(Selected Tables and Figures referenced, but not present in this blog
can be found in their corresponding Science Version blogs)
Reported illnesses with the novel coronavirus have ranged from mild symptoms to severe illness and death. The symptoms may appear 2 to 14 days after exposure (based on the incubation period). As with any infectious disease, the array of symptoms can vary considerably, but there are eight cardinal symptoms in adults and children (and other possibilities) which are the defining complex of the clinical disease (Table 7.1).
Elderly and immune-compromised patients are at greater risk of contracting the virus and for poor outcomes. However, significant numbers of young and healthy people are also being reported with severe infections, though generally with better outcomes. Spread occurs through respiratory droplets produced when an infected person coughs or sneezes. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs.
Older age, obesity, and comorbidities have consistently been reported as the greatest risk factors for unfavorable prognosis or protracted disease, called “post-COVID syndrome,” “long COVID,” or “long haulers syndrome.” This syndrome, however, is found in a full range of COVID-19 patients, with symptomatology ranging from severe to nonexistent. The syndrome itself includes all sorts of problems with inflammatory responses in the brain (“brain fog”), around the heart (myocarditis), around the nerves (neuropathies), around the muscles (myosititis), etc. It’s clear that in addition to the immediate clinical effects of SARS-CoV-2, the novel coronavirus can have long-term manifestations, experts say. Less clear so far has been how the number and types of comorbidities influence outcomes. All positive patients should be quarantined for up to 14 days. Some indirect biomarkers are being identified as diagnostic indicators for the degree and severity of a SARS-CoV-2 infection. Malfunction of interferon (IFN-1) was identified as attributing to an increase of at least 3.5% of patients with a life-threatening disease. Other studies of elevated concentrations of inflammatory cytokines and blood markers including C reactive protein, lactate dehydrogenase, and other digestive enzymes demonstrating that the gut microbiome is linked with the severity of COVID-19. The gut microbiota dysbiosis (imbalance) after disease resolution can also contribute to persistent symptoms (“long COVID”). Diagnostic tests for COVID-19 infection include an "antigen test" that reveals if a person is actively infected with the SARS-CoV-2 virus. The test detects certain proteins that are part of the virus. Antigen tests aren’t as sensitive as molecular tests, but are readily available. A molecular genetic test (PCR test) detects the genetic material of the virus using a lab technique called polymerase chain reaction (PCR). Molecular tests are considered very accurate (kind of the gold standard) when properly performed by trained personnel. Antibody tests check a person’s blood by looking for antibodies, that may (or may not) tell if the person had a past infection with the coronavirus. Neutralizing antibodies are specific to an antigen (the virus) and thus provide protection only against the specific disease associated with the virus. If the person is exposed to the antigen again, the antibodies produce “memory” toward the disease (remember the Bm cells and anamnestic protection from back in Blog #5?). There are however increasing reports of reinfection with the novel coronavirus suggesting that some coronavirus antibodies may not be neutralizing. Finally, genome sequencing is essentially determining the order of chemical “bases” of a DNA molecule (see Blog #10). Next generation sequencing (NGS) efforts in the early stages of COVID-19 helped determine the structure of the virus, as well as its early mutations that increased transmissibility and produced a massive pandemic. Genome sequencing is essential in identifying, dealing with, and tracking the spread of the newly emerging and increasingly virulent and transmissible SARS-CoV-2 variants. Such transmissibility suggests that these variants are already widespread. With enough mutations, a strain may be able to evade current vaccines. If a vaccine-resistant strain is identified in the future, vaccine research will have to be directed towards a "universal vaccine" through evidence-based data. That evidence will only come from genome sequencing, AI and big data analytics.
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