Clinical Description of COVID (PartA)

COVID Clinical Description (excerpt)

Part I

The CoVs have become the major pathogens of emerging respiratory viral outbreaks. They are a large family of single-stranded RNA viruses (+ssRNA) that can be isolated in different animal species. These viruses can cross species barriers and can cause, in humans, illness ranging from the common cold to more severe illnesses such as COVID.

Etiology

CoVs are positive-stranded RNA viruses with somewhat crown-like appearance under an electron microscope (coronam is the Latin term for crown) due to the presence of spike glycoproteins on the envelope.

CoVID. Thus, CoVID belongs to the betaCoVs category. It has round or elliptic and often pleomorphic form, and a diameter of approximately 60–140 nm.

Transmission electron microscopic image of an isolate from the first U.S. case of COVID-19, formerly known as 2019-nCoV. The spherical viral particles, colorized blue, contain cross-section through the viral genome, seen as black dots

The subfamily Orthocoronavirinae of the Coronaviridae family (order Nidovirales) classifies into 4 genera of CoVs: Alphacoronavirus (alphaCoV), Betacoronavirus (betaCoV), Deltacoronavirus (deltaCoV), and Gammacoronavirus (gammaCoV).

The betaCoV genus divides into 5 sub-genera or lineages.

Genomic characterization has shown that most likely bats and rodents are the gene sources of alphaCoVs and betaCoVs.

While avian species seem to represent the gene sources of deltaCoVs and gammaCoVs.

Members of this large family of viruses can cause respiratory, enteric, hepatic, and neurological diseases in different animal species.

Currently at least 7 human CoVs (HCoVs) — capable of infecting humans — have been identified.

Pathophysiology

CoVs are enveloped, positive-stranded RNA viruses with nucleocapsid. In CoVs, the genomic structure is organized in a +ssRNA of approximately 30 kb in length — the largest known RNA viruses — and with a 5′-cap structure and 3′-poly-A tail. Pathophysiology and virulence mechanisms of CoVs, and therefore also of CoVID have links to the function of the nsps and structural proteins.

Transmission

section A

Because the first cases of the CoVID disease were linked to direct exposure at the Huanan seafood wholesale market in Wuhan, the animal-to-human transmission was presumed as the main mechanism. Similar to that previously identified during SARS. The virus is transmitted from human-to-human, and symptomatic people are the most frequent source of CoVID spread.

Transmission is believed to occur through respiratory droplets (particles >5-10 μm in diameter) from coughing and sneezing and predominately talking. Aerosols are less than 5um in size and respiratory droplets are more than 5um in size. These are distributed from the human facial region, primarily mouth (saliva) and nose.

Pre and asymptomatic individuals may contribute up to 80% of CoVID transmission. The spread, in fact, is primarily limited to family members, healthcare professionals, and other close contacts (6 feet, 1.8 meters). As has been documented in epidemiological studies worldwide.