Objective Magnetoreception, the remarkable ability of diverse animals to sense and utilize the geomagnetic field for orientation and navigation, remains a molecularly unresolved mystery in sensory biology. The putative magnetoreceptor (MagR, previously known as IscA1) is a highly conserved iron-sulfur protein implicated in both magnetoreception and iron metabolism; however, the functional diversity among its cross-species homologs remains poorly understood. Cellular morphology is a key genetically determined trait that can be altered through genetic or environmental modifications—a process known as cell morphology engineering. Constructing engineered cells with specific morphological features and magnetic sensitivity to achieve remote, non-invasive magnetic modulation represents a crucial goal in this field with significant application potential. Therefore, this study aims to systematically investigate the effects of MagR heterologous expression on bacterial morphology and magnetic sensing capabilities, screen for MagR-based magnetically sensitive morphology engineering pathways, and reveal the underlying molecular mechanisms. Methods We systematically screened 28 MagR homologous genes from diverse prokaryotic and animal taxa to evaluate their expression and corresponding phenotypic effects in Escherichia coli (E. coli). To compare the differential magnetic responses among bacteria expressing various recombinant MagR proteins, we utilized high-throughput automated bright-field microscopic imaging and scanning electron microscopy (SEM). Furthermore, comprehensive biochemical and biophysical characterizations of iron and iron-sulfur cluster binding were performed using Ferrozine colorimetric assays, electron paramagnetic resonance (EPR) spectroscopy, ultraviolet-visible (UV-Vis) absorption, and circular dichroism (CD) spectroscopy. Additionally, 100 mT static magnetic field (SMF) exposure experiments were conducted to assess magnetically tunable phenotypes, while the intrinsic magnetic properties of purified MagR proteins were directly measured using a superconducting quantum interference device (SQUID) magnetometer. Results Our results demonstrated that the heterologous expression of MagR homologs induced varying degrees of bacterial filamentation. From this comprehensive screen, two distinct morphological patterns were identified: hydra (Hydra vulgaris) MagR (hyMagR) promoted uniform cell elongation and filamentation, exhibiting robust magnetic sensitivity manifested as significantly enhanced filamentation under the 100 mT SMF. In contrast, pigeon (Columba livia) MagR (clMagR) induced only low-frequency, extreme filamentation (sporadically exceeding 80 μm) with a relatively weaker magnetic morphological response. Mechanistically, our data unambiguously proved that these phenotypic differences are primarily driven by distinct iron redox preferences rather than total cellular iron accumulation. Specifically, hyMagR preferentially binds ferrous iron (Fe²⁺), whereas clMagR favors ferric iron (Fe³⁺) and forms more stable iron-sulfur clusters. Intriguingly, although SQUID magnetometry showed that purified clMagR exhibited approximately five-fold higher mass magnetic susceptibility than hyMagR, its cellular magnetic response was weaker. We hypothesize that the Fe²⁺-preferred intracellular environment associated with hyMagR overexpression primes the cell for enhanced generation of reactive oxygen species (ROS) via the Fenton reaction. Exposure to an SMF synergizes with this primed redox state, triggering the bacterial SOS response and upregulating cell division inhibitors to efficiently induce uniform filamentation. Conclusion Our findings identify the Fe²⁺/Fe³⁺ redox state as a critical determinant of MagR-mediated morphological remodeling and magnetic responsiveness. This discovery suggests a potential strategy for engineering magnetically responsive cellular systems for synthetic biology applications, and provides a plausible framework, which potentially combines intrinsic protein magnetism with redox-state modulation, for further investigating the evolutionary mechanisms of MagR-mediated magnetoreception.

