COVID-19 immune features revealed by a large-scale single-cell transcriptome atlas.

A dysfunctional immune response in coronavirus disease 2019 (COVID-19) patients is a recurrent theme impacting symptoms and mortality, yet a detailed understanding of pertinent immune cells is not complete. We applied single-cell RNA sequencing to 284 samples from 196 COVID-19 patients and controls and created a comprehensive immune landscape with 1.46 million cells. The large dataset enabled us to identify that different peripheral immune subtype changes are associated with distinct clinical features, including age, sex, severity, and disease stages of COVID-19. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA was found in diverse epithelial and immune cell types, accompanied by dramatic transcriptomic changes within virus-positive cells. Systemic upregulation of S100A8/A9, mainly by megakaryocytes and monocytes in the peripheral blood, may contribute to the cytokine storms frequently observed in severe patients. Our data provide a rich resource for understanding the pathogenesis of and developing effective therapeutic strategies for COVID-19.

High titers of neutralizing antibodies in the blood fail to eliminate SARS-CoV-2 viral RNA in the upper respiratory tract.

Retest-positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA, as a unique phenomenon among discharged individuals, has been demonstrated to be safe in the community. Still, the underlying mechanism of viral lingering is less investigated. In this study, first, we find that the frequency of viral RNA-positive retesting differs among variants. Higher ratios of viral RNA-positive retest were more frequently observed among Delta (61.41%, 514 of 837 cases) and Omicron (39.53%, 119 of 301 cases) infections than among ancestral viral infection (7.27%, 21 of 289 cases). Second, the tissues where viral RNA reoccurred were altered. Delta RNA reoccurred mainly in the upper respiratory tract (90%), but ancestral virus RNA reoccurred mainly in the gastrointestinal tract (71%). Third, vaccination did not reduce the frequency of viral RNA-positive retests, despite high concentrations of viral-specific antibodies in the blood. Finally, 37 of 55 (67.27%) Delta-infected patients receiving neutralizing antibody therapy become viral RNA retest positive when high concentrations of neutralizing antibodies still patrol in the blood. Altogether, our findings suggest that the presentence of high titers of neutralizing antibodies in the blood is incompetent in clearing residual viral RNA in the upper respiratory tract.

Metabolomic analyses reveal new stage-specific features of COVID-19.

The current pandemic of coronavirus disease 2019 (COVID-19) has affected >160 million individuals to date, and has caused millions of deaths worldwide, at least in part due to the unclarified pathophysiology of this disease. Identifying the underlying molecular mechanisms of COVID-19 is critical to overcome this pandemic. Metabolites mirror the disease progression of an individual and can provide extensive insights into their pathophysiological significance at each stage of disease. We provide a comprehensive view of metabolic characterisation of sera from COVID-19 patients at all stages using untargeted and targeted metabolomic analysis. As compared with the healthy controls, we observed different alteration patterns of circulating metabolites from the mild, severe and recovery stages, in both the discovery cohort and the validation cohort, which suggests that metabolic reprogramming of glucose metabolism and the urea cycle are potential pathological mechanisms for COVID-19 progression. Our findings suggest that targeting glucose metabolism and the urea cycle may be a viable approach to fight COVID-19 at various stages along the disease course.

Prognostic roles of KL-6 in disease severity and lung injury in COVID-19 patients: A longitudinal retrospective analysis.

To investigate the dynamic changes of Krebs von den Lungen-6 (KL-6) among patients with coronavirus disease 2019 (COVID-19) and the role of KL-6 as a noninvasive biomarker for predicting long-term lung injury, the clinical information and laboratory tests of 166 COVID-19 patients were collected, and a correlation analysis between KL-6 and other parameters was conducted. There were 17 (10.2%, 17/166) severe/critical and 149 (89.8%, 149/166) mild COVID-19 patients in our cohort. Serum KL-6 was significantly higher in severe/critical COVID-19 patients than in mild patients (median 898.0 vs. 451.2 U/ml, p < .001). KL-6 was next confirmed to be a sensitive and specific biomarker for distinguishing mild and severe/critical patients and correlate to computed tomography lung lesions areas. Serum KL-6 concentration during the follow-up period (>100 days postonset) was well correlated to those concentrations within 10 days postonset (Pearson r = .867, p < .001), indicating the prognostic value of KL-6 levels in predicting lung injury after discharge. Finally, elevated KL-6 was found to be significantly correlated to coagulation disorders, and T cells subsets dysfunctions. In summary, serum KL-6 is a biomarker for assessing COVID-19 severity and predicting the prognosis of lung injury of discharged patients.

