How meteorological factors impacting on scrub typhus incidences in the main epidemic areas of 10 provinces, China, 2006–2018

Abstract

Scrub typhus, caused by Orientia tsutsugamushi, is a serious public health problem in the Asia-Pacific region, threatening the health of more than one billion people. China is one of the countries with the most serious disease burden of scrub typhus. Previous epidemiological evidence indicated that meteorological factors may affect the incidence of scrub typhus, but there was limited evidence for the correlation between local natural environment factors dominated by meteorological factors and scrub typhus. This study aimed to evaluate the correlation between monthly scrub typhus incidence and meteorological factors in areas with high scrub typhus prevalence using a distributed lag non-linear model (DLNM). The monthly data on scrub typhus cases in ten provinces from 2006 to 2018 and meteorological parameters were obtained from the Public Health Science Data Center and the National Meteorological Data Sharing Center. The results of the single-variable and multiple-variable models showed a non-linear relationship between incidence and meteorological factors of mean temperature (Tmean), rainfall (RF), sunshine hours (SH), and relative humidity (RH). Taking the median of meteorological factors as the reference value, the relative risks (RRs) of monthly Tmean at 0°C, RH at 46%, and RF at 800 mm were most significant, with RRs of 2.28 (95% CI: 0.95–5.43), 1.71 (95% CI: 1.39–2.09), and 3.33 (95% CI: 1.89–5.86). In conclusion, relatively high temperature, high humidity, and favorable rainfall were associated with an increased risk of scrub typhus.

The impact of meteorological parameters on the scrub typhus incidence in Baoshan City, western Yunnan, China

“…In addition, this study also indicated that increased monthly minimum temperature could lead to high risk of the occurrence of scrub typhus. This result is consistent with previous study showing that mite activity decreases when the temperature drops below 10°C ( 21 ). In southern Yunnan, L. deliense is the summer-autumn type, with the highest numbers in July ( 38 ).…”

“…Female mites mainly deposit their eggs from March to May, with egg-laying rates decreasing when the temperature ranges rise between 25 and 30°C ( 30 ). The optimal temperature for larva hatching and development is above 22°C, and temperatures between 18 and 30°C are conducive for mites to seek hosts for pathogen transmission ( 21 , 30 , 35 , 36 ). Adult mites remain in the soil for at least 15 months, while the larva stage can survive several months until the appropriate temperature for feeding ( 29 ).…”

Epidemiological and clinical characteristics of scrub typhus in Guizhou Province, China: An outbreak study of scrub typhus

“…Without appropriate treatment, the mortality rate of patients with ST may be as high as 30–70%, while the median mortality rate of untreated patients is 6%, compared to 1.4% for those who receive treatment [ 5 ]. In China, scrub typhus is mainly endemic in the north, south and southwest of the country [ 6 ], which includes the Guangdong, Yunnan, Anhui, Guangxi, Fujian, Jiangsu, Shandong and Jiangxi provinces [ 7 ].…”

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

“…The incidence rate of scrub typhus in Jiangxi Province from 2006 to 2012 demonstrated a consistent upward trend [ 12 ]. Additionally, there were a total of eight provinces in mainland China that reported more than 5000 cases of scrub typhus between 2006 and 2018, with Jiangxi Province being one of them [ 13 ]. Since the first case was reported in Ganzhou City in 2006, the disease has been spreading, making it a high prevalence area for scrub typhus in Jiangxi Province [ 14 ].…”