of the viral RNA, eventually translated into polyproteins. These polyproteins transform into sixteen non-structured proteins, constituting the viral replicase transcriptase complex (Li et al., 2020). Further translation occurs within the rough endoplasmic reticulum (RER), facilitating transcription and viral replication. Another ORF, comprising one-third of the viral RNA, encodes structural proteins, including nucleocapsid (N), spike (S), envelope, and membrane protein (M), without involvement in viral replication.
Evolving Variants and Their Global Impact:
Navigating Through SARS-CoV-2’s Mutation Landscape
The SARS-CoV-2 journey gave rise to several variants, with Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2) emerging due to their enhanced infectivity. In November 2021, a new variant known as Omicron (B.1.1.529) surfaced, boasting a mutation count six times that of the Delta variant, carrying heightened risks and a rapid global spread (Chen et al., 2021).
From Wuhan to Global Spread: SARS-CoV-2’s Unprecedented Expansion
Originating in Wuhan, China, the SARS-CoV-2 outbreak engulfed over 100 countries within a span of 2 to 3 months (Srivastava, 2019). The initial ‘patient zero,’ a female shrimp vendor, managed to recover after a month of treatment (Madabhavi, Sakar & Kadakol, 2020). With all age groups susceptible to infection, the virus spreads through oral, nasal, and ocular routes, primarily transmitted through symptomatic individuals via sneezing or coughing, traveling up to 1 to 2 meters and settling on surfaces. Asymptomatic transmission is also possible prior to symptom onset (Madabhavi, Sakar & Kadakol, 2020). Nasal cavity viral load elevation correlates with severe illness, and individuals remain contagious even during recovery (Zhou et al., 2020).
Survival and Dissemination:
Viability on Surfaces and Incubation Period of SARS-CoV-2
SARS-CoV-2 can survive on surfaces for days in conducive environments, though practices like disinfection and cleaning render them inert. Human incubation periods range from two to fourteen days. By December 15, 2021, Malaysia recorded 2,696,948 COVID-19 cases, leading to 30,989 fatalities, as per the Ministry of Health Malaysia’s report (2021). The first Malaysian case emerged on January 25, 2020, involving three Chinese nationals entering from Singapore (Borneo Post Online, 2020; New Straits Times, 2020).
Tracing the Initial Cases and Subsequent Transmission
Following the first Malaysian case, a 41-year-old male returning from Singapore exhibited symptoms such as fever and cough (Bernama, 2020a). The first local transmission was his younger sister, presenting symptoms of sore throat, cough, and fever (Bernama, 2020b). A dramatic surge in cases was observed after a religious gathering involving 16,000 attendees from across Malaysia, resulting in an exponential rise in infections. Among them, a 34-year-old man attending the gathering succumbed to COVID-19-related complications (Elengoe, 2020).
The trajectory of SARS-CoV-2’s history and epidemiology paints a vivid picture of its origins, rapid global spread, and evolving variants. Understanding these dynamics remains essential in the ongoing efforts to mitigate its impact and prevent future pandemics.