Objective Magnetoreception, the remarkable ability of diverse animals to sense and utilize the geomagnetic field for orientation and navigation, remains a molecularly unresolved mystery in sensory biology. The putative magnetoreceptor (MagR, previously known as IscA1) is a highly conserved iron-sulfur protein implicated in both magnetoreception and iron metabolism; however, the functional diversity among its cross-species homologs remains poorly understood. Cellular morphology is a key genetically determined trait that can be altered through genetic or environmental modifications—a process known as cell morphology engineering. Constructing engineered cells with specific morphological features and magnetic sensitivity to achieve remote, non-invasive magnetic modulation represents a crucial goal in this field with significant application potential. Therefore, this study aims to systematically investigate the effects of MagR heterologous expression on bacterial morphology and magnetic sensing capabilities, screen for MagR-based magnetically sensitive morphology engineering pathways, and reveal the underlying molecular mechanisms. Methods We systematically screened 28 MagR homologous genes from diverse prokaryotic and animal taxa to evaluate their expression and corresponding phenotypic effects in Escherichia coli (E. coli). To compare the differential magnetic responses among bacteria expressing various recombinant MagR proteins, we utilized high-throughput automated bright-field microscopic imaging and scanning electron microscopy (SEM). Furthermore, comprehensive biochemical and biophysical characterizations of iron and iron-sulfur cluster binding were performed using Ferrozine colorimetric assays, electron paramagnetic resonance (EPR) spectroscopy, ultraviolet-visible (UV-Vis) absorption, and circular dichroism (CD) spectroscopy. Additionally, 100 mT static magnetic field (SMF) exposure experiments were conducted to assess magnetically tunable phenotypes, while the intrinsic magnetic properties of purified MagR proteins were directly measured using a superconducting quantum interference device (SQUID) magnetometer. Results Our results demonstrated that the heterologous expression of MagR homologs induced varying degrees of bacterial filamentation. From this comprehensive screen, two distinct morphological patterns were identified: hydra (Hydra vulgaris) MagR (hyMagR) promoted uniform cell elongation and filamentation, exhibiting robust magnetic sensitivity manifested as significantly enhanced filamentation under the 100 mT SMF. In contrast, pigeon (Columba livia) MagR (clMagR) induced only low-frequency, extreme filamentation (sporadically exceeding 80 μm) with a relatively weaker magnetic morphological response. Mechanistically, our data unambiguously proved that these phenotypic differences are primarily driven by distinct iron redox preferences rather than total cellular iron accumulation. Specifically, hyMagR preferentially binds ferrous iron (Fe²⁺), whereas clMagR favors ferric iron (Fe³⁺) and forms more stable iron-sulfur clusters. Intriguingly, although SQUID magnetometry showed that purified clMagR exhibited approximately five-fold higher mass magnetic susceptibility than hyMagR, its cellular magnetic response was weaker. We hypothesize that the Fe²⁺-preferred intracellular environment associated with hyMagR overexpression primes the cell for enhanced generation of reactive oxygen species (ROS) via the Fenton reaction. Exposure to an SMF synergizes with this primed redox state, triggering the bacterial SOS response and upregulating cell division inhibitors to efficiently induce uniform filamentation. Conclusion Our findings identify the Fe²⁺/Fe³⁺ redox state as a critical determinant of MagR-mediated morphological remodeling and magnetic responsiveness. This discovery suggests a potential strategy for engineering magnetically responsive cellular systems for synthetic biology applications, and provides a plausible framework, which potentially combines intrinsic protein magnetism with redox-state modulation, for further investigating the evolutionary mechanisms of MagR-mediated magnetoreception.

AIM To investigate the effects of rice wine type and wine processing method on chemical constituents and anti-coagulation effect of Angelicae sinensis Radix.METHODS Wine-washed products and wine-stir-fried products were prepared by different types and ages of rice wine,respectively,after which HPLC was adopted in the content determination of tryptophan,chlorogenic acid,vanillic acid,phthalic acid,ferulic acid,senkyunolide I,senkyunolide H,coniferyl ferulate and ligustilide,and PT,APTT,TT were detected in rabbit plasma.RESULTS Phenolic acids and volatile constituents demonstrated lower contents in the wine-stir-fried products than those in the raw product(P＜0.05),while those in the wine-washed products displayed no obvious changes(except for senkyunolide I)(P＞0.05).The contents of volatile constituents in the wine-washed products were higher than those in the wine-stir-fried products(P＜0.05).After being processed with dry rice wine,various constituents exhibited increased contents as compared with those after being processed with sweet rice wine(P＜0.05).Compared with the raw product,prolonged PT,APTT and TT were observable in the processed products prepared by 3-year semi-dry rice wine(P＜0.05).CONCLUSION The optimal rice wine type is determined to be 3-year semi-dry.Wine-washed Angelicae sinensis Radix shows high contents of ferulic acid and volatile constituents,whose activating blood and resolving stasis effect may be stronger.

