Decision letter: SARS-CoV-2 shedding dynamics across the respiratory tract, sex, and disease severity for adult and pediatric COVID-19

Previously, we conducted a systematic review and analyzed the respiratory kinetics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Chen et al., 2021). How age, sex, and coronavirus disease 2019 (COVID-19) severity interplay to influence the shedding dynamics of SARS-CoV-2, however, remains poorly understood. We updated our systematic dataset, collected individual case characteristics, and conducted stratified analyses of SARS-CoV-2 shedding dynamics in the upper (URT) and lower respiratory tract (LRT) across COVID-19 severity, sex, and age groups (aged 0-17 years, 18-59 years, and 60 years or older). The systematic dataset included 1266 adults and 136 children with COVID-19. Our analyses indicated that high, persistent LRT shedding of SARS-CoV-2 characterized severe COVID-19 in adults. Severe cases tended to show slightly higher URT shedding post-symptom onset, but similar rates of viral clearance, when compared to nonsevere infections. After stratifying for disease severity, sex and age (including child vs. adult) were not predictive of respiratory shedding. The estimated accuracy for using LRT shedding as a prognostic indicator for COVID-19 severity was up to 81%, whereas it was up to 65% for URT shedding. Virological factors, especially in the LRT, facilitate the pathogenesis of severe COVID-19. Disease severity, rather than sex or age, predicts SARS-CoV-2 kinetics. LRT viral load may prognosticate COVID-19 severity in patients before the timing of deterioration and should do so more accurately than URT viral load. Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant, NSERC Senior Industrial Research Chair, and the Toronto COVID-19 Action Fund.

Background:Previously, we conducted a systematic review and analyzed the respiratory kinetics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Chen et al., 2021). How age, sex, and coronavirus disease 2019 (COVID-19) severity interplay to influence the shedding dynamics of SARS-CoV-2, however, remains poorly understood.Methods:We updated our systematic dataset, collected individual case characteristics, and conducted stratified analyses of SARS-CoV-2 shedding dynamics in the upper (URT) and lower respiratory tract (LRT) across COVID-19 severity, sex, and age groups (aged 0–17 years, 18–59 years, and 60 years or older).Results:The systematic dataset included 1266 adults and 136 children with COVID-19. Our analyses indicated that high, persistent LRT shedding of SARS-CoV-2 characterized severe COVID-19 in adults. Severe cases tended to show slightly higher URT shedding post-symptom onset, but similar rates of viral clearance, when compared to nonsevere infections. After stratifying for disease severity, sex and age (including child vs. adult) were not predictive of respiratory shedding. The estimated accuracy for using LRT shedding as a prognostic indicator for COVID-19 severity was up to 81%, whereas it was up to 65% for URT shedding.Conclusions:Virological factors, especially in the LRT, facilitate the pathogenesis of severe COVID-19. Disease severity, rather than sex or age, predicts SARS-CoV-2 kinetics. LRT viral load may prognosticate COVID-19 severity in patients before the timing of deterioration and should do so more accurately than URT viral load.Funding:Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant, NSERC Senior Industrial Research Chair, and the Toronto COVID-19 Action Fund.

Weight excess association with severity in children and adolescents with COVID-19: A systematic review.

Background:Which virological factors mediate overdispersion in the transmissibility of emerging viruses remains a long-standing question in infectious disease epidemiology.Methods:Here, we use systematic review to develop a comprehensive dataset of respiratory viral loads (rVLs) of SARS-CoV-2, SARS-CoV-1 and influenza A(H1N1)pdm09. We then comparatively meta-analyze the data and model individual infectiousness by shedding viable virus via respiratory droplets and aerosols.Results:The analyses indicate heterogeneity in rVL as an intrinsic virological factor facilitating greater overdispersion for SARS-CoV-2 in the COVID-19 pandemic than A(H1N1)pdm09 in the 2009 influenza pandemic. For COVID-19, case heterogeneity remains broad throughout the infectious period, including for pediatric and asymptomatic infections. Hence, many COVID-19 cases inherently present minimal transmission risk, whereas highly infectious individuals shed tens to thousands of SARS-CoV-2 virions/min via droplets and aerosols while breathing, talking and singing. Coughing increases the contagiousness, especially in close contact, of symptomatic cases relative to asymptomatic ones. Infectiousness tends to be elevated between 1 and 5 days post-symptom onset.Conclusions:Intrinsic case variation in rVL facilitates overdispersion in the transmissibility of emerging respiratory viruses. Our findings present considerations for disease control in the COVID-19 pandemic as well as future outbreaks of novel viruses.Funding:Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant program, NSERC Senior Industrial Research Chair program and the Toronto COVID-19 Action Fund.

