When a respiratory virus infects the lungs, every cough or sneeze may release air-borne droplets containing infective viruses. Once a person is infected, they can display symptoms ranging from a mild flu-like disease to a severe case of infection. Typical symptoms reported are fever, a dry cough, muscle pain, fatigue and in severe cases, difficulty in breathing or shortness of breath.
To destroy the virus, the immune system recruits immune inflammatory cells to help the body fight the infection. These inflammatory cells flood an area to attack and destroy the pathogens. If the body is successful in controlling the infection, and if it is in balance, the inflammatory responses are down-regulated (decreased) and the natural healing process starts.
If, however, the immune system cannot eliminate the infection, the inflammatory response is upregulated and too much inflammation occurs, causing damage to healthy lung tissue.
Once lung damage has occurred, it becomes a prime environment for bacteria and other pathogens to multiply, often resulting in pneumonia. Infected patients may develop bi-lateral pneumonia (i.e., in both lungs) as has occurred in the current epidemic. At this point, if available, patients may be put on ventilators to assist in breathing.
Death may occur if the lungs, flooded with fluids and other cellular debris, are unable to take up oxygen. Sometimes, even if the person survives, the excessive inflammatory response may result in scaring and stiffening of lungs and permanent lung damage.
In addition to lung specific reactions, uncontrolled, “run-away” inflammation, can result in a “cytokine storm” or a condition called cytokine release syndrome. [Cytokines are immune messengers.] This phenomenon is the result of the immune system going “rogue” and releasing cascades of inflammatory immune cells and proteins (cytokines). The onslaught of inflammation may overwhelm the body, leading to blood pressure drop, weakened lung blood vessels, the inability of oxygen to get to the organs, organ failure and even death.
Such a “storm” can be triggered by a significant viral or bacterial infection or other health issues. During the early 2000’s, cytokine storm syndrome often resulted in the deaths of many individuals infected with SARs. It is likely that cytokine storms play a major role in the deaths of individuals, both younger and old, during the current epidemic.
Summary
Certain conditions may induce the release of massive amounts of inflammatory cells and their cytokines resulting in significant levels of uncontrollable inflammation.
https://mmbr.asm.org/content/76/1/16
https://jitc.biomedcentral.com/articles/10.1186/s40425-018-0343-9
