SARS-CoV-2: How does the little monster make you sick?

A SARS-CoV-2 particle enters a person's nose or mouth and floats in the airway until it brushes against a lung cell that has an ACE2 receptor on the surface. The virus binds to that cell, slips inside and uses the cell's machinery to help make copies of itself. They break out, leaving the cell for dead, and penetrate other cells. Infected cells send out alarms to the immune system to try to neutralize or destroy the pathogens, but the viruses can prevent or intercept the signals, buying time to replicate widely before a person shows symptoms. The more viral particles that get into the lungs, the more damage to the lungs that is probably happening. 

Credit: The Trending Times

The amount of particles a person is exposed to can affect how likely they are to become infected and, once infected, how severe the symptoms become (from mild to severe symptoms, or even death). It appears that symptoms are showing up in infectors within 14 days of exposure to the virus. COVID-19 symptoms include cough, fever or chills, shortness of breath or difficulty breathing, muscle or body aches, sore throat, new loss of taste or smell, diarrhea, headache, fatigue, nausea or vomiting and congestion or runny nose. 

References

Hoffmann, Markus, et al. "SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor." Cell (2020).

Wrapp, Daniel, et al. "Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation." Science 367.6483 (2020): 1260-1263.

Van Doremalen, Neeltje, et al. "Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1." New England Journal of Medicine 382.16 (2020): 1564-1567.