ANALYTICAL & LABORATORY EQUIPMENT
COVID-19: A TALE OF TWO CONDITIONS
Steve Walton explores why some Covid-19 patients are experiencing two stages of the condition
What can a patient’s blood tell us about Covid-19?
T
he coronavirus SARS CoV-2 (severe acute respiratory syndrome coronavirus 2), which causes Covid-19, may have been named
prematurely. As more has become known about the infection, the severe disease does not appear to be a respiratory syndrome at all. Patients who only have a respiratory illness tend not to have a severe condition, while patients who develop a severe condition tend to have non-respiratory conditions, primarily thrombotic or hyper-immune states. Why should this be? Although scientists and clinicians still do not fully understand what Covid-19 does to a patient, several facts have emerged over the past months that at least allow us to speculate (or for the scientists, hypothesise) on what is happening. It appears that when fi rst infected with
the virus patients suff er no symptoms (asymptomatic) for the fi rst 48 to 72 hours. During this period they are contagious and capable of spreading the
infection to others. After this initial lag phase the patient then progresses down one of two paths: either they remain asymptomatic; or they develop a cough and fever, which may require them taking to their beds, as with fl u. T e patients who remain symptom
free pose a large threat to the rest of the population, as they tend to carry on with normal life, unaware that they are passing on the virus to people they meet. Identifying these carriers is diffi cult and requires back tracing from patients who develop symptoms. Patients who develop symptoms again divide in to two groups, those that after nine or 10 days start to get better, and those that after nine to 10 days get markedly worse. For the patients that start to improve after this time they tend to fully recover like after fl u. Up to this point patients can be classed as having one condition, a respiratory illness, albeit not acute.
THE SECOND CONDITION It is the patients who deteriorate after about a week to 10 days that develop a second condition. T is second condition, although initiated by becoming infected with SARS Cov-2, does not appear to be directly related to viral activity, but is more probably due to the patient’s body being unable to control its defence mechanisms. When a human body becomes infected
several distinct but interactive defence systems are activated. T ese include the coagulation system; the immune system both cellular and chemical, the complement system (a system which can puncture bacteria) and a little known or understood system called the Kinin-Kallikrein system, which controls infl ammation, blood pressure control, coagulation and pain. All of these systems are delicately controlled by a series of activators or inhibitors which work through a series of positive and negative feedback loops to by and large maintain
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