Immunopathological characteristics of coronavirus disease 2019 cases in Guangzhou, China.

Coronavirus disease 2019 (COVID-19) is a respiratory disorder caused by the highly contagious severe acute respiratory syndrome coronavirus 2. The immunopathological characteristics of patients with COVID-19, either systemic or local, have not been thoroughly studied. In the present study, we analysed both the changes in the number of various immune cell types as well as cytokines important for immune reactions and inflammation. Our data indicate that patients with severe COVID-19 exhibited an overall decline of lymphocytes including CD4+ and CD8+ T cells, B cells and natural killer cells. The number of immunosuppressive regulatory T cells was moderately increased in patients with mild COVID-19. Interleukin-6 (IL-6), IL-10 and C-reactive protein were remarkably up-regulated in patients with severe COVID-19. In conclusion, our study shows that the comprehensive decrease of lymphocytes, and the elevation of IL-6, IL-10 and C-reactive protein are reliable indicators of severe COVID-19.

Hypoproteinemia is an independent risk factor for the prognosis of severe COVID-19 patients.

Severe patients of the coronavirus disease 2019 (COVID-19) may progress rapidly to critical stage. This study aimed to identify factors useful for predicting the progress. 33 severe COVID-19 patients at the intensive care unit were included in this study. During treatment, 13 patients deteriorated and required further treatment for supporting organ function. The remaining 20 patients alleviated and were transferred to the general wards. The multivariate COX regression analyses showed that hypoproteinemia was an independent risk factor associated with deterioration of severe patients (HR, 0.763; 95% CI, 0.596 to 0.978; p = 0.033). The restricted cubic spline indicated that when HR = 1, the corresponding value of albumin is 29.6 g/L. We used the cutoff of 29.6 g/L to divide these patients. Kaplan-Meier curves showed that the survival rate of the high-albumin group was higher than that of the low-albumin group. Therefore, hypoalbuminemia may be an independent risk factor to evaluate poor prognosis of severely patients with COVID-19, especially when albumin levels were below 29.6 g/L.

Effects of products designed to modulate the gut microbiota on hyperlipidaemia.

PURPOSE: Fatalities due to heart and cerebrovascular diseases caused by uncontrolled hyperlipidaemia increase every year; on the other hand, lipid-lowering drugs are known to cause side effects. The gut microbiota has been thoroughly investigated by researchers and consumers, because they have unique functional properties and littler side effects. However, the effects of the gut microbiota remain controversial. We conducted a meta-analysis to assess the effects of products designed to modulate the gut microbiota on various hyperlipidaemias. METHODS: We systematically searched PubMed, Embase, Cochrane Library (Central), and Web of Science for randomized controlled trials (published before June 2017, and those only in English) to compare treatment (products designed to modulate the gut microbiota) versus placebo. Our main endpoints were total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) in serum. We assessed pooled data using a fixed effects model. RESULTS: Of 1337 identified studies, 21 were eligible and included in our analysis (n = 1436 participants). The combined estimate of effect size for the impact of products designed to modulate the gut microbiota on serum TC (WMD - 11.07 mg/dL, 95% CI - 13.72 to - 8.43, p < 0.001), LDL-C (WMD - 10.96 mg/dL, 95% CI - 13.37 to - 8.56, p < 0.001), and HDL-C (WMD 0.72 mg/dL, 95% CI 0.06-1.38, p = 0.032) were statistically significant, while no significant effect was found on TG concentrations (WMD - 0.56 mg/dL, 95% CI - 5.59 to 4.47, p = 0.828). Subgroup analysis showed parallel trials, probiotics, and long-term intervention had better effects on lowering blood lipid levels. CONCLUSION: Products designed to modulate the gut microbiota results in changes of the plasma lipid concentrations and these changes may protect against cardiovascular disease.

Factors Associated With Prolonged Viral Shedding in Patients With Avian Influenza A(H7N9) Virus Infection.