In December 2019, a novel coronavirus was identified in Wuhan City, Hubei Province, China and later the disease was named coronavirus disease 2019 (COVID-19). On March 11, 2020, the World Health Organization (WHO) officially announced that COVID-19 had reached global pandemic status. This article summarized the understanding of the etiology, pathogenesis, epidemiology, clinical characteristics, diagnosis, treatment, rehabilitation, and prevention and control measures of COVID-19 based on the available data and anti-epidemic experience in China.

Diagnoses of coronavirus disease 2019 (COVID-19) from the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) were first reported in December 2019. Since its emergence from the Chinese province of Wuhan, the World Health Organization (WHO) has announced 162 million confirmed cases of the SARS-CoV-2 infection worldwide, and reported roughly 3.3 million deaths as of May 16, 2021.1 Stratified by country, the United States leads with nearly 33 million confirmed COVID-19 cases, followed by India, Brazil, France, Turkey, and Russia.2 Structural firefighters perform essential public safety work and have continued that work despite the challenges of COVID-19. Career firefighters typically have long work schedules (24 or 48 hours on duty followed by multiple days off) and eat and sleep at the station as part of a team/shift. Firefighters respond to multiple hazards which include fires and rescues. In many localities, firefighters are dual trained as emergency medical service (EMS) personnel and provide emergency medical care. Because of their close living quarters and contact with the public, including rendering patient care and transporting patients, it is likely that firefighters are at an increased risk of infection with SARS-CoV-2. The fire service is aware of the risk of infection and has quickly adopted the increased use of personal protective equipment (PPE) and modified policies and procedures aimed at reducing the risk to firefighters.3,4 However, very little attention has been paid to occupational risks that may increase the severity of COVID-19 or to the potential long-term consequences of COVID-19 that may pose specific concerns for firefighters. The purpose of this review is to 1) outline the pathogeneses of COVID-19, 2) explore clinical and mechanistic links between COVID-19 and cardiovascular disease, 3) review known risk factors for COVID-19 complications and their prevalence among firefighters, and 4) consider steps that can be taken to better understand the long-term consequences of COVID-19 in the fire service. The review is limited to occupational factors for structural firefighters and does not cover wildland firefighters, although we acknowledge that COVID-19 may also present special concerns for wildland firefighters. PATHOGENESIS OF COVID-19 The SARS-CoV-2 virus enters the body predominantly via the lungs, and often results in pronounced respiratory symptoms. Thus COVID-19 was initially described as a respiratory disease. Indeed, respiratory failure from acute respiratory distress syndrome has been shown to be leading cause of COVID-19 induced mortality.5 A study by Guan et al6 reported that the majority of COVID-19 related consequences feature pneumonia and acute respiratory distress, which is consistent with other analyses suggesting that about 40% of COVID-19 patients develop acute respiratory distress syndrome, and 20% of these syndromes are severe.7 Wang et al8 showed that 61% of the individuals that required intensive care due to COVID-19 developed acute respiratory distress syndrome. COVID-19 not only lead to respiratory symptoms, but also underlying respiratory conditions increase the likelihood of experiencing severe symptoms. Meta-analyses revealed that the odds of severe COVID-19 infection were 5.69 times higher if individuals who have a history of chronic obstructive pulmonary disease.9 The virus requires the cooperation of two key proteins, TMPRSS2, and angiotensinogen converting enzyme 2 (ACE2) to infiltrate the body via the lung pneumocytes. TMPRSS2 is a key cellular regulator of coronavirus spike protein (S protein), with the S1 domain of the S protein responsible for receptor binding and the S2 domain controlling membrane fusion. Thus, coronavirus requires the binding of the S1 region to a cell surface receptor followed by the S2 subunit mediated fusion of the viral and cellular membranes in order to enter its host.10 This process requires S protein priming, or cleavage, by host proteases at the S1and S2 domains of the virus. This process has been described as a principle step for the cellular entry of SARS-CoV-2.11 Following S protein cleavage, Sars-CoV-2 binds to and enters lung cells via the enzyme ACE2, which is highly expressed in alveolar type 2 cells.12 Dissimilar to the original SARS-CoV, it has been suggested that SARS-CoV-2 may have a higher affinity to ACE2 positive cells in the upper respiratory tract, exacerbating its potent and detrimental effects.11 ACE2 is a membranous protein and importantly, an inactivator of angiotensin II (AngII). The binding of SARS-CoV-2 to ACE2 in lung cells promotes the endocytosis of the ACE2-SARS-CoV-2 complex, resulting in a