Environmental Factors and Kawasaki Disease Onset in Emilia-Romagna, Italy

Incidence and seasonality of Kawasaki disease in children in the Philippines, and its association with ambient air temperature

Background

Despite an unknown cause, Kawasaki disease (KD) is currently the primary leading cause of acquired heart disease in developed countries in children and has been increasing in recent years. Research efforts have explored environmental factors related to KD, but they are still unclear especially in the tropics. We aimed to describe the incidence of KD in children, assess its seasonality, and determine its association with ambient air temperature in the National Capital Region (NCR), Philippines from January 2009 to December 2019.

Methods

Monthly number of KD cases from the Philippine Pediatric Society (PPS) disease registry was collected to determine the incidence of KD. A generalized linear model (GLM) with quasi-Poisson regression was utilized to assess the seasonality of KD and determine its association with ambient air temperature after adjusting for the relevant confounders.

Results

The majority of KD cases (68.52%) occurred in children less than five years old, with incidence rates ranging from 14.98 to 23.20 cases per 100,000 population, and a male-to-female ratio of 1.43:1. Seasonal variation followed a unimodal shape with a rate ratio of 1.13 from the average, peaking in March and reaching the lowest in September. After adjusting for seasonality and long-term trend, every one-degree Celsius increase in the monthly mean temperature significantly increased the risk of developing KD by 8.28% (95% CI: 2.12%, 14.80%). Season-specific analysis revealed a positive association during the dry season (RR: 1.06, 95% CI: 1.01, 1.11), whereas no evidence of association was found during the wet season (RR: 1.10, 95% CI: 0.95, 1.27).

Conclusion

We have presented the incidence of KD in the Philippines which is relatively varied from its neighboring countries. The unimodal seasonality of KD and its linear association with temperature, independent of season and secular trend, especially during dry season, may provide insights into its etiology and may support enhanced KD detection efforts in the country.

The etiologies of Kawasaki disease

Kawasaki disease (KD) is a systemic vasculitis that affects young children and can result in coronary artery aneurysms. The etiology is currently unknown, but new clues from the epidemiology of KD in Japan, the country of highest incidence, are beginning to shed light on what may trigger this acute inflammatory condition. Additional clues from the global changes in KD incidence during the COVID-19 pandemic, coupled with a new birth cohort study from Japan, point to the potential role of person-to-person transmission of an infectious agent. However, the rising incidence of KD in Japan, with coherent waves across the entire country, points to an increasing intensity of exposure that cannot be explained by person-to-person spread. This Review discusses new and historical observations that guide us toward a better understanding of KD etiology and explores hypotheses and interpretations that can provide direction for future investigations. Once the etiology of KD is determined, accurate diagnostic tests will become available, and new, less expensive, and more effective targeted therapies will likely be possible. Clearly, solving the mystery of the etiologies of KD remains a priority for pediatric research.

Short-term exposure to ozone may trigger the onset of Kawasaki disease: An individual-level, case-crossover study in East China

Kawasaki disease (KD) is an acute, systemic vasculitis that primarily affects children aged under the age of 5. While environmental factors have been linked to the development of KD, the specific role of ozone (O3) pollution in triggering the disease onset remains uncertain. This study aimed to examine the associations between short-term O3 exposure and KD onset in children. Utilizing a satellite-based model with a spatial resolution of 1 × 1 km, we matched 1808 KD patients (out of a total of 6115 eligible individuals) to pre-onset ozone exposures based on their home addresses in East China between 2013 and 2020. Our findings revealed a significant association of O3 exposure with KD onset on the day of onset (lag 0 day). However, this association attenuated and became statistically insignificant on lag 1 and lag 2 days. Each interquartile range (52.32 μg/m3) increase in O3 concentration at lag 0 day was associated with a 16.2% (95% CI: 3.6%, 30.3%) increased risk of KD onset. The E-R curve for O3 exhibited a plateau at low concentrations and then increased rapidly at concentrations ≥75 μg/m3. Notably, these associations were stronger in male children, younger children (<2 years of age) and patients experiencing KD onset during the warm season. This study provides novel epidemiological evidence indicating that short-term O3 exposure is associated with an increased risk of childhood KD onset. These findings emphasized the importance of considering this environmental risk factor in KD prevention strategies.

Emerging evidence of microbial infection in causing systematic immune vasculitis in Kawasaki disease

Kawasaki disease (KD) is a systematic vasculitis that is often complicated by coronary artery lesions and is a leading cause of acquired heart disease in developed countries. Previous studies have suggested that genetic susceptibility, together with an inducing infectious agent, could be involved in KD pathogenesis; however, the precise causative agent of this disease remains unknown. Moreover, there are still debates concerning whether KD is an infectious disease or an autoimmune disease, although many studies have begun to show that various pathogens functioning as critical inducers could activate different kinds of immune cells, consequently leading to the dysfunction of endothelial cells and systematic vasculitis. Here in this review, we attempt to summarize all the available evidence concerning pathogen infections associated with KD pathogenesis. We also discuss the related mechanisms, present a future perspective, and identify the open questions that remain to be investigated, thereby providing a comprehensive description of pathogen infections and their correlations with the host immune system in leading to KD.

