Blood Eosinophils Matter in Post-COVID-19 Pneumonia.

BACKGROUND: Even after the development of vaccines, SARS-CoV-2 continues to cause severe pneumonia all over the world. Consequently, in order to improve the management of patients and optimize the use of resources, predictors of disease severity and lung complications after COVID-19 pneumonia are urgently needed. Blood cell count is an easily available and reproducible biomarker. With this study, we aimed to explore the role of eosinophils in predicting disease behavior and pulmonary sequelae at first follow-up with computed tomography (CT). METHODS: we evaluated blood cell count and other inflammatory markers, both at baseline and during hospitalization, in a large population of hospitalized COVID-19 patients. RESULTS: 327 patients were finally enrolled, 214 were classified as low-intensity medical care (LIMC) and 113 as high-intensity medical care. Eosinophils were higher at discharge in the HIMC group [0.1 (0-0.72) vs. 0.05 (0-0.34) × 109/L; p < 0.0001]. Moreover, in the multivariable analysis, age ≥ 62 years (OR 1.76 (1.05-2.8) p = 0.03) and Δ eosinophils ≥ 0.05 (OR 1.75 (1.05-2.9) p = 0.03) were two independent predictors of residual lung abnormalities in the whole patient population at first follow-up. CONCLUSIONS: an eosinophil increase during hospitalization could be a potential predictor of pulmonary sequelae in surviving patients after COVID-19 pneumonia.

Interstitial lung disease with and without progressive fibrosing phenotype in patients with idiopathic inflammatory myopathies: data from a large multicentric cohort.

OBJECTIVES: Patients with connective tissue diseases can develop interstitial lung disease (ILD), leading to a progressive fibrosing ILD (PF-ILD) phenotype in some cases. We aimed to investigate the occurrence of PF-ILD in idiopathic inflammatory myopathies (IIMs), and factors potentially predicting this phenotype. Secondary aims were to assess the radiological pattern and factors associated with IIMs-ILD. METHODS: Patients with IIMs from our multicentric prospective cohort were retrospectively evaluated. Data were recorded at IIMs and ILD diagnosis, and during follow-up. Patients with ILD were classified according to the predominant high-resolution CT (HRCT) pattern: non-specific interstitial pneumonia (NSIP), usual interstitial pneumonia (UIP) and organising pneumonia (OP). PF-ILD was defined according to the 2022 American Thoracic Society (ATS), European Respiratory Society (ERS), Japanese Respiratory Society (JRS) and Latin American Thoracic Society (ALAT) guidelines. Univariate and multivariate analyses were performed to identify factors associated to ILD and to PF-ILD. RESULTS: Of 253 patients with IIMs, 125 (49%) had ILD: 99 (78%) at IIMs diagnosis and 26 (22%) during follow-up (21/26 within 5 years). Multivariate analysis identified anti-Jo-1, anti-MDA5, anti-Ro52, high score on manual muscle test, mechanic's hands and Raynaud's phenomenon as independently associated with ILD. The predominant HRCT pattern was NSIP (50% of patients), followed by UIP (28%) and OP (22%). At 1-year follow-up, PF-ILD occurred in 18% of IIMs-ILD. PF-ILD was predicted by anti-MDA5, heliotropic rash, xerostomia and xerophthalmia at univariate but not at multivariate analysis. CONCLUSION: Patients with IIM should be carefully screened for ILD at IIMs diagnosis and yearly during follow-up. All patients with IIMs-ILD should be carefully monitored to capture ILD progression since a consistent proportion of them are expected to develop PF-ILD.

Molecular Mechanism in the Development of Pulmonary Fibrosis in Patients with Sarcoidosis.

Sarcoidosis is a multisystemic disease of unknown etiology characterized by the formation of granulomas in various organs, especially lung and mediastinal hilar lymph nodes. The clinical course and manifestations are unpredictable: spontaneous remission can occur in approximately two thirds of patients; up to 20% of patients have chronic course of the lung disease (called advanced pulmonary sarcoidosis, APS) resulting in progressive loss of lung function, sometimes life-threatening that can lead to respiratory failure and death. The immunopathology mechanism leading from granuloma formation to the fibrosis in APS still remains elusive. Recent studies have provided new insights into the genetic factors and immune components involved in the clinical manifestation of the disease. In this review we aim to summarize the clinical-prognostic characteristics and molecular pathways which are believed to be associated with the development of APS.

Prevalence of diaphragm dysfunction in patients with interstitial lung disease (ILD): The role of diaphragmatic ultrasound.

