The viral infections of respiratory apparatus are highly contagious and they can caused
by different pathologies like: flu virus, parainfuenza virus, respiratory syncytial virus, coronavirus, Rhinovirus, Coxsackivirus, Adenovirus, Bocavirus, Metapneumovirus.
A virus is a small infectious organism, much smaller than a fungus or bacterium, that needs to invade a living cell in order to replicate itself. The virus adheres to the guest cell, penetrates it and releases its DNA or RNA inside the cell. DNA or RNA virus is the genetic material con- taining the needed info to replicate itself. The genetic material gets the control of the cell and force it to replicate the virus. Generally, the infected cell dies because the execution of its nor- mal functions is impeded. Before dying, the cell releases new virus keeping infecting other cells.
Among the emergent viruses that can cause respiratory infections these can be found:
SARS-CoV identified for the first time in 2002;
Avian influenza caused by H5N1, H7N9 virus;
MERS-CoV identified in 2012;
New Coronavirus called SARS-CoV-2.
The viral particles of SARS-CoV-2 have a spherical shape with a diameter of 100-160 nm. They show a lipidic envelope where the surface glycoproteins are anchored, conferring to the viral particle a characteristic crown shape, hence the name coronavirus. The genome is consti- tuted by single chain RNA with positive polarity of about 30kb. The virus presents 4 structural proteins and 16 non-structural proteins. The virus attack to the cell is mediated by the interac- tion of the Spike protein with cell receptor constituted by angiotensin convertase (ACE2) fol- lowed by internalization and fusion with endosome membrane through protease activity and consequent release of genomic RNA in the cytoplasm. This will immediately result in the poly- proteins pp1 a and pp1 ab and, then, processed in order to give the replicase and other not- structural proteins, responsible for genome replication and structural and accessory proteins expression preceded by a discontinuous transcription of sub-genomic RNA with negative po- larity where the respective messenger RNAs (mRNAs) are synthetized. Then the viral proteins assembly with genomic RNA to which follows the release of new viral particles. The corona- viruses belong to the Coronaviridae family. In December 2019 the new coronavirus has been identified and on December 7th 2020 the nucleotide sequence, available in few days, showed a genetic identity of 80% with SARS-CoV-1, previously identified in 2002. This virus, called SARS-CoV-2, is so highly contagious for humans to induce the World Health Organization to declare the status of pandemia.
The analysis in patients for SARS-CoV-2 virus research will be carried out on nucleic acid (RNA) appropriately isolated from high/low respiratory tract swab, by Real-Time RT PCR Simplex that identifies the new coronavirus disease agent (COVID-19) using as target two re- gions of N gene (N1 and N2) coding for viral nucleocapsid and as control the human P RNase (RP).
The Real-Time RT PCR is based on three main steps: isolation of virus RNA in the samples, RNA reverse transcription and real time amplification of cDNA.
The SARS-Cov-2 kit allows the identification by Real-Time RT-PCR technique of SARS- CoV-2 virus, in particular with fluorophore FAM identifies N, with fluorophore VIC identifies N2 and with fluorophore FAM the Mix RP. Kit Ampli SARS-CoV-2 has a specificity and a sensitivity of 99%.
