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Covid-19: a puzzle with many missing pieces

BMJ 2020; 368 doi: (Published 19 February 2020) Cite this as: BMJ 2020;368:m627

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Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2)

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Re: Covid-19: a puzzle with many missing pieces. Air pollution, climate and obesity could be the COVID 19 puzzle missing pieces

Dear Editor

The features most associated with novel coronavirus disease 2019 (COVID-19) infection and its respiratory complications are male sex, older age, cardiovascular disease, diabetes and perhaps higher BMI [1-4], but assessment of obesity is rarely reported in clinical studies.

An article regarding COVID-19 fatalities In Italy didn’t mention obesity as a comorbid disease associated with death and in a recent report from ISS about comorbid conditions in SARS-CoV-2 positive deceased patients, obesity is present in only 11,8 %, whilst type 2 diabetes accounts for 32% and hypertension for 69,7% of deceased patients [5-7]: these data appear to be inexplicably in relation to the known strong association between obesity and these pathologies. In Bergamo, where the disease is particularly severe, a large portion of adult (36.2%) and young population (23.9%) is overweight or obese [8]. Patients with BMI ≥ 40 kg/m2 are at risk for flu complications [9]. Excess fat is known to be associated with several respiratory conditions [10], and the possible link between severe pulmonary manifestations of COVID-19 and obesity is conceivable.

Recent evidence indicates that accumulation of adipose tissue within the lung of obese subjects correlates with inflammatory infiltrate [11]. Air pollution may induce lung dysfunction and some studies have highlighted the possibility that adipose tissue -- namely, visceral fat -- may mediate air pollution-induced lung dysfunction [12-13]. Furthermore, it is well known the causal association between pollution and obesity and related metabolic derangements [14-15]. In fact, both air pollution and high adiposity are closely related to increased inflammation [16-17]. Most of the diseases reported in Italian deceased patients, especially respiratory and cardiovascular diseases, have also been shown to be associated with exposure to air pollution [18].

Evidence exists correlating viral infection with atmospheric particulate matter (PM) concentrations (e.g. PM10 and PM2.5) [19-21]. A recent study demonstrates that aerosol transmission of SARS-CoV-2 is possible, since the virus remains viable and infectious in aerosols for hours [22]. Atmospheric PM constitutes a carrier for both chemical pollutants and viruses and allows viruses to persist in the air in vital conditions for hours or days, depending on the relative humidity and temperature [23-24]. Wuhan and Po Valley are high polluted areas characterized by similar thermo-hygrometric conditions [25-27].

It is tempting to speculate that the spread of the infection -- as well as international travel and individual behavior -- is also linked to the local differences in total and aged population, air pollution and climate [28-29]. Accordingly these situations, and especially pollution, may explain the high virulence, the fast spread and the greater mortality of SARS-CoV-2 in Northern Italy, directly through PMs being a possible carrier of viable viral particles and indirectly through a chronic inflammatory stimulus, especially in obese subjects even if young.

Considering all the above, while we are waiting conclusive investigations, it is advisable to reinforce the importance of staying at home until the weather and pollution improve, in order to avoid breathing polluted air possibly coated by SARS-CoV-2 and to recommend not only social distancing but also individual risk factor management, limiting overeating and promoting, as far as possible, physical activity to avoid weight gain and a subsequent increase in the global prevalence of obesity.

Carla Lubrano MD PhD
Department of Experimental Medicine, Section of Medical Pathophysiology, Food Science and Endocrinology,
Sapienza University of Rome

Annamaria Colao MD PhD
UNESCO Chair for Health Education and Sustainable Development,
Federico II University of Naples

Conflict of interests
The authors declare no competing interest.

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Competing interests: No competing interests

21 April 2020
Carla Lubrano
assistant professor
Annamaria Colao (UNESCO Chair for Health Education and Sustainable Development, Federico II University of Naples)
Department of Experimental Medicine, Section of Medical Pathophysiology, Food Science and Endocrinology, Sapienza University of Rome
Viale Regina Elena, 324 00161 Rome, Italy