BACKGROUND: Diaphragm ultrasound (DUS) has been extensively used in critically ill patients while data on outpatients with interstitial lung disease (ILD) are limited. We hypothesized that diaphragm function, assessed by ultrasound, could be impaired in patients with ILD, considering both Idiopathic Pulmonary Fibrosis (IPF) and Connective Tissue Disease (CTD-ILD), compared to healthy subjects. Moreover, this impairment could impact clinical and functional parameters. METHODS: All consecutive CTD-ILD and IPF patients followed in our center (March-October 2020) were screened. Diaphragm displacement (DD), inspiratory thickness (Ti), expiratory thickness (Te), thickening fraction (TF), and respiratory functional parameters were collected. The prevalence of diaphragmatic dysfunction (TF <30%) was then recorded. RESULTS: Eighty-two consecutive patients (41 CTD-ILD, 41 IPF) and 15 age- and sex-matched controls were enrolled. In the overall population, 24 out of 82 (29%) presented diaphragmatic dysfunction. In CTD-ILD, DD and Ti were lower as compared to IPF (p = 0.021 and p = 0.036, respectively); while diaphragmatic dysfunction was more prevalent compared to controls (37% vs 7%, p = 0.043). TF positively correlated to patients' functional parameters in the CTD-ILD group (FVC%pred: p = 0.003; r = 0.45), while not in the IPF group. Diaphragmatic dysfunction was associated with moderate/severe dyspnea in both CTD-ILD and IPF (p = 0.021). CONCLUSION: The prevalence of diaphragmatic dysfunction was 29% in patients with ILD and was associated with moderate/severe dyspnea. CTD-ILD presented lower DD compared with IPF and a higher prevalence of diaphragmatic dysfunction (TF<30%) compared with controls. TF was associated with lung function only in CTD-ILD patients, suggesting its potential role in the comprehensive patient assessment.

Predictors of pulmonary sequelae after COVID-19 pneumonia: A 12-month follow-up study.

Background: Since the beginning of the SARS-CoV-2 pandemic, over 550 million people have been infected worldwide. Despite these large numbers, the long-term pulmonary consequences of COVID-19 remain unclear. Aims: The aim of this single-center observational cohort study was to identify and characterize pulmonary sequelae of COVID-19 at 12 months from hospitalization and to reveal possible predictors for the persistence of long-term lung consequences. Methods: Based on the persistence or absence of radiological changes after 12 months from hospitalization, the whole population was categorized into NOT-RECOVERED (NOT-REC) and RECOVERED (REC) groups, respectively. Clinical and pulmonary function data tests and clinical data were also collected and compared in the two groups. In the NOT-REC group, high resolution computed tomography (HRCT) images were semiquantitatively scored analyzing ground-glass opacities (GGO), interstitial thickening (IT), consolidations (CO), linear and curvilinear band opacities, and bronchiectasis for each lung lobe. Logistic regression analyses served to detect the factors associated with 12-month radiological consequences. Results: Out of the 421 patients followed after hospitalization for SARS-CoV-2 pneumonia, 347 met inclusion and exclusion criteria and were enrolled in the study. The NOT-REC patients (n = 24; 6.9%) were significantly older [67 (62-76) years vs. 63 (53-71) years; p = 0.02], more frequently current smokers [4 (17%) vs. 12 (4%); p = 0.02], and with more severe respiratory failure at the time of hospitalization [PaO2/FiO2 at admission: 201 (101-314) vs. 295 (223-343); p = 0.01] compared to REC group (n = 323; 93.1%). On multivariable analysis, being a current smoker resulted in an independent predictor for lung sequelae after 12 months from hospitalization [5.6 OR; 95% CI (1.41-22.12); p = 0.01]. Conclusion: After 12 months from hospital admission, a limited number of patients displayed persistent pulmonary sequelae with minimal extension. Being a current smoker at the time of SARS-CoV-2 infection is an independent predictive factor to lung consequences, regardless of the disease severity.

Radiological Assessment in Idiopathic Pulmonary Fibrosis (IPF) Patients According to MUC5B Polymorphism.

