Abstract
Background: Scrub typhus was epidemic in the western Pacific Ocean area and East Asia, scrub typhus epidemic in densely populated areas in southern China. To better understand the association between meteorological variables, Southern Oscillation Index (SOI), and scrub typhus incidence in Guangzhou was benefit to the control and prevention.Methodology/Principal Findings: We collected weekly data for scrub typhus cases and meteorological variables in Guangzhou, and Southern Oscillation Index from 2006 to 2018, and used the distributed lag non-linear models to evaluate the relationships between meteorological variables, SOI and scrub typhus. The median value of each variable was set as the reference. The high-risk occupations were farmer (51.10%), house worker (17.51%), and retiree (6.29%). The non-linear relationships were observed with different lag weeks. For example, when the mean temperature was 27.7°C with1-week lag, the relative risk (RR) was highest as 1.08 (95% CI: 1.01–1.17). The risk was the highest when the relative humidity was 92.0% with 9-week lag, with the RR of 1.10 (95% CI: 1.02–1.19). For aggregate rainfall, the highest RR was 1.06 (95% CI: 1.03–1.11), when it was 83.0 mm with 4-week lag. When the SOI was 19 with 11-week lag, the highest RR was 1.06 (95% CI: 1.01–1.12). Most of the extreme effects of SOI and meteorological factors on scrub typical cases were statistically significant.Conclusion/Significance: The high-risk occupations of scrub typhus in Guangzhou were farmer, house worker, and retiree. Meteorological factors and SOI played an important role in scrub typhus occurrence in Guangzhou. Non-linear relationships were observed in almost all the variables in our study. Approximately, mean temperature, and relative humidity positively correlated to the incidence of scrub typhus, on the contrary to atmospheric pressure and weekly temperature range (WTR). Aggregate rainfall and wind velocity showed an inverse-U curve, whereas the SOI appeared the bimodal distribution. These findings can be helpful to facilitate the development of the early warning system to prevent the scrub typhus.
Highlights
Scrub typhus, a rickettsiosis caused by Orientia tsutsugamushi, is epidemic in the western Pacific Ocean area and East Asia [1, 2]
The laboratory confirmed cases must meet the criteria mentioned above and fulfill one of the following criteria: fourfold or more increase in serum IgG antibody titers between acute and convalescent sera-detected by indirect immune fluorescence antibody assay (IFA); The O. tsutsugamushi was detected in clinical specimens using polymerase chain reaction (PCR); the isolation of O. tsutsugamushi [19]
During 2006–2018, 84.76% (7,073) cases occurred from May to October, with the peak at June. (Figure 1) during the study period, Table 1 showed the weekly distribution of meteorological variables, Southern Oscillation Index (SOI) and scrub typhus cases
Summary
Scrub typhus (tsutsugamushi disease), a rickettsiosis caused by Orientia tsutsugamushi, is epidemic in the western Pacific Ocean area and East Asia [1, 2]. Scrub typhus cases showed a rising trend in Asia, case-fatality rates from areas with reduced drug sensitivity were reported in South India and northern Thailand at 12.2 and 13.6%, respectively [3], and it has become an important health issue in China [4]. Scrub typhus epidemic in densely populated areas in southern China and millions of people is at risk of the infection of scrub typhus [5]. Scrub typhus was epidemic in the western Pacific Ocean area and East Asia, scrub typhus epidemic in densely populated areas in southern China. To better understand the association between meteorological variables, Southern Oscillation Index (SOI), and scrub typhus incidence in Guangzhou was benefit to the control and prevention
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