AIM To investigate the effects of rice wine type and wine processing method on chemical constituents and anti-coagulation effect of Angelicae sinensis Radix.METHODS Wine-washed products and wine-stir-fried products were prepared by different types and ages of rice wine,respectively,after which HPLC was adopted in the content determination of tryptophan,chlorogenic acid,vanillic acid,phthalic acid,ferulic acid,senkyunolide I,senkyunolide H,coniferyl ferulate and ligustilide,and PT,APTT,TT were detected in rabbit plasma.RESULTS Phenolic acids and volatile constituents demonstrated lower contents in the wine-stir-fried products than those in the raw product(P＜0.05),while those in the wine-washed products displayed no obvious changes(except for senkyunolide I)(P＞0.05).The contents of volatile constituents in the wine-washed products were higher than those in the wine-stir-fried products(P＜0.05).After being processed with dry rice wine,various constituents exhibited increased contents as compared with those after being processed with sweet rice wine(P＜0.05).Compared with the raw product,prolonged PT,APTT and TT were observable in the processed products prepared by 3-year semi-dry rice wine(P＜0.05).CONCLUSION The optimal rice wine type is determined to be 3-year semi-dry.Wine-washed Angelicae sinensis Radix shows high contents of ferulic acid and volatile constituents,whose activating blood and resolving stasis effect may be stronger.

Objective To investigate the improvement effect and mechanism of marmesin on cognitive impairment in Alzheimer's disease(AD)mice.Methods Fifty mice were randomly divided into five groups:blank group,model group,low-and high-dose marmesin groups and donepezil(positive drug)group,with 10 mice in each group.After 21 days of continuous administration,except for the blank group,the mice in other groups were given intraperitoneal injection of scopolamine to establish the AD model.Network pharmacology was used to construct the protein-protein interaction(PPI)network of common targets of marmesin in the treatment of AD,and gene ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment analysis were performed to provide further research direction.The cognitive function of AD model mice was evaluated by Morris water maze,open field test and new object recognition test.Nissl staining was used to observe the damage of hippocampal neurons.The levels of acetylcholine(Ach),acetylcholine transferase(ChAT),acetylcholinesterase(AChE),reactive oxygen species(ROS),malondialdehyde(MDA)and catalase(CAT)in hippocampus of mice were detected by kit.The protein expression levels of interleukin 6(IL-6),interleukin 1β(IL-1 β),tumor necrosis factor α(TNF-α),nuclear factor E2-related factor 2(NRF2),silent information regulator homologous protein 3(SIRT3),Kelch-like ECH-associated protein 1(KEAP1),quinone oxidoreductase 1(NQO1)and heme oxygenase 1(HO-1)in hippocampus were detected by Western Blot.Results Compared with the model group,the latency of Morris water maze test was significantly shortened in the high-dose marmesin group,the time of entering the target area in the open field new object test and the movement distance in the central area of the open field were prolonged,the number of neurons in the hippocampal CA1 and CA3 regions was significantly increased,the levels of ChAT and Ach in the hippocampus were significantly increased,AChE level was significantly decreased,CAT level was significantly increased,ROS and MDA levels were significantly decreased,TNF-α expression level was decreased,SIRT3 and HO-1 expression levels were increased,and KE AP1 protein expression level was decreased,the differences being statistically significant(P＜0.05 or P＜0.01 or P＜0.001).Conclusion Marmesin can effectively improve the learning and memory impairment of AD mice,and its mechanism may be related to the activation of NRF2/SIRT3 signaling pathway,thereby alleviating oxidative stress level and neuroinflammation,and repairing cholinergic neuron function.