The MUC5B rs35705950 mutant T allele is the strongest genetic risk factor for familial and sporadic IPF. We sought to determine whether MUC5B genotype influences radiological patterns of IPF at diagnosis, as well as their change over time, in patients on antifibrotic therapy. Among eighty-eight IPF patients, previously genotyped for MUC5B rs35705950, we considered seventy-eight patients who were evaluated for radiological quantification of the following features both at treatment initiation (HRCT1) and after 1 year (HRCT2): ground glass opacities (AS), reticulations (IS) and honeycombing (HC). Of the evaluated patients, 69% carried at least one copy of the T allele (TT/TG). Carriers of the T allele displayed similar FVC loss in the first year of treatment as GG carriers, but overall survival at the end of follow-up was longer in the TT/TG group, compared to the GG group. In the GG group, both the AS and HC increased significantly, whereas in the TT/TG group only HC increased over the first year of treatment. MUC5B rs35705950 GG carriers are associated with increased ground glass and honeycombing extent over time and worse survival than T allele carriers. Longitudinal HRCT may help define the prognostic role of the MUC5B rs35705950 genotype.

The role of immune response in the pathogenesis of idiopathic pulmonary fibrosis: far beyond the Th1/Th2 imbalance.

INTRODUCTION: Idiopathic pulmonary fibrosis (IPF) is a chronic disease of unknown origin characterized by progressive scarring of the lung leading to irreversible loss of function. Despite the availability of two drugs that are able to slow down disease progression, IPF remains a deadly disease. The pathogenesis of IPF is poorly understood, but a dysregulated wound healing response following recurrent alveolar epithelial injury is thought to be crucial. AREAS COVERED: In the last few years, the role of the immune system in IPF pathobiology has been reconsidered; indeed, recent data suggest that a dysfunctional immune system may promote and unfavorable interplay with pro-fibrotic pathways thus acting as a cofactor in disease development and progression. In this article, we review and critically discuss the role of T cells in the pathogenesis and progression of IPF in the attempt to highlight ways in which further research in this area may enable the development of targeted immunomodulatory therapies for this dreadful disease. EXPERT OPINION: A better understanding of T cell interactions has the potential to facilitate the development of immune modulators targeting multiple T cell-mediated pathways, thus halting disease initiation and progression.

Neutralising reactivity against SARS-CoV-2 Delta and Omicron variants by vaccination and infection history.

BACKGROUND: The continuous emergence of SARS-CoV-2 variants of concern (VOC) with immune escape properties, such as Delta (B.1.617.2) and Omicron (B.1.1.529), questions the extent of the antibody-mediated protection against the virus. Here we investigated the long-term antibody persistence in previously infected subjects and the extent of the antibody-mediated protection against B.1, B.1.617.2 and BA.1 variants in unvaccinated subjects previously infected, vaccinated naïve and vaccinated previously infected subjects. METHODS: Blood samples collected 15 months post-infection from unvaccinated (n=35) and vaccinated (n=41) previously infected subjects (Vo' cohort) were tested for the presence of antibodies against the SARS-CoV-2 spike (S) and nucleocapsid (N) antigens using the Abbott, DiaSorin, and Roche immunoassays. The serum neutralising reactivity was assessed against B.1, B.1.617.2 (Delta), and BA.1 (Omicron) SARS-CoV-2 strains through micro-neutralisation. The antibody titres were compared to those from previous timepoints, performed at 2- and 9-months post-infection on the same individuals. Two groups of naïve subjects were used as controls, one from the same cohort (unvaccinated n=29 and vaccinated n=20) and a group of vaccinated naïve healthcare workers (n=61). RESULTS: We report on the results of the third serosurvey run in the Vo' cohort. With respect to the 9-month time point, antibodies against the S antigen significantly decreased (P=0.0063) among unvaccinated subjects and increased (P<0.0001) in vaccinated individuals, whereas those against the N antigen decreased in the whole cohort. When compared with control groups (naïve Vo' inhabitants and naïve healthcare workers), vaccinated subjects that were previously infected had higher antibody levels (P<0.0001) than vaccinated naïve subjects. Two doses of vaccine elicited stronger anti-S antibody response than natural infection (P<0.0001). Finally, the neutralising reactivity of sera against B.1.617.2 and BA.1 was 4-fold and 16-fold lower than the reactivity observed against the original B.1 strain. CONCLUSIONS: These results confirm that vaccination induces strong antibody response in most individuals, and even stronger in previously infected subjects. Neutralising reactivity elicited by natural infection followed by vaccination is increasingly weakened by the recent emergence of VOCs. While immunity is not completely compromised, a change in vaccine development may be required going forward, to generate cross-protective pan-coronavirus immunity in the global population.

Brief communication: Chest radiography score in young COVID-19 patients: Does one size fit all?

