As a respiratory virus, SARS-Cov-2 shares many of the same attributes and other commonly occurring viruses, such as influenza and pneumonia. A recent article on NCBI provides a very good overview of our understandings of COVID-19: (Source)

Viral respiratory infections result when a virus infects the cells of the respiratory mucosa; this can occur when virus particles are inhaled or directly contact a mucosal surface of the nose or eyes. Infected individuals shed virus into the environment by coughing or sneezing or even during quiet breathing. Virus shed during coughing and sneezing is often present in large droplets that fall out of the air within a short distance. If the virus falls on a surface and survives, it can be transmitted when someone touches the infected surface and then touches their nose, eyes, or mouth. Virus is also spread by the airborne route in the form of small (<5 μm) droplet nuclei that can remain suspended for long periods of time and can be inhaled into the lower respiratory tract.

Different viruses typically target general areas of the respiratory system. The body’s natural defense mechanisms filter out many pathogens. However, depending on the degree of exposure and defenses of the respiratory tract, some viruses can still get through to host cells.

When a person is infected with a respiratory virus, there is an incubation period before onset of clinical signs and symptoms. During the incubation period, the virus attaches to and infects cells, replicates its genome, and spreads to infect adjacent cells. The incubation period for influenza is short, typically 1–2 days, whereas for SARS-CoV-2, it is 4.5–5.8 day

During the incubation period, our bodies and respiratory defenses respond through our innate immune system.

The immune system responds to viral infection with cellular and humoral (antibodies, complement, and antimicrobial peptides) responses. These responses are initiated by the innate immune system, which recognizes pathogens and induces production of proinflammatory cytokines and chemokines. This is followed by responses of the adaptive immune system, which consists of T cells, which can directly kill virus-infected cells, and B cells, which produce pathogen-specific antibodies in the serum and at mucosal surfaces

Many people who contract the virus are able to successfully mount an effective response – especially those under the age of 60. The extent to which are natural innate defenses can successfully mitigate symptoms and severity is still being researched and investigated.

The spectrum of disease with SARS-CoV-2 ranges from asymptomatic infection to severe, often fatal disease. Patients with mild disease (80%) have fever, cough, sore throat, loss of smell, headache, and body aches. Moderate illness is characterized by involvement of the lower respiratory tract.

As of August 10, 2020, over 20 million individuals have contracted COVID-19 and almost 750,000 have perished. We have the opportunity to learn, understand, and prevent more pain and suffering – worldwide.

Read the full article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237932/