Objective To investigate the incidence rate,clinical characteristics,and prognosis of neonatal stroke in Shenzhen,China.Methods Led by Shenzhen Children's Hospital,the Shenzhen Neonatal Data Collaboration Network organized 21 institutions to collect 36 cases of neonatal stroke from January 2020 to December 2022.The incidence,clinical characteristics,treatment,and prognosis of neonatal stroke in Shenzhen were analyzed.Results The incidence rate of neonatal stroke in 21 hospitals from 2020 to 2022 was 1/15 137,1/6 060,and 1/7 704,respectively.Ischemic stroke accounted for 75％(27/36);boys accounted for 64％(23/36).Among the 36 neonates,31(86％)had disease onset within 3 days after birth,and 19(53％)had convulsion as the initial presentation.Cerebral MRI showed that 22 neonates(61％)had left cerebral infarction and 13(36％)had basal ganglia infarction.Magnetic resonance angiography was performed for 12 neonates,among whom 9(75％)had involvement of the middle cerebral artery.Electroencephalography was performed for 29 neonates,with sharp waves in 21 neonates(72％)and seizures in 10 neonates(34％).Symptomatic/supportive treatment varied across different hospitals.Neonatal Behavioral Neurological Assessment was performed for 12 neonates(33％,12/36),with a mean score of(32±4)points.The prognosis of 27 neonates was followed up to around 12 months of age,with 44％(12/27)of the neonates having a good prognosis.Conclusions Ischemic stroke is the main type of neonatal stroke,often with convulsions as the initial presentation,involvement of the middle cerebral artery,sharp waves on electroencephalography,and a relatively low neurodevelopment score.Symptomatic/supportive treatment is the main treatment method,and some neonates tend to have a poor prognosis.

Objective: Total neoadjuvant therapy has been used to improve tumor responses and prevent distant metastases in patients with locally advanced rectal cancer (LARC). Patients with complete clinical responses (cCR) then have the option of choosing a watch and wait (W&W) strategy and organ preservation. It has recently been shown that hypofractionated radiotherapy has better synergistic effects with PD-1/PD-L1 inhibitors than does conventionally fractionated radiotherapy, increasing the sensitivity of microsatellite stable (MSS) colorectal cancer to immunotherapy. Thus, in this trial we aimed to determine whether total neoadjuvant therapy comprising short-course radiotherapy (SCRT) combined with a PD-1 inhibitor improves the degree of tumor regression in patients with LARC. Methods: TORCH is a prospective, multicenter, randomized, phase II trial (TORCH Registration No. NCT04518280). Patients with LARC (T3-4/N+M0, distance from anus ≤10 cm) are eligible and are randomly assigned to consolidation or induction arms. Those in the consolidation arm receive SCRT (25Gy/5 Fx), followed by six cycles of toripalimab plus capecitabine and oxaliplatin (ToriCAPOX). Those in the induction arm receive two cycles of ToriCAPOX, then undergo SCRT, followed by four cycles of ToriCAPOX. Patients in both groups undergo total mesorectal excision (TME) or can choose a W&W strategy if cCR has been achieved. The primary endpoint is the complete response rate (CR, pathological complete response [pCR] plus continuous cCR for more than 1 year). The secondary endpoints include rates of Grade 3-4 acute adverse effects (AEs) etc. Results: Up to 30 September 2022, 62 patients attending our center were enrolled (Consolidation arm: 34, Induction arm:28). Their median age was 53 (27-69) years. Fifty-nine of them had MSS/pMMR type cancer (95.2%), and only three MSI-H/dMMR. Additionally, 55 patients (88.7%) had Stage III disease. The following important characteristics were distributed as follows: lower location (≤5 cm from anus, 48/62, 77.4%), deeper invasion by primary lesion (cT4 7/62, 11.3%; mesorectal fascia involved 17/62, 27.4%), and high risk of distant metastasis (cN2 26/62, 41.9%; EMVI+ 11/62, 17.7%). All 62 patients completed the SCRT and at least five cycles of ToriCAPOX, 52/62 (83.9%) completing six cycles of ToriCAPOX. Finally, 29 patients achieved cCR (46.8%, 29/62), 18 of whom decided to adopt a W&W strategy. TME was performed on 32 patients. Pathological examination showed 18 had achieved pCR, four TRG 1, and 10 TRG 2-3. The three patients with MSI-H disease all achieved cCR. One of these patients was found to have pCR after surgery whereas the other two adopted a W&W strategy. Thus, the pCR and CR rates were 56.2% (18/32) and 58.1% (36/62), respectively. The TRG 0-1 rate was 68.8% (22/32). The most common non-hematologic AEs were poor appetite (49/60, 81.7%), numbness (49/60, 81.7%), nausea (47/60, 78.3%) and asthenia (43/60, 71.7%); two patients did not complete this survey. The most common hematologic AEs were thrombocytopenia (48/62, 77.4%), anemia (47/62, 75.8%), leukopenia/neutropenia (44/62, 71.0%) and high transaminase (39/62, 62.9%). The main Grade III-IV AE was thrombocytopenia (22/62, 35.5%), with three patients (3/62, 4.8%) having Grade IV thrombocytopenia. No Grade V AEs were noted. Conclusions: SCRT-based total neoadjuvant therapy combined with toripalimab can achieve a surprisingly good CR rate in patients with LARC and thus has the potential to offer new treatment options for organ preservation in patients with MSS and lower-location rectal cancer. Meanwhile, the preliminary findings of a single center show good tolerability, the main Grade III-IV AE being thrombocytopenia. The significant efficacy and long-term prognostic benefit need to be determined by further follow-up.
