Investigation on the epidemic factors of scrub typhus in Fuyang city, Anhui province in 2008.

Objective To identify the risk factors of scrub typhus and provide the basis for prevention and control of this disease. Methods A case-control study was conducted to identify the risk factors of the scrub typhus epidemic in the city. All clinically diagnosed cases and confirmed cases were included as the case group. For each patient, two controls were randomly selected from the symptom-free villagers with the same sex and an age gap of smaller than 5 years in the same village. The data were inputted into EpiData 3.1 and analyzed using conditional logistic regression model in SPSS 17.0. Results A total of 78 scrub typhus cases were found, including 16 laboratory-confirmed cases, 34 clinically diagnosed cases and 28 suspected cases. The 1∶M multiple conditional logistic regression analysis showed that sowing and harvest was the risk factor of this epidemic (OR=6.33, 95%CI:1.12-37.25). Further analysis showed that 51.6% patients and 22.8% of the control subjects had took part in the harvest of soybeans, a risk factor of scrub typhus (OR=3.62, 95%CI:1.36-9.59). However, the relationship between this epidemic and corn harvest and wheat sowing was not evident (P0.05). Conclusion The event was an epidemic of scrub typhus among farmers due to bites of mite larvae during unprotected harvest of soybeans.