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Coronaviruses are a family of viruses, which can cause serious pathologies such as pneumonia-like disease. The new coronavirus first reported in Wuhan, Hubei province, China, since mid-December 2019 is now known as the Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) which causes a disease named COVID-19 by the World Health Organization (WHO), acronym for COronaVIrus Disease 2019. The global situation of COVID-19 has been described by WHO as a pandemic after being spread worldwide. The SARS-CoV-2 is affecting 212 countries and territories around the world. SARS-CoV-2 is the seventh coronavirus known.to.infect.humans, as Middle.East respiratory.syndrome (MERS-Cov) and SARS-Cov SARS-CoV-2 causes respiratory.and intestinal.infections however HKU1, NL63, OC43 and 229E are associated with mild symptoms (Andersen et al. 2020). SARS-Cov first emerged in the Guangdong province, China (2002 - 2003 epidemic). It affected around 8.000 individuals in more than 30 countries and has caused the death of 800 patients (Du Toit, 2020). Middle East respiratory syndrome (MERS) represents an important respiratory disease accompanied by mortality in the third of patients. dromedaries are reported as an important source of infection. SARS and MERS coronaviruses likely originated in bats and have been transmitted directly to humans from market civets and dromedary camels (Haverkamp et al. 2018). The COVID-19 pandemic has required border closedown, city lockdown, closure of schools, universities and laboratories in multiple countries. In Algeria the first cases were reported on March 1st in Blida province, near Algiers (http://covid19.sante.gov.dz/carte). |
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The life cycle of coronavirus in host cell Abbreviations
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Detection of SARS-CoV-2 using qRT-PCR • Reverse transcription: 50 °C for 15 min (01 cycle) qPCR Principle In quantitative PCR we usually use a specific fluorescent probe in addition to primers in order to detect the amplification of the target gene. The probe sequence is labeled at the 5’ end with a fluorescent reporter dye (F) and at the 3’ end with a quencher dye (Q). In case the probe does not anneal to a specific sequence, the fluorescent reporter will stay physically close to the quencher which will cause the quenching of the reporter’s fluorescence. However, if the probe anneals to a specific sequence on the target gene, it will be degraded by the 5’-3’ exonuclease activity of Taq DNA polymerase. The fluorescent reporter will be then released from the quencher which will be no longer close enough to absorb the emission from the reporter dye. The fluorescent signal is thus generated and detected by CCD camera in a LightCycler. The threshold cycle or. Ct value is the number of cycles required for the fluorescent signal to cross the fluorescence threshold (the real signal could so be distinguished from background signal). Ct level is inversely proportional to the amount of target RNA in the sample. The lower is the Ct level the bigger is the amount of target RNA in the sample. Abbreviations References |