Humans ; Middle Aged ; Antineoplastic Combined Chemotherapy Protocols/therapeutic use* ; Chemoradiotherapy ; Immune Checkpoint Inhibitors/therapeutic use* ; Neoadjuvant Therapy ; Prospective Studies ; Rectal Neoplasms/pathology* ; Thrombocytopenia/drug therapy* ; Treatment Outcome ; Adult ; Aged

OBJECTIVE: To analyze the association between outdoor artificial light-at-night (ALAN) exposure and overweight and obesity among children and adolescents aged 9 to 18 years in China. METHODS: Using follow-up data of 5 540 children and adolescents aged 9 to 18 years conducted from November 2019 to November 2020 in eight provinces of China, latitude and longitude were determined based on school addresses, and the mean monthly average nighttime irradiance at the location of 116 schools was extracted by the nearest neighbor method to obtain the mean outdoor ALAN exposure [unit: nW/(cm²·sr)] for each school. Four indicators of overweight and obesity outcomes were included: Baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence. Mixed effects Logistic regression was used to explore the association between ALAN exposure levels (divided into quintiles Q1-Q5) and baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence. In addition, a natural cubic spline function was used to explore the exposure response association between ALAN exposure (a continuous variable) and the outcomes. RESULTS: The prevalence of baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence among the children and adolescents in this study were 21.6%, 16.3%, 2.9% and 12.8%, respectively. The OR value for the association between ALAN exposure and baseline overweight and obesity was statistically significant when ALAN exposure levels reached Q4 or Q5, 1.90 (95%CI: 1.26-2.86) and 1.77 (95%CI: 1.11-2.83), respectively, compared with the children and adolescents in the Q1 group of ALAN exposure. Similar to the results for baseline overweight and obesity, the OR values for the association with persistent overweight and obesity were 1.89 (95%CI: 1.20-2.99) and 1.82 (95%CI: 1.08-3.06) when ALAN exposure levels reached Q4 or Q5, respectively, but none of the OR values for the association between ALAN and overweight and obesity progression and overweight and obesity incidence were statistically significant. Fitting a natural cubic spline function showed a non-linear trend between ALAN exposure and persistent overweight and obesity. CONCLUSION There is a positive association between ALAN exposure and overweight and obesity in children and adolescents, and the promotion of overweight obesity in children and adolescents by ALAN tends to have a cumulative effect rather than an immediate effect. In the future, while focusing on the common risk factors for overweight and obesity in children and adolescents, there is a need to improve the overweight and obesity-causing nighttime light exposure environment.