During the SARS-CoV-2 pandemic, chest X-Ray (CXR) scores are essential to rapidly assess patients' prognoses. This study evaluates a published CXR score in a different national healthcare system. In our study, this CXR score maintains a prognostic role in predicting length of hospital stay, but not disease severity. However, our results show that the predictive role of CXR score could be influenced by socioeconomic status and healthcare system.

The clinical relevance of lymphocyte to monocyte ratio in patients with Idiopathic Pulmonary Fibrosis (IPF).

Disease course in Idiopathic Pulmonary Fibrosis (IPF) is highly heterogeneous and markers of disease progression would be helpful. Blood leukocyte count has been studied in cancer patients and a reduced lymphocyte to monocyte ratio (LMR) has been show to predict survival. Thus, we aimed to investigate the role of monocytes count and LMR in three distinct population of patients with IPF: 77 newly-diagnosed IPF, 40 with end-stage IPF and 17 IPF with lung cancer. In newly-diagnosed IPF patients, we observed a negative correlation between forced vital capacity (FVC) at diagnosis and both white blood cells and monocytes count (r = -0.24; p = 0.04 and r = -0.27; p = 0.01; respectively). Moreover, a high monocytes count was independently associated with functional decline (OR: 1.004, 95%CI 1.00-1.01; p = 0.03). In newly-diagnosed IPF, the LMR cut-off at diagnosis was 4.18 with an AUC of 0.67 (95%CI 0.5417-0.7960; p = 0.025), and overall survival was significantly worse in patients with a LMR<4.18 compared to patients with a LMR≥4.18 (HR: 6.88, 95%CI 2.55-18.5; p = 0.027). LMR was significantly lower in IPF patients with lung cancer compared to those newly diagnosed with IPF [2.2 (0.8-4.4), 3.5 (0.8-8.8); p < 0.0001] and those with end-stage disease [3.6 (2-6.5); p < 0.0001]. In conclusion, a LMR<4.18 is associated with significantly shorter survival in newly-diagnosed IPF patients. In addition, LMR is significantly lower in patients with IPF and lung cancer compared to patients with newly-diagnosed IPF. High monocytes count at baseline negatively correlates with FVC and is an independent predictor of disease progression in newly-diagnosed IPF patients.

Disease Severity and Prognosis of SARS-CoV-2 Infection in Hospitalized Patients Is Not Associated With Viral Load in Nasopharyngeal Swab.

Background: The impact of viral burden on severity and prognosis of patients hospitalized for Coronavirus Disease 2019 (COVID-19) is still a matter of debate due to controversial results. Herein, we sought to assess viral load in the nasopharyngeal swab and its association with severity score indexes and prognostic parameters. Methods: We included 127 symptomatic patients and 21 asymptomatic subjects with a diagnosis of SARS-CoV-2 infection obtained by reverse transcription polymerase chain reaction and presence of cycle threshold. According to the level of care needed during hospitalization, the population was categorized as high-intensity (HIMC, n = 76) or low intensity medical care setting (LIMC, n = 51). Results: Viral load did not differ among asymptomatic, LIMC, and HIMC SARS-CoV-2 positive patients [4.4 (2.9-5.3) vs. 4.8 (3.6-6.1) vs. 4.6 (3.9-5.7) log10 copies/ml, respectively; p = 0.31]. Similar results were observed when asymptomatic individuals were compared to hospitalized patients [4.4 (2.9-5.3) vs. 4.68 (3.8-5.9) log10 copies/ml; p = 0.13]. When the study population was divided in High (HVL, n = 64) and Low Viral Load (LVL, n = 63) group no differences were observed in disease severity at diagnosis. Furthermore, LVL and HVL groups did not differ with regard to duration of hospital stay, number of bacterial co-infections, need for high-intensity medical care and number of deaths. The viral load was not an independent risk factor for HIMC in an adjusted multivariate regression model (OR: 1.59; 95% CI: 0.46-5.55, p = 0.46). Conclusions: Viral load at diagnosis is similar in asymptomatic and hospitalized patients and is not associated with either worse outcomes during hospitalization. SARS CoV-2 viral load might not be the right tool to assist clinicians in risk-stratifying hospitalized patients.

SARS-CoV-2 antibody dynamics and transmission from community-wide serological testing in the Italian municipality of Vo'.

