Question

Explain the pathophysiology of COVID-19 using any anatomical topics and terms.

Answer 1

In december 2019, a series of respiratory infections occurred in Wuhan, China. It was found to be due to a novel corona virus termed as SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2). Disease caused by this virus was named COVID-19.

SARS-CoV-2 invasion into host cells
Coronaviruses are enveloped, single-stranded RNA viruses which infect a variety of host species.

The life cycle of the virus in the host has 5 steps.

1. attachment: viruses bind to host receptors
2. penetration: they enter host cells through membrane fusion or endocytosis
3. biosynthesis: viral RNA enters the nucleus and make viral proteins
4. maturation: new viral particles are produced
5. release: Then it gets released out of the host cell

Coronaviruses consist of four structural proteins which help in pathogenesis

1. Spike (S): determines host tropism and diversity of coronaviruses
2. membrane (M)
3. envelop (E)
4. nucleocapsid (N)

Host response to SARS-CoV-2

When SARS-CoV-2 enters the human body, there will be mild to severe forms of respiratory symptoms.

Virus enters the lungs and destroys ACE2 (Angiotensin converting enzyme 2) which is seen on epithelial cells in the alveolar space.

Our lungs have alveolar macrophages, epithelial cells and dendritic cells as part of innate immunity.

When virus causes infection, apoptotic epithelial cells are phagocytized by macrophages and dendritic cells. It causes antigen presentation to T lymphocytes. CD4+ T cells activate B cells and produce antibody. CD8+ T cells kill virus infected cells.

COVID-19 patients showed abnormal respiratory findings, increased leukocyte count and increase in inflammatory cytokines like IL7, IL8, IL9, IL10,IL1-β, IL1RA,MCP1, GCSF, GMCSF, IFNγ.

Patients with severe disease showed increase in IL2, IL7, IL10, MCP1, TNFα and GCSF which are responsible for the severity of infection.

Symptoms

Incubation period widely varies within

Most common symptoms are fever, cough, fatigue, headache, dyspnea and diarrhea.

Chest CT scan presents as pneumonia.

Transmission

Person-to-person transmission is through direct contact or droplets transmission by sneezing or coughing from infected individual