Humans ; Adolescent ; Child ; Overweight/etiology* ; Pediatric Obesity/etiology* ; Light Pollution ; Risk Factors ; China/epidemiology*

OBJECTIVE: To observe the effects of electroacupuncture (EA) pretreatment on cardiac function, sympathetic nerve activity, indexes of myocardial injury and GABA_A receptor in fastigial nucleus in rats with myocardial ischemia reperfusion injury (MIRI), and to explore the neuroregulatory mechanism of EA pretreatment in improving MIRI. METHODS: A total of 60 male SD rats were randomly divided into a sham operation group, a model group, an EA group, an agonist group and an agonist+EA group, 12 rats in each group. The MIRI model was established by ligation of the left anterior descending coronary artery. EA was applied at bilateral "Shenmen" (HT 7) and "Tongli" (HT 5) in the EA group and the agonist+EA group, with continuous wave, in frequency of 2 Hz and intensity of 1 mA, 30 min each time, once a day for 7 consecutive days. After intervention, the MIRI model was established. In the agonist group, the muscone (agonist of GABA_A receptor, 1 g/L) was injected in fastigial nucleus for 7 consecutive days before modeling, 150 μL each time, once a day. In the agonist+EA group, the muscone was injected in fastigial nucleus 30 min before EA intervention. The data of electrocardiogram was collected by PowerLab standard Ⅱ lead, and ST segment displacement and heart rate variability (HRV) were analyzed; the serum levels of norepinephrine (NE), creatine kinase isoenzyme MB (CK-MB) and cardiac troponin I (cTnI) were detected by ELISA; the myocardial infarction area was measured by TTC staining; the morphology of myocardial tissue was observed by HE staining; the positive expression and mRNA expression of GABA_A receptor in fastigial nucleus were detected by immunohistochemistry and real-time PCR. RESULTS: Compared with the sham operation group, in the model group, ST segment displacement and ratio of low frequency to high frequency (LF/HF) of HRV were increased (P<0.01), HRV frequency domain analysis showed enhanced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were increased (P<0.01), the percentage of myocardial infarction area was increased (P<0.01), myocardial fiber was broken and interstitial edema was serious, the positive expression and mRNA expression of GABA_A receptor in fastigial nucleus were increased (P<0.01). Compared with the model group, in the EA group, ST segment displacement and LF/HF ratio were decreased (P<0.01), HRV frequency domain analysis showed reduced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were decreased (P<0.01), the percentage of myocardial infarction area was decreased (P<0.01), myocardial fiber breakage and interstitial edema were lightened, the positive expression and mRNA expression of GABA_A receptor in fastigial nucleus were decreased (P<0.01). Compared with the EA group, in the agonist group and the agonist+EA group, ST segment displacement and LF/HF ratio were increased (P<0.01), HRV frequency domain analysis showed enhanced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were increased (P<0.01), the percentage of myocardial infarction area was increased (P<0.01), myocardial fiber breakage and interstitial edema were aggravated, the positive expression and mRNA expression of GABA_A receptor in fastigial nucleus were increased (P<0.01). CONCLUSION EA pretreatment can improve the myocardial injury in MIRI rats, and its mechanism may be related to the inhibition of GABA_A receptor expression in fastigial nucleus, thereby down-regulating the excitability of sympathetic nerve.
Male ; Animals ; Rats ; Rats, Sprague-Dawley ; Cerebellar Nuclei ; Electroacupuncture ; Myocardial Reperfusion Injury/therapy* ; Receptors, GABA-A/genetics* ; RNA, Messenger

This study collected epidemic data of COVID-19 in Zhengzhou from January 1 to January 20 in 2022. The epidemiological characteristics of the local epidemic in Zhengzhou High-tech Zone caused by the SARS-CoV-2 Delta variant were analyzed through epidemiological survey and big data analysis, which could provide a scientific basis for the prevention and control of the Delta variant. In detail, a total of 276 close contacts and 599 secondary close contacts were found in this study. The attack rate of close contacts and secondary close contacts was 5.43% (15/276) and 0.17% (1/599), respectively. There were 10 confirmed cases associated with the chain of transmission. Among them, the attack rates in close contacts of the first, second, third, fourth and fifth generation cases were 20.00% (5/25), 17.86% (5/28), 0.72% (1/139) and 14.81% (4/27), 0 (0/57), respectively. The attack rates in close contacts after sharing rooms/beds, having meals, having neighbor contacts, sharing vehicles with the patients, having same space contacts, and having work contacts were 26.67%, 9.10%, 8.33%, 4.55%, 1.43%, and 0 respectively. Collectively, the local epidemic situation in Zhengzhou High-tech Zone has an obvious family cluster. Prevention and control work should focus on decreasing family clusters of cases and community transmission.
Humans ; SARS-CoV-2 ; COVID-19 ; Epidemics ; Incidence