Like the SARS-related coronavirus implicated in the 2003 SARS outbreak, SARS‑CoV‑2 is a member of the subgenus Sarbecovirus (beta-CoV lineage B). Coronaviruses undergo frequent recombination. The mechanism of recombination in unsegmented RNA viruses such as SARS-CoV-2 is generally by copy-choice replication, in which gene material switches from one RNA template molecule to another during replication. The SARS-CoV-2 RNA sequence is approximately 30,000 bases in length, relatively long for a coronavirus—which in turn carry the largest genomes among all RNA families. Its genome consists nearly entirely of protein-coding sequences, a trait shared with other coronaviruses. (Full article)
COVID-19 is mainly transmitted when people breathe in air contaminated by droplets/aerosols and small airborne particles containing the virus. Infected people exhale those particles as they breathe, talk, cough, sneeze, or sing. Transmission is more likely the more physically close people are. However, infection can occur over longer distances, particularly indoors.
The number of people generally infected by one infected person varies, but it is estimated that the R0 ("R nought" or "R zero") number is around 2.5. The disease often spreads in clusters, where infections can be traced back to an index case or geographical location. Often in these instances, superspreading events occur, where many people are infected by one person. (Full article)
Goals of mitigation include delaying and reducing peak burden on healthcare (flattening the curve) and lessening overall cases and health impact.
Many countries attempted to slow or stop the spread of COVID-19 by recommending, mandating or prohibiting behaviour changes, while others relied primarily on providing information. Measures ranged from public advisories to stringent lockdowns. Outbreak control strategies are divided into elimination and mitigation.
Experts differentiate between" zero-COVID", which is an elimination strategy, and mitigation strategies that attempt to lessen the effects of the virus on society, but which still tolerate some level of transmission within the community. Containment strategies consists of the use of public health measures such as contact tracing, mass testing, border quarantine, lockdowns and mitigation software.These strategies can be pursued sequentially or simultaneously during the acquired immunity phase through natural and vaccine-induced immunity.
Hundreds of protesters clash with police in Shanghai as security forces attempt to disperse the crowds during a candlelight vigil for the victims of the fire on 24 November in Ürümqi, Xinjiang. (Reuters)
Many fashion, sport, and technology events have been canceled or have changed to be online. While the monetary impact on the travel and trade industry is yet to be estimated, it is likely to be in the billions and increasing. (Full article)
COVID-19 testing involves analyzing samples to assess the current or past presence of SARS-CoV-2. The two main types of tests detect either the presence of the virus or antibodies produced in response to infection. Molecular tests for viral presence through its molecular components are used to diagnose individual cases and to allow public health authorities to trace and contain outbreaks. Antibody tests (serology immunoassays) instead show whether someone once had the disease. They are less useful for diagnosing current infections because antibodies may not develop for weeks after infection. It is used to assess disease prevalence, which aids the estimation of the infection fatality rate. (Full article)
The COVID‑19 vaccines are widely credited for their role in reducing the spread of COVID‑19 and reducing the severity and death caused by COVID‑19. According to a June 2022 study, COVID‑19 vaccines prevented an additional 14.4 to 19.8 million deaths in 185 countries and territories from 8 December 2020 to 8 December 2021. Many countries implemented phased distribution plans that prioritized those at highest risk of complications, such as the elderly, and those at high risk of exposure and transmission, such as healthcare workers. (Full article)
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