In February and March 2020, two mass swab testing campaigns were conducted in Vo', Italy. In May 2020, we tested 86% of the Vo' population with three immuno-assays detecting antibodies against the spike and nucleocapsid antigens, a neutralisation assay and Polymerase Chain Reaction (PCR). Subjects testing positive to PCR in February/March or a serological assay in May were tested again in November. Here we report on the results of the analysis of the May and November surveys. We estimate a seroprevalence of 3.5% (95% Credible Interval (CrI): 2.8-4.3%) in May. In November, 98.8% (95% Confidence Interval (CI): 93.7-100.0%) of sera which tested positive in May still reacted against at least one antigen; 18.6% (95% CI: 11.0-28.5%) showed an increase of antibody or neutralisation reactivity from May. Analysis of the serostatus of the members of 1,118 households indicates a 26.0% (95% CrI: 17.2-36.9%) Susceptible-Infectious Transmission Probability. Contact tracing had limited impact on epidemic suppression.

Prognostic role of MUC5B rs35705950 genotype in patients with idiopathic pulmonary fibrosis (IPF) on antifibrotic treatment.

BACKGROUND: A common variant located in the promoter region of MUC5B (rs35705950) is the strongest risk factor for sporadic and familiar IPF, as well as a predictor of outcome. However, there are no data on the effect of MUC5B rs35705950 genotype on the prognosis of IPF patients on antifibrotic treatment. The aim of this study is to determine, in a phenotypically well-characterized population of patients with IPF treated with antifibrotics, the impact of MUC5B rs35705950 genotype on disease progression and survival. METHODS: 88 IPF patients on antifibrotic treatment were followed-up from 2014 until transplantation, death or end of follow-up (December 2019). Disease progression was defined as a forced vital capacity (FVC) loss ≥ 5% per year. All patients were genotyped for MUC5B rs35705950 by PCR amplification and Sanger sequencing. RESULTS: Out of 88 patients, 61 (69%) carried the mutant T allele (TT or TG) and 27 (31%) did not (GG). Carriage of the MUC5B rs35705950 T allele was not associated with a faster decline in FVC. Conversely, at the end of the follow-up, overall survival in carriers of the TT/TG genotype was longer compared to that of the GG genotype carriers. FVC (L) at baseline and time to respiratory failure at rest were independent predictors of worse prognosis. CONCLUSIONS: In IPF patients on antifibrotic treatment, carriage of the MUC5B rs35705950 T allele is associated with longer survival, highlighting the usefulness of MUC5B genetic data in clinical decision making.

Characteristics and Prognostic Factors of Pulmonary Fibrosis After COVID-19 Pneumonia.

BACKGROUND: Few is known about the long-term pulmonary sequelae after COVID-19 infection. Hence, the aim of this study is to characterize patients with persisting pulmonary sequelae at follow-up after hospitalization. We also aimed to explore clinical and radiological predictors of pulmonary fibrosis following COVID-19. METHODS: Two hundred and 20 consecutive patients were evaluated at 3-6 months after discharge with high-resolution computed tomography (HRCT) and categorized as recovered (REC) or not recovered (NOT-REC). Both HRCTs at hospitalization (HRCT0), when available, and HRCT1 during follow-up were analyzed semiquantitatively as follows: ground-glass opacities (alveolar score, AS), consolidations (CONS), and reticulations (interstitial score, IS). RESULTS: A total of 175/220 (80%) patients showed disease resolution at their initial radiological evaluation following discharge. NOT-REC patients (45/220; 20%) were mostly older men [66 (35-85) years vs. 56 (19-87); p = 0.03] with a longer in-hospital stay [16 (0-75) vs. 8 (1-52) days; p < 0.0001], and lower P/F at admission [233 (40-424) vs. 318 (33-543); p = 0.04]. Moreover, NOT-REC patients presented, at hospital admission, higher ALV [14 (0.0-62.0) vs. 4.4 (0.0-44.0); p = 0.0005], CONS [1.9 (0.0-26.0) vs. 0.4 (0.0-18.0); p = 0.0064], and IS [11.5 (0.0- 29.0) vs. 0.0 (0.0-22.0); p < 0.0001] compared to REC patients. On multivariate analysis, the presence of CONS and IS at HRCT0 was independent predictors of radiological sequelae at follow-up [OR 14.87 (95% CI: 1.25-175.8; p = 0.03) and 28.9 (95% CI: 2.17-386.6; p = 0.01, respectively)]. CONCLUSIONS: In our population, only twenty percent of patients showed persistent lung abnormalities at 6 months after hospitalization for COVID-19 pneumonia. These patients are predominantly older men with longer hospital stay. The presence of reticulations and consolidation on HRCT at hospital admission predicts the persistence of radiological abnormalities during follow-up.

