Thailand provides free COVID-19 testing for citizens. Photo: REUTERS
COVID-19 has caused four global waves of the pandemic, with each wave dominated by a specific variant. With thousands of variants recorded, scientists are facing immense pressure in analyzing these strains and preparing response scenarios as the virus continues to evolve with increasing complexity.
A virus capable of causing a global pandemic must be easily transmissible from person to person. In its early stages, the SARS-CoV-2 virus causing COVID-19 was confirmed to spread slowly, primarily through droplets, close contact, or indirectly via surfaces. To trigger a pandemic, the virus needed to mutate sufficiently to spread easily among people in the broader community and transmit during the asymptomatic phase—traits that have made SARS-CoV-2 far more dangerously transmissible than it was initially.
Existing variants of this viral species include: the B.1.1.7 (Alpha) strain, first detected in the UK and subsequently spreading globally; it remains one of the most prevalent strains, though it is gradually being superseded by the emergence of the Delta variant. The B.1.351 (Beta) strain, detected in South Africa in December 2020, is believed to reduce vaccine protective efficacy. The P.1 (Gamma) strain, detected in early January this year in Brazil, circulates strongly and evades the neutralizing effects of older-generation vaccines. The B.1.617.2 (Delta) strain, detected in India in late 2020, rapidly became dominant, spread globally, and threatened to reverse anti-epidemic efforts in many countries; this strain currently accounts for the vast majority of infections in Viet Nam. The C.37 (Lambda) strain, detected in December 2020 in Peru, accounted for up to 82% of new cases there and spread to approximately 24 countries, predominantly in South America. Over the past two months, this strain has spread rapidly and has been flagged by the World Health Organization (WHO) as a variant of concern.
An increase in transmission speed does not necessarily mean the disease is more severe. Currently, vaccines appear to have a slightly reduced capacity to prevent viral transmission, but their protection against severe illness and hospitalization remains robust. Nevertheless, when these variants emerge, they rapidly become dominant and displace other strains. Surging case numbers overwhelm healthcare systems and indirectly lead to increased mortality rates.
Like other RNA viruses, SARS-CoV-2 lacks an error-correction mechanism during replication. Consequently, approximately every 1,000 replications, an error occurs in the virus's genetic code. If this error is functionally significant, it generates a new viral version; if the mutation confers enhanced transmissibility, it will rapidly spread and replace the older version, forming a new variant.
The proliferation of new variants requires scientists to carefully study them to improve our understanding and detect emerging strains early. A new variant must be evaluated to determine: whether it transmits more easily; whether it causes milder or more severe disease; whether it can be detected by current diagnostic tests; how it responds to existing treatments; and whether it alters vaccine protective efficacy. In Japan, viral sequencing tests are performed routinely, and reports on viral evolution are published weekly for early warning purposes.
Countries with poor epidemic containment serve as fertile ground for viral variants, providing opportunities for the virus to mutate and generate more sophisticated strains. This is why a series of countries faced travel bans to and from their territories after variants were reported there, such as the UK, South Africa, Brazil, and India. However, these entry restrictions are often implemented too late, after new variants have already infiltrated destination countries. This underscores why the global community must join hands to control the epidemic, as no nation is isolated from the virus. Viet Nam was praised by the world for a prolonged period precisely because of its decisive actions to contain the epidemic.
Several other countries and territories have also been commended, including Taiwan (China) with its effective quarantine and contact tracing strategy; Singapore with its smart management system, contact tracing, and vaccination; South Korea with mass testing, contact tracing, and case monitoring; New Zealand with quarantine management and high-risk zone lockdowns; and Australia with targeted short-term lockdowns and closures.
Recently, many have recalled the Severe Acute Respiratory Syndrome (SARS) epidemic that swept the globe in 2003 and MERS in 2012. Although controlled and eradicated, they clearly demonstrated that coronaviruses mutate and possess the capacity to transmit easily between humans. SARS-CoV-2 became a pandemic virus primarily because it is highly unpredictable. A routine practice during epidemic waves is tracking the genetic evolution of the virus using gene sequencing methods. Based on current results, it is very difficult to predict when this virus will transition into a seasonal flu-like endemic virus that humanity can live alongside. Until this occurs (i.e., the virus becoming milder), we must exhaust all our capabilities to contain it.
Some foreign commentators have suggested that the emergence of the Delta variant would spell the end of Viet Nam's good fortune. In reality, claiming that Viet Nam was merely fortunate in previous epidemic waves is entirely inaccurate. Achieving these successes required the Party, State, and Government to intervene promptly and decisively, with strong commitments to epidemic readiness. The Ministry of Health, relevant ministries, departments, and local authorities are currently deploying numerous measures to respond to the outbreak. When the outbreak occurred, decisive measures were enacted, such as establishing unified central contact-tracing teams operating alongside tens of thousands of contact tracers at all levels nationwide.
Furthermore, the most distinctive feature has been the active participation of Community COVID-19 Safety Teams. Comprising tens of thousands of teams, they serve as the grassroots extension of the epidemic prevention and control forces, enabling the earliest possible detection of imported cases and symptomatic individuals within the community for targeted interventions.
Alongside enhanced community surveillance, testing-based surveillance is indispensable. Continuous monitoring and detection of new variants have also been assigned to research institutes, ensuring that any significant viral introduction or notable mutation is controlled and monitored, thereby making a vital contribution to the overall success of Viet Nam's viral containment strategy.
Dr. Pham Quang Thai
Source: https://nhandan.vn/tin-tuc-y-te/sars-cov-2-bien-chung-nguy-co-toan-cau-va-kinh-nghiem-doi-voi-viet-nam-655809/?fbclid=IwAR3trd2y5FvUP92iQ4Yn6XgEWTJNCH6l1a6Xabhqy2NhKXZ1ehJlh4jje5E