Background: Data are limited on the impact of neuraminidase inhibitor (NAI) treatment on avian influenza A(H7N9) virus RNA shedding. Methods: In this multicenter, retrospective study, data were collected from adults hospitalized with A(H7N9) infection during 2013-2017 in China. We compared clinical features and A(H7N9) shedding among patients with different NAI doses and combination therapies and evaluated factors associated with A(H7N9) shedding, using Cox proportional hazards regression. Results: Among 478 patients, the median age was 56 years, 71% were male, and 37% died. The median time from illness onset to NAI treatment initiation was 8 days (interquartile range [IQR], 6-10 days), and the median duration of A(H7N9) RNA detection from onset was 15.5 days (IQR, 12-20 days). A(H7N9) RNA shedding was shorter in survivors than in patients who died (P < .001). Corticosteroid administration (hazard ratio [HR], 0.62 [95% confidence interval {CI}, .50-.77]) and delayed NAI treatment (HR, 0.90 [95% CI, .91-.96]) were independent risk factors for prolonged A(H7N9) shedding. There was no significant difference in A(H7N9) shedding duration between NAI combination treatment and monotherapy (P = .65) or between standard-dose and double-dose oseltamivir treatment (P = .70). Conclusions: Corticosteroid therapy and delayed NAI treatment were associated with prolonged A(H7N9) RNA shedding. NAI combination therapy and double-dose oseltamivir treatment were not associated with a reduced A(H7N9) shedding duration as compared to standard-dose oseltamivir.

The Protective Effects of the A/ZJU01/ PR8/2013 Split H7N9 Avian Influenza Vaccine Against Highly Pathogenic H7N9 in BALB/c Mice.

BACKGROUND/AIMS: Since the first case of novel H7N9 infection was reported, China has experienced five epidemics of H7N9. During the fifth wave, a highly pathogenic H7N9 strain emerged. In order to assess whether the H7N9 vaccine based on A/Zhejiang/DTID-ZJU01/2013(H7N9) was effective in protecting against highly pathogenic H7N9, we conducted this study. METHODS: Groups of mice were immunized twice by intraperitoneal injection with 500 µl of either split vaccine alone or MF59-adjuvanted vaccine. Serum was collected 2 weeks after the second vaccine booster. The hemagglutinin inhibition test was conducted on vaccine seed and highly pathogenic H7N9 to evaluate the neutralization of highly pathogenic H7N9. We also immunized mice and challenged them with highly pathogenic H7N9. Mice were observed for illness, weight loss, and death at 1 week and 2 weeks post-infection. Then, the mice were sacrificed and lungs were removed. Antibody responses were assessed and pathological changes in the lung tissue were evaluated. RESULTS: The ability of serum to neutralize highly pathogenic H7N9 was reduced. In mice, highly pathogenic H7N9 was more virulent than A/Zhejiang/DTID-ZJU01/2013(H7N9). After challenge with highly pathogenic H7N9, all mice died while mice challenged with A/Zhejiang/DTID-ZJU01/2013(H7N9) all recovered. The A/ZJU01/PR8/2013 split H7N9 avian influenza vaccine was able to protect against infection with highly pathogenic H7N9 in mice, with or without MF59. Moreover, H7N9 vaccine adjuvanted with MF59 produced high antibody levels, which lead to better protection. CONCLUSIONS: The A/ZJU01/PR8/2013 split H7N9 avian influenza vaccine based on A/Zhejiang/DTID-ZJU01/2013(H7N9) is effective in protecting against highly pathogenic H7N9. H7N9 vaccine adjuvanted with MF59 offers better protection against infection with highly pathogenic H7N9. In order to make the H7N9 vaccine applicable to humans, further clinical trials are required to evaluate MF59 adjuvanted vaccine. Meanwhile, the vaccine strain should be updated based on the highly pathogenic H7N9 gene sequence.

Adjuvant Corticosteroid Treatment in Adults With Influenza A (H7N9) Viral Pneumonia.

