Reports have shown that up to 20 percent of persons infected with SARS-CoV-2 develop severe disease and need to be treated in a hospital.
Of these hospitalized patients, up to one-fourth need intensive care. Cultural differences in medical practice, pre-disposing or risk factors, and availability of tests, however, affect the reported rates of intensive care unit (ICU) admissions.
In China, ICU admission rates ranged from seven to 26 percent. In Italy, five to 12 percent, and in the U.S., in an elderly patients group from a nursing home were admitted to the ICU, but a study on a bigger group that included younger patients showed 4.9 to 11.5 percent ICU admission.
Among those who develop severe disease, studies showed that difficulty in breathing occurs at an average of six and half days after the start of signs/symptoms but progression to severe lung disease known as acute respiratory distress syndrome or ARDS can occur at an average of just two and half days after the start of difficulty in breathing (dyspnea).
Among those who are very sick, failure of lung function (ARDS) is the main finding. Blood levels of oxygen become very low so that 42 to 100 percent of patients would need mechanical ventilation. Extracorporeal membrane oxygenation (ECMO), a procedure in which blood is made to pass through a machine for oxygenation, is also done in patients in severe cases. Most complications resulting from ARDS and low blood oxygenation are kidney failure, liver damage, heart injury that includes irregular rhythm, fluid accumulation or inflammation around the heart (pericardial effusion and pericarditis), or heart attack.
Heart complications may be a late complication even after lung function has improved. Patients who develop kidney failure generally require kidney support treatments like dialysis.
In Covid-19, disseminated infection or sepsis, shock, and multi-organ failure are less common compared to ARDS caused by other infections.
In some patients with severe Covid-19, there is laboratory evidence of marked inflammatory response – “cytokine storm.” They have elevated markers of inflammation like D-dimer, ferritin, interleukin-6, and cytokines. Studies are being done on the use of agents that counteract or minimize the inflammatory response. Tocilizumab, sarilumab, and siltuximab, drugs classified as interleukin-6 receptor inhibitor are being assessed in clinical trials. Treatments like hemoperfusion are done to remove inflammatory substances; these are adsorbed or trapped on the surface of a cartridge as a patient’s blood passes through it.
Studies have shown that age appears to be the major risk factor for the development of ARDS. This is the reason why senior citizens are advised to observe social distancing and thus avoid undue exposure. Adults of any age, however, may develop severe disease if with comorbidities like obesity, hypertension, and diabetes mellitus. Factors that also predict severe disease among adults of any age is history of high fevers 39 degrees Celsius and above, history of smoking, and abnormalities in laboratory results related to the disease.
Persons who became infected with SARS-CoV-2 produce antibodies but it is still uncertain if these antibodies are protective enough to prevent a repeat infection. If these antibodies are protective, it is not yet established how long they can protect the person.
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