reduction of membrane ACE2 abundance and an increase in serum AngII.12 Thus, SARS-CoV-2's affinity for ACE2 could explain its downstream effects on vascular parameters, including alterations in systolic and diastolic blood pressures, as elevated plasma AngII can increase blood pressure via aldosterone-mediated vasoconstriction and sodium and water retention on the kidneys.13 Furthermore, increased plasma AngII is associated with increased risks of myocardial infarction and left ventricular hypertrophy.13 In addition, SARS-CoV-2 promotes inflammation via the AT1R.12 The AngII-AT1R axis activates pro-inflammatory transcription factors NF-kB and STAT3, upregulating pro-inflammatory cytokines such as TNFa and IL-6 family cytokines,12,14 possibly leading to vascular inflammation and disease. Furthermore, recent studies suggest that the Sars-CoV-2 protein ORF3a encourages an aggressive inflammatory response via NF-κB activation, chemokine secretion, Golgi fragmentation, ER stress, and cell death.15 ORF3a can also inhibit type I interferon (type I IFN) signaling, downregulate major histocompatibility complex (MHC) class I expression, and reduce CD8+ cytotoxic T cell activity. Specifically, Siu et al15 demonstrated that ORF3a encourages the binding of TRAF3 to cytoplasmic portions of TNF receptors, promoting ubiquitination, and processing of p105 to p50. P50 is generated by TRAF3 ubiquitin-ligase ubiquitination of p150 and 26S proteasome-mediated removal of p105C terminal sequences. P50 then binds to RelA, RelB, or C-Rel subunits to produce functional NF-κB, a transcription factor essential for pro-IL-1β expression. The prevalence of pro-IL-1β transcripts is a requirement for NLRP3 inflammasome activation. Therefore, ORF3a-mediated p105 processing into p50 can help activate the NLRP3 inflammasome and lead to a robust inflammatory response.15 Siu et al further demonstrated ORF3a's ability to induce ASC polyubiquitination via a TRAF3 ubiquitin-ligase.15 ASC is the adapter complex of the NLRP3 inflammasome, and polyubiquitination of ASC provides a nondegradative signal necessary for ASC activation, caspase-1 activation, and mature IL-1β protein formation.15 Ultimately, the studies mentioned above illustrate how COVID-19 can target the cardiovascular system through its mode of entry and lead to vascular inflammation and dysfunction via upregulation of pro-inflammatory signaling. COVID-19 AND CARDIOVASCULAR DISEASE Although SARS-CoV-2 was first described as a respiratory disease, cardiac tissue and blood vessels express ACE2 receptors and appear to be particularly prone to COVID-19 infection.14 The heart, an ACE2 expressing tissue, was studied during the Toronto SARS outbreak (SARS-CoV), and investigators found evidence of SARS-CoV RNA in 35% of autopsied hearts.16 COVID-19 acts in a similar manner to the previous SARS-CoV, indicating that individuals with cardiovascular disease (CVD) are more prone to severe complications of SARS-CoV-2 compared to healthy individuals. Initial research on CVD-induced complications of COVID-19 was conducted in China. Wang et al investigated the association between biomarkers of CVD and the exacerbation of COVID-19 in hospitalized patients and found that cardiac injury, defined as either elevated high-sensitivity cardiac troponin I (hs-cTnI) or ECG/echocardiographic abnormalities, was present in 7.2% of the patients.8,17,19 The study also found that 22% of COVID-19 patients in ICU had biomarkers of cardiac injury.8,17 Zhou et al reported that hs-cTnI levels were at or greater than the 99th percentile upper reference limit in 46% of non-survivors, compared to only 1% of survivors who had levels this high.17,18 Thus, it has become apparent that COVID-19 can have severe cardiovascular consequences. Ultimately, it is also becoming clear that the presence of CVD, or CVD risk factors, can increase the likelihood of severe complications of COVID-19. The observational study by Zhou et al described above, also reported that 8% of patients (13% of non-survivors) had been diagnosed with CVD and 38% (48% of non-survivors) had been diagnosed with hypertension.17,18 Furthermore, Wang et al found that comorbidity of COVID-19 and CVD was prevalent in 15% (25% requiring ICU care) of patients analyzed, and Guan et al reported that 2.5% (9% among those with intubation or death) of COVID-19 patients also suffered from coronary artery disease.10,11,14 Chen et al demonstrated that in a cohort of 99 COVID-19 infected individuals at the Wuhan Jinyintan Hospital, 40% had some manifestation of cardiovascular or cerebrovascular disease.19 Other researchers have also reported on the higher prevalence of hypertension among COVID-19 patients; one study that although reports 15% of COVID patients had hypertension, 36% of those who needed intubation or suffered death had hypertension. Another study reported 31% of patients with COVID-19 had hypertension; however, 58% of patients requiring ICU care had hypertension.6,8 These findings demonstrate a clinical link between COVID-19 and CVD. EFFECT OF COVID-19 ON CARDIOVASCULAR SYSTEM Following the COVID-19 outbreak, researchers have begun to investigate the mechanisms associating COVID-19 and CVD. Emerging evidence