OBJECTIVE: To determine the impact of adjuvant corticosteroids administered to patients hospitalized with influenza A (H7N9) viral pneumonia. DESIGN: The effects of adjuvant corticosteroids on mortality were assessed using multivariate Cox regression and a propensity score-matched case-control study. Nosocomial infections and viral shedding were also compared. SETTING: Hospitals with influenza A (H7N9) viral pneumonia patient admission in 84 cities and 16 provinces of Mainland China. PATIENTS: Adolescent and Adult patients aged >14 yr with severe laboratory-confirmed influenza A (H7N9) virus infections were screened from April 2013 to March 2015. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The study population comprised 288 cases who were hospitalized with influenza A (H7N9) viral pneumonia. The median age of the study population was 58 years, 69.8% of the cohort comprised male patients, and 51.4% had at least one type of underlying diseases. The in-hospital mortality was 31.9%. Two hundred and four patients (70.8%) received adjuvant corticosteroids; among them, 193 had hypoxemia and lung infiltrates, 11 had chronic obstructive pulmonary disease, and 11 had pneumonia only. Corticosteroids were initiated within 7 days (interquartile range, 5.0-9.4 d) of the onset of illness and the maximum dose administered was equivalent to 80-mg methylprednisolone (interquartile range, 40-120 mg). The patients were treated with corticosteroids for a median duration of 7 days (interquartile range, 4.0-11.3 d). Cox regression analysis showed that compared with the patients who did not receive corticosteroid, those who received corticosteroid had a significantly higher 60-day mortality (adjusted hazards ratio, 1.98; 95% CI, 1.03-3.79; p = 0.04). Subgroup analysis showed that high-dose corticosteroid therapy (> 150 mg/d methylprednisolone or equivalent) significantly increased both 30-day and 60-day mortality, whereas no significant impact was observed for low-to-moderate doses of corticosteroids (25-150 mg/d methylprednisolone or equivalent). The propensity score-matched case-control analysis showed that the median viral shedding time was much longer in the group that received high-dose corticosteroids (15 d), compared with patients who did not receive corticosteroids (13 d; p = 0.039). CONCLUSIONS: High-dose corticosteroids were associated with increased mortality and longer viral shedding in patients with influenza A (H7N9) viral pneumonia.

Mutational analysis of Pneumocystis jirovecii dihydropteroate synthase and dihydrofolate reductase genes in HIV-infected patients in China.

We investigated Pneumocystis jirovecii dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) genes for mutations in 25 Chinese HIV-infected patients with P. jirovecii pneumonia. We identified DHPS mutations in 3 (12%) patients and DHFR mutations in 1 (4%) patient. The prevalence of DHPS and DHFR mutations in China remains low, as it does in other developing countries.

[Preparation and quality evaluation of tanshinone IIA microemulsion for parenteral injection].

OBJECTIVE: To study the prescription and preparation technology of tanshinone IIA microemulsion for parenteral injection, and to evaluate its quality. METHODS: The prescription was selected and optimized through single-factor test, compatibility experiment and the pseudo-ternary phase diagram method. The preparation technology was investigated, and the droplet morphous, particle diameter, zeta potential, stability and haemolyticus were evaluated. RESULTS: The prescription composition of tanshinone IIA microemulsion was MCT:Solutol HS-15: fabaceous lecithin: absolute alcohol = 9:10:5:6(m/m), oil phase: aqueous phase = 1:10, with the drug-loaded of 1. 0 mg/g. The acquired microemulsion exhibited salmon pink,uniform and transparent, with the average particle diameter of 16. 04 nm, Zeta potential of -11. 57 mV, and the encapsulation efficiency of 98. 53%. The stability result showed that tanshinone IIA content in microemulsion was influenced by high temperature and illumination, indicating tanshinone IIA microemulsion should to be stored at low temperature and protected from light. The preparation was without hemolytic crisis. CONCLUSION: The preparation of tanshinone IIA micro- emulsion is simple,corresponding to the main index of parenteral injection and offering the basis for new dosage form development of tanshinone IIA.

Diverse immune responses in vaccinated individuals with and without symptoms after omicron exposure during the recent outbreak in Guangzhou, China.

