When you catch a virus it will hijack your metabolic processes for its own replication. The virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which is at the heart of the current global pandemic of the associated disease Covid-19 is no exception. It hooks into the body’s cellular processes leaching energy and exergy (energy that does work) so that it can duplicate its genetic code and build the proteins it needs to create copies of itself. Obviously, such an energy drain gives rise to some of the symptoms while others are caused by the body’s immune response that attempts to stop the virus in its tracks.
Writing in the International Journal of Exergy, a research team from Turkey explains how this novel coronavirus first reported in late 2019, causes a cluster of symptoms not commonly seen in other viral infections: severe pneumonia, pulmonary inflammation, and fibrosis. These symptoms reduce gas exchange between the air sacs, the alveoli, within the lungs, and the blood capillaries that carry oxygen away from the lungs and around the body. As such, patients experience diminished oxygenation of their blood haemoglobin. This then has an effect on metabolic rate.
If metabolic rate falls by one third, then in thermodynamic terms the fall in exergetic and energetic magnitude associated with the damage can be 0.46 and 0.45 Watt per kilogram of body weight, respectively. If the decline is a two-thirds decrease, the exergetic and energetic magnitude of the damage can be 0.92 and 0.90 W/kg, the team reports. Those are the figures for an 18-year old patient. For a putatively more vulnerable 70-year old, they would need to generate almost a fifth as much energy or exergy to compensate for the damage caused by the metabolic decline. This, partly explains why it is harder for older patients to cope with this virus and why they suffer worse symptoms. Additionally, if they have other underlying health conditions such as diabetes or lung disease, then the burden is even greater.
Having such information in hand will not only assists in our understanding of the progression and prognosis of this novel disease but may well point to improving how we treat it to save patients from severe morbidity or even mortality.
Yilmaz, B., Ercan, S., Akduman, S. and Özilgen, M. (2020) ‘Energetic and exergetic costs of COVID-19 infection on the body of a patient’, Int. J. Exergy, Vol. 32, No. 3, pp.314–327.