As health care providers take care of exceptionally high numbers of severely ill people, the Covid-19 pandemic has become an unprecedented event in modern medical practice. These providers reveal that the novel coronavirus causes the bodies of a certain proportion of the patient population to behave in mysterious ways. They might be right in some cases and not in others.
Happy hypoxia, blood clots, and anosmia (or lack of smell)
Covid-19 causes patients to exhibit some unusual symptoms for a respiratory infection and some others discerned by doctors mostly because of the magnitude of the number of people infected. As the pandemic continues, physicians and the public strive to distinguish them to understand better and explain the virus. Below are three symptoms that beg for more explanation than the specific pneumonia-related ones.
News stories addressed the presence of "happy hypoxia," a phenomenon in which people with low blood oxygen levels do not feel short of breath and actually comfortable as a clinical puzzle. At baseline, humans need a steady supply of fresh oxygen, exchanging it for carbon dioxide in millions of lung air sacs, and producing CO2 waste as a side effect of normal metabolism. When a portion of the lungs encounters a complete blockage of air or blood flow, that exchange doesn't happen, and oxygen levels drop. Exchanging more quickly than oxygen, carbon dioxide can still leave the lungs provided the remaining lung tissue is comparatively healthy and not hardened by age or disease.
Although it results in low oxygen and carbon dioxide levels, people can actually feel pretty comfortable with the former if they are not exerting much energy. Before the pandemic, doctors occasionally saw this same pattern in people with healthy lungs who had developed bacterial pneumonia called lobar pneumonia. However, doctors did not have to evaluate hundreds of thousands of people with respiratory problems in such a short period.
Easy coagulation of blood
One of these strange symptoms is blood clot formation in people with more severe forms of the disease. Chinese and Italian scientists started to establish a relationship between coronavirus and blot clotting linking the letter to respiratory failure as early as March 2020. In April 2020, Sharon E. Fox et al. also conducted autopsies on four African African decedents aged 44-76 whose lungs indicated bilateral pulmonary edema and dark hemorrhage patches. On April 9, another group of scientists led by Cynthia Magro published their paper about skin and lung tissues from five patients with severe Covid-19, all of whom were marked by respiratory failure and three by a purpuric skin rash.
The clot formation process in human blood involves hundreds of proteins, cells in a series of enzyme activation events with serine proteases stimulating the proteins. Physicians specialized in blood diseases generally observe patterns in blood tests as well as protein and cell abundance to point at the origin of a coagulation issue.
But the clotting in numerous severe Covid-19 infections eluded that effort making it hard to ascertain the root cause of clotting in these persons. However, another recent study conducted by Harvard Medical School researchers at Massachusetts General Hospital and published on August 21, 2020, in the American Journal of Hematology shed light on the question by referring to factor V as the main culprit.
The study said that patients with high blood clotting protein factor V levels and admitted with a critical Covid-19 state run a higher risk for grave injury from blood clots including deep vein thrombosis or pulmonary embolism, while critically ill patients with low levels of factor V seem to be at heightened risk for death from a form of coagulopathy that is similar to disseminated intravascular coagulation (DIC). DIC is an overwhelming, often deadly abnormality in which blood clumps form in little vessels in the body, causing exhaustion of clotting factors as well as proteins that regulate coagulation. However, Yogen Kanthi, and Jason Knight, M.D., Ph.D., co-corresponding author, showed in the study published in November 2020 that the virus triggers the production of antibodies circulating through the blood, causing clots in people admitted to hospitals with the disease.
Loss of smell and taste
Some relatively common Covid-19 complications are less common in other infections like the loss of smell and taste. A prepublication study by a group of German authors compared smell in 45 coronavirus-positive people with 45 uninfected people concluding that 40% of infected people lost their sense of smell. Another French study found a loss of smell lasting an average of 9 days in almost 50% all people infected with Covid-19. 85% of those people suffering from the loss of smell also had the same issue with their sense of taste. Despite the anecdotal reports that highlight the absence of other symptoms with loss of smell, the French researchers remarked that 60% of people with loss of smell had a runny nose.
Prior to Covid-19, a variety of conditions and infections were studied by doctors in terms of their potential to impair smell. Loss of smell in head colds has been generally thought to result from nasal passage mucus and swelling blocking smell receptors. However, persistent swelling of the passages is also thought to kill the nerve cells that emit smell sensation to the brain bringing about the inability to smell (for a certain period) even after the swelling is gone.
Coronavirus-related smell loss may be a little unusual as it is reported by many people relatively early in infection and usually without nasal passage inflammation. Those peculiarities made some scientists question if Covid-19 affected the nerves involved in sensing smell or other cells in the nasal passages' lining.
As with all weird infection-related symptoms, humanity needs further research from scientists to really understand what is going on.