Objectives: During the recent wave of coronavirus disease 2019 (COVID-19) infections in China, most individuals have been vaccinated and exposed to the omicron variant. In the present study, two cohorts were observed in the vaccinated population: vaccinated individuals with symptoms (VIWS) and those without symptoms (VIWOS). Our study aimed to characterize the antibody response in two cohorts: VIWS and VIWOS. Methods: A questionnaire survey was conducted in the community. Blood and saliva samples were collected from 124 individuals in the VIWS and VIWOS cohorts. Capture enzyme-linked immunosorbent assay (ELISA) was performed to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific antibodies. Results: The questionnaire survey revealed that 30.0 % (302/1005) of individuals in the older adult group (≥65 years) experienced no symptoms, whereas the rate of individuals without symptoms in the younger group (<65 years) was 17.8 % (166/932). Nucleocapsid (N)-specific IgM (N-IgM) was detected in the blood samples at a rate of 69.2 % (54/78) in the VIWS cohort. The positivity rate for N-specific IgA (N-IgA) was 93.6 % (73/78). In addition, the positivity rates of spike (S)-specific IgA (S-IgA) and N-IgA detected in saliva samples were 42 % (21/50) and 54 % (27/50), respectively. Both N-IgA positivity and negativity were observed in the VIWOS cohort. The detection rate of N-IgM positivity was 57.1 % (12/21) in the N-IgA-positive group. In addition, 54.3 % (25/46) of the vaccinated individuals without symptoms were IgA-negative. Conclusions: Our study indicates that substantial N-specific antibodies were induced during omicron infection and that testing for N-IgA in both blood and saliva may aid in the diagnosis of SARS-CoV-2 infection in vaccinated populations.

More attention should be paid to Omicron-associated sepsis: a multicenter retrospective study in south China.

Background: The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly transmissible but causes less severe disease compared to other variants. However, its association with sepsis incidence and outcomes is unclear. This study aimed to investigate the incidence of Omicron-associated sepsis, as per the Sepsis 3.0 definition, in hospitalized patients, and to explore its relationship with clinical characteristics and prognosis. Methods: This multicenter retrospective study included adults hospitalized with confirmed SARS-CoV-2 infection across six tertiary hospitals in Guangzhou, China from November 2022 to January 2023. The Sequential Organ Failure Assessment (SOFA) score and its components were calculated at hospital admission to identify sepsis. Outcomes assessed were need for intensive care unit (ICU) transfer and mortality. Receiver operating characteristic curves evaluated the predictive value of sepsis versus other biomarkers for outcomes. Results: A total of 299 patients (mean age: 70.1±14.4 years, 42.14% female) with SOFA score were enrolled. Among them, 152 were categorized as non-serious cases while the others were assigned as the serious group. The proportion of male patients, unvaccinated patients, patients with comorbidity such as diabetes, chronic cardiovascular disease, and chronic lung disease was significantly higher in the serious than non-serious group. The median SOFA score of all enrolled patients was 1 (interquartile range, 0-18). In our study, 147 patients (64.19%) were identified as having sepsis upon hospital admission, with the majority of these septic patients (113, representing 76.87%) being in the serious group, the respiratory, coagulation, cardiovascular, central nervous, and renal organ SOFA scores were all significantly higher in the serious compared to the non-serious group. Among septic patients, 20 out of 49 (40.81%) had septic shock as indicated by lactate measurement within 24 hours of admission, and the majority of septic patients were in the serious group (17/20, 76.87%). Sepsis was present in 118 out of 269 (43.9%) patients in the general ward, and among those with sepsis, 34 out of 118 (28.8%) later required ICU care during hospitalization. By contrast, none of the patients without sepsis required ICU care. Moreover, the mortality rate was significantly higher in patients with than without sepsis. Conclusions: A considerable proportion of patients infected with Omicron present with sepsis upon hospital admission, which is associated with a poorer prognosis. Therefore, early recognition of viral sepsis by evaluation of the SOFA score in hospitalized coronavirus disease 2019 patients is crucial.

Gut microbial co-metabolite 2-methylbutyrylcarnitine exacerbates thrombosis via binding to and activating integrin α2ß1.