strongly suggests the SARS-CoV-2 infection decreases myocardial functioning. Previous research has demonstrated that SARS-CoV, resembling both the structure and function of SARS-CoV-2, perturbates myocardial functioning.20 Recent research analyzing the cardiac manifestations of the SARS-CoV-2 infection found that the most common cardiac abnormality (39% of patients at baseline) was right ventricular dilation and dysfunction, followed by left ventricular diastolic and systolic dysfunction (16% and 10% of patients at baseline, respectively).21 In this study, 20% of these patients had clinical deterioration, with 60% of them having right ventricle deterioration and 25% having left ventricle systolic and diastolic deterioration.20 Thus, it appears that COVID-19, similar to other severe hypoxic respiratory illnesses, impairs cardiac function mostly by a right ventricular pressure overload state. Myocardial injury involves a pronounced escalation in pro-inflammatory cytokine secretions, which is commonly seen in COVID-19 patients. Specifically, research has found that patients suffering from COVID-19 had an upregulation of the pro-inflammatory cytokines IL1B, IFNγ, IP10, and MCP1. Individuals in ICU admission for COVID-19 had higher concentrations of the cytokines GCSF, IP10, MCP1, MIP1A, and TNFα than those not in ICU.22 An increase in these molecules due to COVID-19 severity can lead to an activation and dysregulation of T helper cells.22 Imbalances in (type 1 and type 2) T helper cells can lead to respiratory dysfunction, hypoxemia, and myocardial injury.20 Interestingly, Huang et al noticed that type 2 T-helper cell cytokines (IL4 and IL10), that suppress inflammation, were upregulated during infection of SARS-CoV-2.20 A study of competitive athletes recovering from COVID-19 found that 15% (4/26) had cardiovascular magnetic resonance findings suggestive of myocarditis despite only 2 of the 4 participants with findings suggestive of myocarditis having had COVID-19 symptoms.23 Acute thrombotic events are another major complication in individuals fighting the SARS-CoV-2 infection. Blood hypercoagulability has been shown to be common among hospitalized COVID-19 patients.24 Elevated D-Dimer levels, associated with thrombus formation and breakdown, are also reported in COVID-19 patients, worsening over the course of the disease.24 A review by Terpos et al elegantly describes how thrombus degradation products including PT and aPT are consistently upregulated in individuals requiring ICU admission.24 COVID-19 has also been shown to induce acute pulmonary embolisms in certain individuals,24–27 and one study found that 30% of COVID-19 patients had acute pulmonary embolus, measured by a CT coronary angiogram.28 This rate of pulmonary embolus is higher than what is usually seen in critically ill patients without COVID-19 (1.3%).28 Ultimately, COVID-19 patients are at higher risk for thromboembolic events, leading to adverse cardiovascular health risks. The endothelium plays key roles in regulating blood flow, maintaining hemostatic balance, and in immune response. Emerging evidence suggests that a vascular disease process contributes to COVID-19 pathogenesis.29 Several studies have begun to elucidate the role of endothelial dysfunction with COVID-19. Epithelial dysfunction, specifically pulmonary endothelial damage, is a common manifestation observed in patients infected with SARS Cov-2 virus and other coronaviruses.26 Endothelium damage due to COVID-19 is thought to occur by multiple mechanisms, including: a dysregulated immune response, enhanced vascular permeability, and exacerbated presence of pulmonary edemas.26,30 Varga et al31 demonstrated endothelial cell dysfunction in vital organs of individuals after becoming infected with COVID-19. These authors presented convincing evidence to indicate that the SARS CoV-2 virus has direct effects on endothelial cells, possibly due to the fact that ACE2 is also widely expressed on endothelial cells in multiple organs.14 Thus, it appears that recruitment of immune cells and pro-inflammatory cytokines due to ubiquitous expression of ACE2 can result in extensive endothelial dysfunction and cellular apoptosis. THE EFFECTS OF OBESITY ON CARDIOVASCULAR HEALTH AND COVID-19 Obesity has been recognized as an important predictor of CVD risk and adverse cardiorespiratory outcomes. Genetic and clinical experiments have found that that obesity is causally related to many disease states including hypertension, diabetes mellitus type 2, coronary heart disease, stroke, atrial fibrillation, renal disease, and heart failure.32 Others have reported that around 75% of hypertension can be attributed to obesity.33 It is clear that this obesity-induced hypertension leads to renal dysfunction due to an increased sympathetic nervous state and upregulated renin–angiotensin system.33 Obesity has effects on the infection and exacerbation of the SARS-CoV-2 infection. Sattar et al propose that obesity and ectopic fat deposition might reduce both optimal cardiorespiratory and immune response mechanisms, two major factors that can lead to severe manifestations of COVID-19.32 Several studies have reported on an association between obesity and