Clinical Features and Chest Imaging as Predictors of Intensity of Care in Patients with COVID-19.

Coronavirus disease 2019 (COVID-19) has rapidly become a global pandemic with lung disease representing the main cause of morbidity and mortality. Conventional chest-X ray (CXR) and ultrasound (US) are valuable instruments to assess the extent of lung involvement. We investigated the relationship between CXR scores on admission and the level of medical care required in patients with COVID-19. Further, we assessed the CXR-US correlation to explore the role of ultrasound in monitoring the course of COVID-19 pneumonia. Clinical features and CXR scores were obtained at admission and correlated with the level of intensity of care required [high- (HIMC) versus low-intensity medical care (LIMC)]. In a subgroup of patients, US findings were correlated with clinical and radiographic parameters. On hospital admission, CXR global score was higher in HIMCs compared to LIMC. Smoking history, pO2 on admission, cardiovascular and oncologic diseases were independent predictors of HIMC. The US score was positively correlated with FiO2 while the correlation with CXR global score only trended towards significance. Our study identifies clinical and radiographic features that strongly correlate with higher levels of medical care. The role of lung ultrasound in this setting remains undetermined and needs to be explored in larger prospective studies.

CA 19-9 serum levels in patients with end-stage idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases (ILDs): Correlation with functional decline.

Idiopathic pulmonary fibrosis presents a progressive and heterogeneous functional decline. CA 19-9 has been proposed as biomarker to predict disease course, but its role remains unclear. We assessed CA 19-9 levels and clinical data in end-stage ILD patients (48 IPF and 20 non-IPF ILD) evaluated for lung transplant, to correlate these levels with functional decline. Patients were categorized based on their rate of functional decline as slow (n = 20; ΔFVC%pred ≤ 10%/year) or rapid progressors (n = 28; ΔFVC%pred ≥ 10%/year). Nearly half of the entire patients (n = 32; 47%) had CA 19-9 levels ≥37kU/L. CA 19-9 levels in IPF were not different from non-IPF ILD populations, however, the latter group had a median CA 19-9 level above the normal cut-off value of 37 KU/l (60 [17-247] kU/L). Among IPF patients, CA 19-9 was higher in slow than in rapid progressors with a trend toward significance (33vs17kU/L; p = 0.055). In the whole population, CA19-9 levels were inversely related with ΔFVC/year (r = -0.261; p = 0.03), this correlation remained in IPF patients, particularly in rapid progressors (r = -0.51; p = 0.005), but not in non. Moreover, IPF rapid progressors with normal CA 19-9 levels showed the greater ΔFVC/year compared to those with abnormal CA 19-9 (0.95 vs. 0.65 L/year; p = 0.03). In patients with end-stage ILD, CA 19-9 may represent a marker of disease severity, whereas its level is inversely correlated with functional decline, particularly among IPF rapid progressors.

Suppression of a SARS-CoV-2 outbreak in the Italian municipality of Vo'.

On 21 February 2020, a resident of the municipality of Vo', a small town near Padua (Italy), died of pneumonia due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection1. This was the first coronavirus disease 19 (COVID-19)-related death detected in Italy since the detection of SARS-CoV-2 in the Chinese city of Wuhan, Hubei province2. In response, the regional authorities imposed the lockdown of the whole municipality for 14 days3. Here we collected information on the demography, clinical presentation, hospitalization, contact network and the presence of SARS-CoV-2 infection in nasopharyngeal swabs for 85.9% and 71.5% of the population of Vo' at two consecutive time points. From the first survey, which was conducted around the time the town lockdown started, we found a prevalence of infection of 2.6% (95% confidence interval (CI): 2.1-3.3%). From the second survey, which was conducted at the end of the lockdown, we found a prevalence of 1.2% (95% CI: 0.8-1.8%). Notably, 42.5% (95% CI: 31.5-54.6%) of the confirmed SARS-CoV-2 infections detected across the two surveys were asymptomatic (that is, did not have symptoms at the time of swab testing and did not develop symptoms afterwards). The mean serial interval was 7.2 days (95% CI: 5.9-9.6). We found no statistically significant difference in the viral load of symptomatic versus asymptomatic infections (P = 0.62 and 0.74 for E and RdRp genes, respectively, exact Wilcoxon-Mann-Whitney test). This study sheds light on the frequency of asymptomatic SARS-CoV-2 infection, their infectivity (as measured by the viral load) and provides insights into its transmission dynamics and the efficacy of the implemented control measures.