Impact of Temperature and Rainfall on Typhoid/Paratyphoid Fever in Taizhou, China: Effect Estimation and Vulnerable Group Identification

Abstract

The impact of temperature and rainfall on the occurrence of typhoid/paratyphoid fever are not fully understood. This study aimed to characterize the effect of daily ambient temperature and total rainfall on the incidence of typhoid/paratyphoid in a sub-tropical climate city of China and to identify the vulnerable groups for disease prevention. Daily notified typhoid/paratyphoid fever cases and meteorological data for Taizhou from 2005 to 2013 were extracted from the National Notifiable Disease Surveillance System and the Meteorological Data Sharing Service System, respectively. Distributed lag nonlinear model was used to quantify the association between daily mean temperature, total rainfall, and typhoid/paratyphoid fever. Subgroup analyses by gender, age, and occupation were conducted to identify the vulnerable groups. A total of 625 typhoid fever cases and 1,353 paratyphoid fever cases were reported during the study period. An increased risk of typhoid fever was detected with the increase of temperature (Each 2°C rise resulted in 6%, 95% [confidence interval] CI: 2-10% increase in typhoid cases), while the increased risk was associated with the higher temperature for paratyphoid (the highest cumulative risk of temperature was 33.40 [95% CI: 12.23-91.19] at 33°C). After the onset of mild precipitation, the relative risk of typhoid fever increased in a short-lasting and with a 13-26 days delay, and the risk was no significant after the continuous increase of precipitation (the highest cumulative risk of rainfall was 24.96 [95% CI: 4.54-87.21] at 100 mm). Whereas the risk of paratyphoid fever was immediate and long lasting, and increase rapidly with the increase of rainfall (each 100 mm increase was associated with 26% increase in paratyphoid fever cases). Significant temperature-typhoid/paratyphoid fever and rainfall-typhoid/paratyphoid fever associations were found in both genders and those aged 0-4 years old, 15-60 years old, farmers, and children. Characterized with a lagged, nonlinear, and cumulative effect, high temperature and rainfall could increase the risk of typhoid/paratyphoid fever in regions with a subtropical climate. Public health interventions such as early warning and community health education should be taken to prevent the increased risk of typhoid/paratyphoid fever, especially for the vulnerable groups.

Figure 1.

Location of Taizhou in Zhejiang Province, China. This figure appears in color at www.ajtmh.org.

Figure 2.

The distribution of daily typhoid/paratyphoid fever cases, daily mean temperature and daily total rainfall from 2005 to 2013 in Taizhou, China.

Figure 3.

Lagged and cumulative association between temperature/rainfall and typhoid fever. The three-dimensional effects diagram of the daily average temperature on typhoid fever at the lag of 7–30 days (A), Predictor-specific effects of temperature 20°C on typhoid fever (B), Lag-specific effects between temperature and typhoid fever at lag 20 days (C), the overall cumulative effects of daily average temperature on typhoid fever (D), The three-dimensional effects diagram of the daily total precipitation on typhoid fever at the lag of 7–30 days (E), Predictor-specific effects of precipitation 100 mm on typhoid fever (F), Lag-specific effects between precipitation and typhoid fever at lag 20 days (G), the overall cumulative effects of daily average temperature on typhoid fever (H), Taizhou, China, 2005–2013. This figure appears in color at www.ajtmh.org.

Figure 4.

Lagged and cumulative association between temperature/rainfall and paratyphoid fever. The three-dimensional effects diagram of the daily average temperature on paratyphoid fever at the lag of 3–20 days (A), Predictor-specific effects of temperature 20°C on paratyphoid fever (B), Lag-specific effects between temperature and paratyphoid fever at lag 10 days (C), the overall cumulative effects of daily average temperature on paratyphoid fever (D), The three-dimensional effects diagram of the daily total precipitation on paratyphoid fever at the lag of 3–20 days (E), Predictor-specific effects of precipitation 100 mm on paratyphoid fever (F), Lag-specific effects between precipitation and typhoid fever at lag 10 days (G), the overall cumulative effects of daily average temperature on paratyphoid fever (H), Taizhou, China, 2005–2013. This figure appears in color at www.ajtmh.org.

Figure 5.

The fraction of typhoid/paratyphoid fever morbidity attribute to temperature/rainfall among different subgroups. This figure appears in color at www.ajtmh.org.