COVID-19. Hamer et al reported a two-fold risk ratio of being infected with COVID-19 for obese individuals compared to normal weight individuals.34 These risk ratios were adjusted for age, sex, and mutually for each lifestyle, and physical inactivity. Furthermore, obesity was identified as the risk factor that contributed greatly to the prediction of COVID-19 infection risk. Finally, Hamer et al calculated a Population Attributable Fraction (PAF), which corresponds to the prevalence of risk factors in a population and the strength of its association with an outcome (COVID-19).34 The PAF used adjusted effect estimates on lifestyle factors (smoking, physical inactivity, overweight, and obesity) and COVID-19 and found that the total PAF for the three unhealthy lifestyle factors was 51.4%.34 Specifically, overweight and obesity had a PAF of 29.5%, smoking had a PAF of 13.3%, and physical inactivity had a PAF of 8.6%. Overall, it has become quite clear through both mechanistic and clinical research that there is a powerful effect of obesity on COVID-19 infection and severity. POTENTIAL RELATIONSHIPS BETWEEN FIREFIGHTERS AND COVID-19 As discussed through this paper, there is a strong relationship between both pulmonary disease, CVD and COVID-19. While initial research has focused on risk factors that place individuals at increased risk for COVID-19 complications, this section details ways that occupational exposures and cardiovascular risk factors that are known to be prevalent among firefighters, might make firefighters an occupational group that is at high risk of developing COVID-19 complications and for whom the long-term effects of COVID-19 infection might be particularly problematic. As summarized in Tables 1 and 2 and discussed in the following section, there are multiple factors that are known to exacerbate the rate of infection or severity of infection with SARS-CoV-2 and that are occupationally associated with firefighting. TABLE 1 - Association Between Medical Conditions of COVID-19 and Firefighting Medical Conditions COVID-19 Research Fire Service Research 1. Pulmonary disease • Significantly associated with a severe COVID-19 infection (OR 5.69, 95% CI: 2.49–13.00)9• 30% of studied COVID-19 patients developed acute respiratory distress syndrome,28 61% of studied COVID-19 patients developed acute respiratory distress syndrome,7,8,28 with approximately 20% of these cases being severe8 • Decrements in respiratory function were two-to-four-times greater in firefighters than general population35• Pulmonary function is associated with frequency of fire exposure36• Those who transitioned to less active assignments might not be protected from pulmonary disease88 2. Cardiovascular disease • 15–40% of patients had some manifestation of cardiovascular or cerebrovascular disease7,8,19 • Firefighters with other comorbidities demonstrated unfavorable CVD and cardiorespiratory fitness profiles70 COVID-19, coronavirus disease 2019; CVD, cardiovascular disease. TABLE 2 - Association Between Risk Factors of COVID-19 and Firefighting Risk Factors COVID-19 Research Fire Service Research 1. Age • Significant association of older age (≥65 years) and risk of COVID-19 mortality• Ranging from an OR of 3.76 (95% CI: 1.15–17.39; P = 0.023) to 4.59 (95% CI: 2.61–8.04; P < 0.001)57,58 • 9% of the entire US firefighting cohort is 60 years of age or older55 2. Sex • Males have made up as much as 60.3–70% of patients hospitalized with the SARS-CoV-2 infection• Prostatic diseases are associated with elevations in COVID-19 induced cardiac injury (OR 1.505, 95% CI; P = 0.046)60• In males, each standard deviation increase in free androgen escalates risk of severe COVID-19 manifestations (OR 1.22, 95% CI: 1.03–1.45; P = 0.024)60 • 96% of the US fire service is comprised of men, and more than half of US metropolitan departments have no women firefighters55,62 3. Hypertension • 56.6% of New York City area COVID-19 patients had hypertension59• Significant associate of COVID-19 mortality (pooled OR 2.70, 95% CI: 1.40–5.24; P = 0.003)57 • Up to 30% of the entire fire service have hypertension63,72• 46% of males and 29% of females firefighters had blood pressure the of 1 or 2 58% of firefighters and of firefighters have Obesity • been as the one of COVID-19 obese individuals are at greater risk for severe COVID-19 • of firefighters = were as either overweight or of overweight and obese firefighters may the US Cardiovascular • troponin is associated with COVID-19 mortality risk (OR 95% CI: P < cardiac injury in 7.2% of patients, and in 22% of ICU of patients had right ventricular dilation and dysfunction, had left ventricular diastolic dysfunction, 10% had systolic • Acute of decreases can induce ventricular and of myocardial and blood and • increased ACE2 and TMPRSS2 in alveolar type 2 cells and • Decrements in were more than the rate in were related to frequency of fire but not to age, smoking or Firefighters who a during fire a times greater rate of compared to COVID-19, coronavirus disease 2019; vital Pulmonary from recent study indicate that in the respiratory function of firefighters years) was two-to-four-times greater than the in the general reports with findings and also that the