Integration of scRNA-Seq and bulk RNA-Seq uncover perturbed immune cell types and pathways of Kawasaki disease

Introduction

Kawasaki disease (KD) is an acute febrile illness primarily affecting children and characterized by systemic inflammation and vasculitis that can lead to coronary artery complications. The aim of this study was to gain a comprehensive understanding of immune dysregulation in KD.

Methods

To this end, we employed integration of single-cell RNA sequencing (scRNA-Seq) and bulk RNA sequencing (bulk RNA-Seq) data. Furthermore, we conducted flow cytometry analysis for a cohort of 82 KD patients.

Results

Our analysis revealed significant heterogeneity within immune cell populations in KD patients, with distinct clusters of T cells, B cells, and natural killer (NK) cells. Importantly, CD4+ naïve T cells in KD patients were found to predominantly differentiate into Treg cells and Th2 cells, potentially playing a role in the excessive inflammation and vascular damage characteristic of the disease. Dysregulated signaling pathways were also identified, including the mTOR signaling pathway, cardiomyopathy pathway, COVID-19 signaling pathway, and pathways involved in bacterial or viral infection.

Discussion

These findings provide insights into the immunopathogenesis of KD, emphasizing the importance of immune cell dysregulation and dysregulated signaling pathways. Integration of scRNA-Seq and bulk RNA-Seq data offers a comprehensive view of the molecular and cellular alterations in KD and highlights potential therapeutic targets for further investigation. Validation and functional studies are warranted to elucidate the roles of the identified immune cell types and pathways in KD pathogenesis and to develop targeted interventions to improve patient outcomes.

Prenatal and early life exposure to air pollution and the incidence of Kawasaki disease

Kawasaki disease (KD) is the most common form of acquired pediatric cardiac disease in the developed world. However, its etiology is still unclear. Epidemiological studies have shown that air pollution is a plausible risk factor in stimulating oxidative stress, inducing inflammation and causing autoimmune diseases. This study aims to assess the connections between prenatal and early life air pollution exposure to the incidence of KD. The main data source of this nationwide longitudinal study was the National Health Insurance Research Database (NHIRD) of Taiwan. NHIRD was linked with Taiwan Maternal and Child Health Database to establish the link between mothers and children. In total, 4192 KD cases involving children under 6 years of age were identified between January 2004 and December 2010. Children in the control group were randomly selected at a 1:4 ratio and matched using their age and index year. Integrated data for the air pollutants were obtained from 71 Environmental Protection Agency monitoring stations across Taiwan. Patients who had main admission diagnosis of KD and subsequently received intravenous immunoglobulin treatment were defined as incidence cases. Ambient exposure, including pollutant standards index (PSI), carbon monoxide (CO), nitric oxide (NO), nitric dioxide (NO₂), and nitrogen oxide (NOx) during pregnancy were all positively associated with KD incidence. Conversely, ozone (O₃) exposure had a negative correlation. Exposure to CO, NO, NO_2, and NOx after childbirth remained consistent with regards to having a positive association with KD incidence. Exposure to PSI and O₃ after delivery displayed no significant association with KD. Both prenatal and postnatal cumulative CO, NO, NO₂, and NOx exposure had a dose dependent effect towards increasing KD incidence. Certain prenatal and early life air pollutant exposure may increase the incidence of KD.

Assessment of Pediatric Admissions for Kawasaki Disease or Infectious Disease During the COVID-19 State of Emergency in Japan

IMPORTANCE

The development of Kawasaki disease (KD) has been suggested to be associated with droplet- or contact-transmitted infection; however, its triggers and transmission modes remain to be determined. Under an epidemic of SARS-CoV-2, the COVID-19 state of emergency in Japan served as a nationwide social experiment to investigate the impact of quarantine or isolation on the incidence of KD.

OBJECTIVE

To assess the role of droplet or contact transmission in the etiopathogenesis of KD.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, longitudinal, cross-sectional study was conducted from 2015 to 2020 at Fukuoka Children's Hospital and 5 adjacent general hospitals. The number of admissions for KD and infectious diseases were analyzed. Participants were pediatric patients admitted to the participating hospitals for KD or infectious diseases.

EXPOSURES

Quarantine and isolation owing to the COVID-19 state of emergency.

MAIN OUTCOMES AND MEASURES

The primary end points were the ratios of patients with KD to patients with respiratory tract or gastrointestinal infections admitted from April to May in 2015 to 2019 and 2020. A Poisson regression model was used to analyze them.

