The Temporal Lagged Relationship Between Meteorological Factors and Scrub Typhus With the Distributed Lag Non-linear Model in Rural Southwest China

Rapid changes in warm and cold extremes in recent decades and their future projections for India

Assessing changes in temperature extremes is essential for understanding the impacts of global warming on agriculture and public health in a populous and developing country like India. This study analyses trends in warm and cold extremes using surface observations (1980-2020) and Coupled Model Intercomparison Project Phase 6 (CMIP6) data. We find a significant increase in warm days (2-7 days/decade) and warm nights (2-8 days/decade) across India, particularly in the Northeast (NE), Northwest, and Peninsular (IP) regions during 1980-2020. Concurrently, cold days (-3 to -1 days/decade) and cold nights (-1 to -5 days/decade) have decreased in the same period. The frequency of warm days (3 ± 0.8 days/dec) has increased at a slightly higher rate than that of warm nights (2 ± 1 days/dec), which is consistent with the decrease in cold days (-1.8 ± 0.8 days/dec) and cold nights (-2±0.8 days/dec) in 1980-2020, and it is three-fold in NE and IP (-2 to -7 days/dec) in winter. Future projections under the high emission SSP5-8.5 scenario indicate a five-fold increase in warm days and nights, alongside a four-to six-fold reduction in cold days and nights by 2080-2100. Our analysis unfolds the severe warming in India and its potential to trigger more extreme weather events, regional climate change, and associated natural disasters such as frequent heat waves. These changes can have substantial implications for crop yields, heat stress, and energy demand.

Meteorological factors and normalized difference vegetation index drivers of scrub typhus incidence in Shandong Province based on a 16-year time-frequency analysis

OBJECTIVE

Scrub typhus, a natural epidemic disease that seriously impacts the health of the population, has imposed a substantial disease burden in Shandong Province. This study aimed to determine the periodicity of the scrub typhus incidence and identify the environmental risk factors affecting scrub typhus to help prevent and control its occurrence in Shandong Province.

METHODS

Monthly cases of scrub typhus, mean air temperature, relative humidity, cumulative precipitation, and Normalized Difference Vegetation Index (NDVI) data in Shandong Province from 2006 to 2021 were collected. Wavelet analysis was used to determine the incidence period of scrub typhus and to explore the relationships between environmental factors and the incidence of scrub typhus. Additionally, partial wavelet coherence (PWC) was employed to identify whether meteorological factors affect the association between NDVI and scrub typhus incidence.

RESULTS

Our results showed that scrub typhus incidence has a predominantly one-year period, followed by a less powerful six-month period. The wavelet coherence results revealed positive correlations between scrub typhus incidence and temperature, precipitation, relative humidity, and NDVI. Meteorological factors had a lagged effect of approximately 1-2 months (The phase angles of temperature, precipitation, and relative humidity were 59.15°, 56.57°, and 47.17° respectively) on scrub typhus incidence, whereas NDVI showed a lagged effect of approximately 1-2 weeks (The phase angle of NDVI was 18.11°). On the basis of partial wavelet analysis, we found that temperature and precipitation affected the association between NDVI and scrub typhus incidence.

CONCLUSION

Meteorological factors and NDVI play important roles in the occurrence of scrub typhus in Shandong Province. Moreover, temperature and precipitation can affect the role of NDVI. This study provides valuable recommendations and resources for the timely detection, mitigation, and management of scrub typhus in Shandong Province.

Exploring the effects and interactions of meteorological factors on the incidence of scrub typhus in Ganzhou City, 2008-2021

BACKGROUND

Scrub typhus poses a substantial risk to human life and wellbeing as it is transmitted by vectors. Although the correlation between climate and vector-borne diseases has been investigated, the impact of climate on scrub typhus remains inadequately comprehended. The objective of this study is to investigate the influence of meteorological conditions on the occurrence of scrub typhus in Ganzhou City, Jiangxi Province.  METHODS: From January 1, 2008 to December 31, 2021, we gathered weekly records of scrub typhus prevalence alongside meteorological data in Ganzhou city. In order to investigate the correlation between meteorological factors and scrub typhus incidence, we utilized distributional lag nonlinear models and generalized additive models for our analysis.

RESULTS

Between 2008 and 2021, a total of 5942 cases of scrub typhus were recorded in Ganzhou City. The number of females affected exceeded that of males, with a male-to-female ratio of 1:1.86. Based on the median values of these meteorological factors, the highest relative risk for scrub typhus occurrence was observed when the weekly average temperature reached 26 °C, the weekly average relative humidity was 75%, the weekly average sunshine duration lasted for 2 h, and the weekly mean wind speed measured 2 m/s. The respective relative risks for these factors were calculated as 3.816 (95% CI: 1.395-10.438), 1.107 (95% CI: 1.008-1.217), 2.063 (95% CI: 1.022-4.165), and 1.284 (95% CI: 1.01-1.632). Interaction analyses showed that the risk of scrub typhus infection in Ganzhou city escalates with higher weekly average temperature and sunshine duration.

CONCLUSION

The findings of our investigation provide evidence of a correlation between environmental factors and the occurrence of scrub typhus. As a suggestion, utilizing environmental factors as early indicators could be recommended for initiating control measures and response strategies.

Epidemiological and clinical characteristics of scrub typhus in northern Fujian, China, from 2015 to 2019

BACKGROUND

This study aimed to analyze the epidemiological and clinical characteristics of scrub typhus in northern Fujian Province on the southeast coast of China.

METHODS

A retrospective analysis was performed on 303 patients with scrub typhus admitted to the First Hospital of Nanping City, Fujian Province, from January 2015 to December 2019. The epidemic characteristics were analyzed, such as the annual number of cases, age distribution, sex distribution, and seasonal distribution in each region. The patient's clinical manifestations, signs, complications, auxiliary examinations, and prognosis were analyzed.

RESULTS

From 2015 to 2019, the age distribution of scrub typhus cases was mainly concentrated in 40-49 y (17.16%), 50-59 y (24.09%), and 60-69 y (26.73%). There were no sex differences among the patients. 68.98% of the cases were concentrated in rural areas, with farmers having the highest proportion. However, this study compared prognostic factors in the cured and uncured groups, and found significant differences in non-farmer occupation and diagnosis time ≥ 8 days. Scrub typhus showed two peaks north of Fujian; the prominent peak was from June to July, and the other slight rise was from October to November. The SDE plot showed that the cases were mainly concentrated in Yanping, Shunchang, Zhenghe, and Songxi counties. The number of cases in hilly and mountainous areas was higher than in plain areas. The main diagnostic methods in this area are based on specific eschar and epidemiology, while the positive rate of the Weil-Felix test is low.

CONCLUSIONS

The results of this study can guide primary care institutions to improve the level of diagnosis and treatment of scrub typhus and take effective public health intervention measures in endemic areas.