of pulmonary function in firefighters is associated with the frequency of fire of fires are more potent of than previous on their occupational firefighters appear to be at an increased risk of pulmonary is less evidence that firefighting leads to increased pulmonary disease, but this is a pulmonary disease is associated with increased risk for developing a severe COVID-19 infection. Pulmonary Risk and the acute and long-term effects of and is a in the fire service. have that and can reduce firefighters in 1 by lung function often to Furthermore, et demonstrated an of in firefighters following a of with 30% of the cohort having a in of Other studies have shown that the in which firefighters for and of can cause decreases in and vital as as in serum cell protein and serum studies the effects of long-term and on health have been the results are A study conducted on firefighters from the fire showed that in the and were not associated with of firefighting in active and that the protective respiratory equipment used by the fire service to be the detrimental effects of enhanced and In addition, a review of studies from to that the of and on health is and limited by of and that firefighters in pulmonary However, a study by et found that the in were more than the rate and was related to frequency of fire but not to age, smoking or et further showed that active firefighters a greater in compared to those who had or firefighters who a during fire a times greater rate of compared to Other studies have shown that with respiratory use in et showed that after years of there was a 10% in the of firefighters who to the World Thus, there is but not evidence that to and can both and pulmonary function in firefighters, use of respiratory protective equipment in the fire service. As pulmonary function is a robust to COVID-19 infection and severe COVID-19 Recent evidence also demonstrated that to can increase both ACE2 and TMPRSS2 in alveolar type 2 cells and due to firefighting might have a direct effect on COVID-19 but further research is Cardiovascular Risk Age cardiovascular health is by the prevalence of cardiovascular risk factors which can include age, sex, hypertension, and from that 9% of US firefighters are 60 years of age or Although a this of the fire service might have a more pronounced risk of COVID-19 infection than the general A recent observational study reported that age is one of the leading risk factors for infection and death due to Other studies have confirmed this that older individuals (≥65 years) have from to times higher risk of COVID-19 Cardiovascular Risk Sex suggests that males are more to a COVID-19 infection than with one study from the New York City area that males made up of the patients hospitalized with the SARS-CoV-2 A study in found that males made up of the patients on in the males were more in COVID-19 patients than in The in and COVID-19 infection is thought to be due to levels of between males and Specifically, TMPRSS2 expression has been shown to be by and androgen receptor which is a requirement for the transcription of et reported that related to androgen increased the odds of having troponin T levels induced cardiac by the et also found that free androgen associated with COVID-19 and severity in males, but not in among males who were for COVID-19, each standard deviation increase in free androgen increased the odds of a positive COVID-19 as as severe COVID-19 by The fire service is et reported that to of the US fire service is comprised of and more than half of US metropolitan departments have no women firefighters. Other that of firefighters and of firefighters are an occupational group by is most likely to be by the SARS-CoV-2, as higher androgen levels are found in Cardiovascular Risk Hypertension Hypertension is a risk factor of COVID-19 and CVD that is known to have a high prevalence the US fire service. Hypertension is reported to be one of the most common comorbidities related to COVID-19 infection. In et al found that hypertension was present in 56.6% of hospitalized COVID-19 patients the New York City A these that chronic hypertension, with other cardiovascular were more among patients than survivors (48% also suggests that hypertension is associated with COVID-19 and that individuals as have higher odds of from COVID-19 than a Research that approximately 20% to 30% of the entire fire service have recent study found that 46% of firefighters and 29% of females had blood pressure the of 1 or 2 Cardiovascular Risk Obesity As discussed obesity has been found to increase the risk of a COVID-19 infection. there is a high prevalence of obesity in the US fire service. have shown that obesity was present in of COVID-19 hospitalized Interestingly, work by et al a between age and body Thus, with pronounced obesity are at an increased risk of being infected with SARS-CoV-2. This is for the US fire as obesity is a major CVD risk factor found in firefighters. Obesity has also been found to increase the risk of coronary heart disease and links the mechanisms of vascular alterations to cardiac suggests that firefighters with high have vascular function and are at a greater risk for

COVID-19 vasculitis and novel vasculitis mimics.