RESULTS

The study participants included 1649 patients with KD (median [interquartile range] age, 25 [13-43] months; 901 boys [54.6%]) and 15 586 patients with infectious disease (data on age and sex were not available for these patients). The number of admissions for KD showed no significant change between April and May in 2015 to 2019 vs the same months in 2020 (mean [SD], 24.8 [5.6] vs 18.0 [4.0] admissions per month; 27.4% decrease; adjusted incidence rate ratio [aIRR], 0.73; 95% CI, 0.48-1.10; P = .12). However, the number of admissions for droplet-transmitted or contact-transmitted respiratory tract infections (mean [SD], 157.6 [14.4] vs 39.0 [15.0] admissions per month; 75.3% decrease; aIRR, 0.25; 95% CI, 0.17-0.35; P < .001) and gastrointestinal infections (mean [SD], 43.8 [12.9] vs 6.0 [2.0] admissions per month; 86.3% decrease; aIRR, 0.14; 95% CI, 0.04-0.43; P < .001) showed significant decreases between April and May in 2015 to 2019 vs the same months in 2020 (total, 12 254 infections). Thus, the ratio of KD to droplet- or contact-transmitted respiratory tract and gastrointestinal infections incidence in April and May 2020 was significantly increased (ratio, 0.40 vs 0.12; χ21 = 22.76; P < .001).

CONCLUSIONS AND RELEVANCE

In this study, the significantly increased incidence of KD compared with respiratory tract and gastrointestinal infections during the COVID-19 state of emergency suggests that contact or droplet transmission is not a major route for KD development and that KD may be associated with airborne infections in most cases.

Is Short-Term Exposure to PM2.5 Relevant to Childhood Kawasaki Disease?

Background: Kawasaki disease (KD) is an acute febrile vascular disease of unknown cause that affects the whole body. KD typically occurs in infants under the age of five and is found mainly in East Asian countries. Few studies have reported on the relationship between the pollutant PM_2.5 and KD, and the evidence remains irrelevant or insufficient. Objectives: We investigated the relationship between short-term exposure to PM_2.5 and KD hospitalizations using data from Ewha Womans University Mokdong Hospital, 2006 to 2016. Methods: We obtained data from the hospital EMR (electronic medical records) system. We evaluated the relationship between short-term exposure to PM_2.5 and KD hospitalizations using a case-crossover design. We considered exposures to PM_2.5 two weeks before the date of KD hospitalization. We analyzed the data using a conditional logistic regression adjusted for temperature and humidity. The effect size was calculated as a 10 μg/m³ increase in PM_2.5 concentration. We performed a subgroup analysis by sex, season, age group, and region. In the two-pollutants model, we adjusted SO₂, NO₂, CO, and O₃, but the effect size did not change. Results: A total of 771 KD cases were included in this study. We did not find any statistically significant relationship between PM_2.5 and children’s KD hospitalization (two-day moving average: odds ratio (OR) = 1.01, 95% confidence intervals (CI) = 0.95, 1.06; seven-day moving average: OR = 0.98, CI = 0.91, 1.06; 14-day moving average: OR = 0.93, CI = 0.82, 1.05). A subgroup analysis and two pollutant analysis also found no significant results. Conclusion: We did not find a statistically significant relationship between PM_2.5 and children’s KD hospitalizations. More research is needed to clarify the association between air pollution, including PM_2.5, and KD.

Epidemiology of Kawasaki Disease in Europe

Aim of the review: To review major epidemiological aspects of Kawasaki disease (KD) in Europe, describing demographic characteristics, revising its incidence along with time trends and geographic variations, and describing migration studies to provide clues about its etiology. Recent findings: The annual incidence of KD in Europe is about 10-15 per 100,000 children under 5 years old and seems to be relatively stable over time and space. Demographic characteristics are in line with those in other countries of the world, with a higher incidence in children from Asia and possibly North African origin. All studies performed across Europe found a coherent seasonal distribution of KD onset peaking from winter to early spring. This seasonal distribution was consistent over the years and suggests a climate-related environmental trigger. The occurrence of peaks during pandemics, microbiological findings and a possible link with southerly winds support the hypothesis of an airborne infectious agent. Neither other airborne agents such as pollutants or pollens nor urbanization and industrialization seem to have major effect on the etiology. Conclusion: Discrepancies in KD incidence rates across studies were due more to methodological differences, variation in definitions and awareness of the disease than a real increase in incidence. Genetic predisposition is undeniable in KD, but environmental factors seem to play a pivotal role. Several lines of evidence support a non-exclusive airborne infectious agent with a protective immune response by the host as a key factor in inducing the inflammatory cascade responsible for symptoms and complications.