Thrombosis represents the leading cause of death and disability upon major adverse cardiovascular events (MACEs). Numerous pathological conditions such as COVID-19 and metabolic disorders can lead to a heightened thrombotic risk; however, the underlying mechanisms remain poorly understood. Our study illustrates that 2-methylbutyrylcarnitine (2MBC), a branched-chain acylcarnitine, is accumulated in patients with COVID-19 and in patients with MACEs. 2MBC enhances platelet hyperreactivity and thrombus formation in mice. Mechanistically, 2MBC binds to integrin α2ß1 in platelets, potentiating cytosolic phospholipase A2 (cPLA2) activation and platelet hyperresponsiveness. Genetic depletion or pharmacological inhibition of integrin α2ß1 largely reverses the pro-thrombotic effects of 2MBC. Notably, 2MBC can be generated in a gut-microbiota-dependent manner, whereas the accumulation of plasma 2MBC and its thrombosis-aggravating effect are largely ameliorated following antibiotic-induced microbial depletion. Our study implicates 2MBC as a metabolite that links gut microbiota dysbiosis to elevated thrombotic risk, providing mechanistic insight and a potential therapeutic strategy for thrombosis.

Effect of the Timing of Amubarvimab/Romlusevimab (BRII-196/198) Administration on Progression to Severe Disease in Elderly Patients with COVID-19 Infection: A Retrospective Cohort Study.

Objective: Early intervention with neutralizing antibodies is considered to be effective in preventing disease progression in patients with mild to moderate COVID-19 infection. Elderly patients are the most susceptible and at a higher risk of COVID-19 infection. The present study aimed to assess the necessity and possible clinical benefits of the early administration of Amubarvimab/Romlusevimab (BRII-196/198) in the elderly population. Methods: The present study was designed as a retrospective, multi-center cohort study conducted with 90 COVID-19 patients aged over 60, who were divided into two groups based on the timing of the administration of BRII-196/198 (administration at ≤ 3 days or > 3 days from the onset of infection symptoms). Results: The ≤ 3 days group exhibited a greater positive effect (HR 5.94, 95% CI, 1.42-24.83; P < 0.01), with only 2 patients among 21 patients (9.52%) exhibiting disease progression, compared to the 31 patients among the 69 patients (44.93%) of the > 3 days group who exhibited disease progression. The multivariate Cox regression analysis revealed low flow oxygen support prior to BRII-196/198 administration (HR 3.53, 95% CI 1.42-8.77, P < 0.01) and PLT class (HR 3.68, 95% CI 1.37-9.91, P < 0.01) as independent predictors of disease progression. Conclusions: In elderly patients with mild or moderate COVID-19 disease, who do not require oxygen support and had the risk factors for disease progression to severe COVID-19 disease, the administration of BRII-196/198 within 3 days resulted in a beneficial trend in terms of preventing disease progression.

Venovenous extracorporeal membrane oxygenation for COVID-19 and influenza H1N1 associated acute respiratory distress syndrome: A comparative cohort study in China.

Background: Venovenous extracorporeal membrane oxygenation (VV-ECMO) has been demonstrated to be effective in treating patients with virus-induced acute respiratory distress syndrome (ARDS). However, whether the management of ECMO is different in treating H1N1 influenza and coronavirus disease 2019 (COVID-19)-associated ARDS patients remains unknown. Methods: This is a retrospective cohort study. We included 12 VV-ECMO-supported COVID-19 patients admitted to The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Eighth People's Hospital, and Wuhan Union Hospital West Campus between January 23 and March 31, 2020. We retrospectively included VV-ECMO-supported patients with COVID-19 and H1N1 influenza-associated ARDS. Clinical characteristics, respiratory mechanics including plateau pressure, driving pressure, mechanical power, ventilatory ratio (VR) and lung compliance, and outcomes were compared. Results: Data from 25 patients with COVID-19 (n=12) and H1N1 (n=13) associated ARDS who had received ECMO support were analyzed. COVID-19 patients were older than H1N1 influenza patients (P=0.004). The partial pressure of arterial carbon dioxide (PaCO2) and VR before ECMO initiation were significantly higher in COVID-19 patients than in H1N1 influenza patients (P <0.001 and P=0.004, respectively). COVID-19 patients showed increased plateau and driving pressure compared with H1N1 subjects (P=0.013 and P=0.018, respectively). Patients with COVID-19 remained longer on ECMO support than did H1N1 influenza patients (P=0.015). COVID-19 patients who required ECMO support also had fewer intensive care unit and ventilator-free days than H1N1. Conclusions: Compared with H1N1 influenza patients, COVID-19 patients were older and presented with increased PaCO2 and VR values before ECMO initiation. The differences between ARDS patients with COVID-19 and influenza on VV-ECMO detailed herein could be helpful for obtaining a better understanding of COVID-19 and for better clinical management.