Viral dynamics of SARS-CoV-2 across a spectrum of disease severity in COVID-19

ABSTRACTA comprehensive analysis and characterization of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection model that mimics non-severe and severe coronavirus disease 2019 (COVID-19) in humans is warranted for understating the virus and developing preventive and therapeutic agents. Here, we characterized the K18-hACE2 mouse model expressing human (h)ACE2 in mice, controlled by the human keratin 18 (K18) promoter, in the epithelia, including airway epithelial cells where SARS-CoV-2 infections typically start. We found that intranasal inoculation with higher viral doses (2 × 103 and 2 × 104 PFU) of SARS-CoV-2 caused lethality of all mice and severe damage of various organs, including lung, liver, and kidney, while lower doses (2 × 101 and 2 × 102 PFU) led to less severe tissue damage and some mice recovered from the infection. In this hACE2 mouse model, SARS-CoV-2 infection damaged multiple tissues, with a dose-dependent effect in most tissues. Similar damage was observed in postmortem samples from COVID-19 patients. Finally, the mice that recovered from infection with a low dose of virus survived rechallenge with a high dose of virus. Compared to other existing models, the K18-hACE2 model seems to be the most sensitive COVID-19 model reported to date. Our work expands the information available about this model to include analysis of multiple infectious doses and various tissues with comparison to human postmortem samples from COVID-19 patients. In conclusion, the K18-hACE2 mouse model recapitulates both severe and non-severe COVID-19 in humans being dose-dependent and can provide insight into disease progression and the efficacy of therapeutics for preventing or treating COVID-19.IMPORTANCE The pandemic of coronavirus disease 2019 (COVID-19) has reached nearly 240 million cases, caused nearly 5 million deaths worldwide as of October 2021, and has raised an urgent need for the development of novel drugs and therapeutics to prevent the spread and pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To achieve this goal, an animal model that recapitulates the features of human COVID-19 disease progress and pathogenesis is greatly needed. In this study, we have comprehensively characterized a mouse model of SARS-CoV-2 infection using K18-hACE2 transgenic mice. We infected the mice with low and high doses of SARS-CoV-2 to study the pathogenesis and survival in response to different infection patterns. Moreover, we compared the pathogenesis of the K18-hACE2 transgenic mice with that of the COVID-19 patients to show that this model could be a useful tool for the development of antiviral drugs and therapeutics.

Novel Coronavirus COVID-19: Current Evidence and Evolving Strategies.

Should children with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection receive antiviral therapy? If so, what should we give, to which children, and for what disease severity?Despite brisk scientific progress elucidating the biology and transmission of SARS-CoV-2, and numerous adult trials testing antiviral therapies, we may pass the formative stages of this pandemic without defining antiviral agents' appropriate role in pediatric management. We urgently need pediatric clinical trials to establish the efficacy, safety, and pharmacokinetics of the most promising experimental and repurposed coronavirus disease 2019 (COVID-19) therapies proposed to date.1Researchers of early reports show that pediatric SARS-CoV-2 infection tends to be mild but that some children develop severe disease.2 In these reports, researchers highlight differences between pediatric and adult COVID-19 and argue that risk/benefit calculations of therapies derived from adult trials cannot be readily extrapolated to children. Gaps in our knowledge of pediatric COVID-19 further complicate assessments of risk and benefit. To date, we have a limited understanding of viral kinetics or immune responses in children, what factors predispose some children to severe disease, or how these variables affect responses to therapies. We have equally limited comprehension of how SARS-CoV-2 affects children with primary immunodeficiencies, illnesses requiring immune-compromising therapies, or other complex conditions. Nonetheless, treatment planning for severe pediatric cases, even if they will be few, has spurred children's hospitals to develop algorithms that include antiviral agents, such as remdesivir, chloroquine (CQ), and hydroxychloroquine (HCQ). Pediatricians have been forced to make these consequential decisions about therapies in an evidence vacuum.The struggle to repurpose CQ and HCQ for pediatric COVID-19 provides a potent example of the need for controlled therapy trials in children. To date, reports of pediatric use of these agents for COVID-19 are limited to anecdote. Doses and durations are inferred from conflicting in vitro studies, regimens for other diseases, and unpublished, underpowered, and conflicting adult clinical studies.1 Although both drugs have been used for years in children, their efficacy in COVID-19 is not assured. Studies of CQ use to prevent viral infections in animal models have yielded mixed results, with some revealing similar or inferior virological, immunologic, and clinical outcomes compared with no therapy.3 In studies of CQ and HCQ to treat a range of viral infections in adults, researchers have failed to show benefit, despite encouraging in vitro data.4 Although many children's hospitals are already using CQ and HCQ for COVID-19, appropriate dosing, efficacy, and safety of these drugs in pediatric COVID-19 patients remain unknown.Equipoise over safety and effectiveness of antiviral agents like CQ and HCQ to treat COVID-19 has led to a wave of adult clinical trials. This development has been slow to take hold in pediatrics. In a preprint systematic review, researchers identified 63 trials of conventional therapy targeting COVID-19 in China, only 3 of which enrolled patients <16 years old.5 As of April 18, 2020, clinicaltrials.gov listed 26 conventional therapy trials that do not exclude children outright. All of these also recruit adults. As discussed below, combined pediatric–adult trials may be a strategy to gather drug efficacy data in children, but it is not clear that these existing trials will have sufficient power to analyze efficacy in children specifically. If researchers of trials continue to sideline children, we will ultimately be unable to tell if antiviral agents used to treat ill pediatric patients helped, harmed, or did nothing.In absence of a vaccine, antiviral agents have been proposed as a strategy to prevent SARS-CoV-2 infection. Because most children experience mild infection, pediatric prophylaxis theoretically would serve to reduce viral reservoirs and mitigate spread from children to individuals at higher risk for severe COVID-19. We must be confident that any treatment provided for this purpose is explicitly safe and effective in pediatric populations. Trials studying prophylaxis in children face a number of hurdles, such as challenges with measurement of secondary public health benefits of treating asymptomatic children. The pediatric community may decide that the ethical and scientific dilemmas inherent to preventive antiviral therapy supersede their potential utility. However, if antiviral agents do show promise in preventing SARS-CoV-2 infection, use in children should be predicated on robust pediatric trials.Admittedly, there may be several impediments to antiviral clinical trials in SARS-CoV-2–infected children. These include uncertainty over which outcomes to use (such as improvements in oxygenation, inflammation, or virological clearance) and concerns about low recruitment, given the typically mild course of pediatric infection and public misconceptions of antiviral agents' efficacy. Additionally, heterogeneity of conditions predisposing to severe disease may complicate trial analysis. Conducting trials during a pandemic also raises unique ethical challenges, such as balancing research versus clinical care and titrating tolerance of experimental therapies' risks to an evolving understanding of disease.To address these concerns and others, and to promote development of trial protocols, we offer 6 recommendations.As pediatric researchers and health care providers, we must decide if we will rigorously study drug efficacy for children with COVID-19, or administer these agents on the unproven hope that giving anything at all is better than giving supportive care alone. We know that COVID-19 follows a different course in children than adults, so we cannot rely on results that trickle down from adult trials. Conducting controlled, coordinated pediatric trials is the only way to learn whether the potential benefits of these drugs outweigh their risks. The urgency with which we pursue robust studies now will determine if we know what to do, or if we will continue to guess, should this pandemic persist.We thank Dr Amy Sherman for her insights on this Perspective.

The emergence and rapid global spread of the coronavirus disease 2019 (COVID-19) has presented a significant global health challenge. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects human host cells through the interaction of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), which serve as main regulators for viral entry. Specifically, ACE2 and TMPRSS2 genes are influenced by two microRNAs: miR-200b-3p and miR-214-3p, respectively. The objective of this study was to explore the association between the serum levels of miR-200b-3p and miR-214-3p and the presence of circulating ACE2 and TMPRSS2 in severe and non-severe cases of COVID-19. This study sought to examine the potential utility of microRNAs as biomarkers for assessing disease severity and progression. Additionally, the study aimed to elucidate the interplay between microRNAs and the ACE2 and TMPRSS2 proteins, which play crucial roles in facilitating SARS-CoV-2 viral entry and infection. This practical-foundational study involved the collection of samples from 61 hospitalized patients with confirmed COVID-19 and 31 healthy individuals. Subsequently, the enzyme-linked immunosorbent assay (ELISA) technique was utilized to measure the concentrations of ACE2 and TMPRSS2 in the blood samples. Additionally, the expression levels of serum miR-200b-3p and miR-214-3p were analyzed using real-time polymerase chain reaction (PCR). The statistical analysis of the data was conducted using GraphPad Prism software (version 8.02) and SPSS software (version 19.0), ensuring the accurate interpretation of results. The findings revealed significant increases in the peripheral blood concentrations of ACE2 and TMPRSS2 in patients with non-severe COVID-19, compared to healthy individuals (P < 0.001 and P < 0.01, respectively). Similarly, patients with severe COVID-19 exhibited higher serum levels of ACE2 and TMPRSS2 than healthy subjects (P < 0.0001). Additionally, the serum levels of miR-200b-3p and miR-214-3p were decreased in both non-severe and severe COVID-19 patients, compared to healthy individuals (P < 0.01 and P < 0.0001, respectively). Moreover, a decrease in the serum levels of both miR-200b-3p and miR-214-3p was observed in patients with severe COVID-19, compared to those with non-severe cases (P < 0.001). Furthermore, this study identified a negative correlation between miR-200b-3p and ACE2 serum levels and between miR-214-3p and TMPRSS2 peripheral blood levels. The above-mentioned findings suggest that miR-200b-3p and miR-214-3p might be potential biomarkers for disease severity and prognosis in COVID-19 patients.

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