Spatiotemporal transmission and determinants of typhoid and paratyphoid fever in Hongta District, Yunnan Province, China.

BACKGROUND: Typhoid and paratyphoid fever are endemic in Hongta District and their prevalence, at 113 per 100,000 individuals, remains the highest in China. However, the exact sources of the disease and its main epidemiological characteristics have not yet been clearly identified. METHODS AND FINDINGS: Numbers of typhoid and paratyphoid cases per day during the period 2006 to 2010 were obtained from the Chinese Center of Disease Control (CDC). A number of suspected disease determinants (or their proxies), were considered for use in spatiotemporal analysis: these included locations of discharge canals and food markets, as well as socio-economic and environmental factors. Results showed that disease prevalence was spatially clustered with clusters decreasing with increasing distance from markets and discharge canals. More than half of the spatial variance could be explained by a combination of economic conditions and availability of health facilities. Temporal prevalence fluctuations were positively associated with the monthly precipitation series. Polluted hospital and residential wastewater was being discharged into rainwater canals. Salmonella bacteria were found in canal water, on farmland and on vegetables sold in markets. CONCLUSION: DISEASE TRANSMISSION IN HONGTA DISTRICT IS DRIVEN PRINCIPALLY BY TWO SPATIOTEMPORALLY COUPLED CYCLES: one involving seasonal variations and the other the distribution of polluted farmland (where vegetables are grown and sold in markets). Disease transmission was exacerbated by the fact that rainwater canals were being used for disposal of polluted waste from hospitals and residential areas. Social factors and their interactions also played a significant role in disease transmission.

[Burden of disease regarding paratyphoid fever A - based on the Syndromic Surveillance System on Fever].

OBJECTIVE: To evaluate the burden of paratyphoid fever A in Hongta district, Yuxi city, Yunnan province from May 1, 2008 to April 30, 2009 so as to provide information for the development of comprehensive intervention measures. METHODS: Based on the Fever Syndromic Surveillance System, information as attendance rate of patients with fever, rate of patients being sampled, laboratory testing rate, sensitivity on the detection of blood culture and the rate of case reporting etc. were calculated. According to the pyramid model of food-borne disease on disease burden, the local actual incidence of paratyphoid fever A was estimated and analyzed. RESULTS: Under the Fever Syndromic Surveillance System, there were 6642 fever cases being detected, among whom 6570 cases were sampled and undergone testing, with the sampling rate as 98.92% and all the samples received laboratory testing. There were 354 positive cases of paratyphoid fever A reported, all from the Hongta district. Data showed that the attendance rate of the feverish patients was 73.53%, with the highest rate seen in whose under 10 years old (100%). Assumed that the sensitivity of paratyphoid fever blood culture was 70%, and the case reporting rate was 90%, we estimated that the annual incidence of paratyphoid fever A in Hongta was 220.33 (95%CI: 170.1 - 521.4) per 100 thousand, with 965 (95%CI: 745 - 2284) as new cases. Among all the age groups, the incidence in the age group from 15 to 44 years old was estimated to be at the highest (318.27 per 100 thousand). CONCLUSION: Hongta seemed to be an endemic region for paratyphoid fever A, with the highest incidence occurred in the age group of between 15 and 44 years old. These findings highlighted the urgent need to carry out further investigation on the risk factors and to implement targeted effective prevention and control measures.

[Epidemiologie investigation on murine typhus in Hongta areas of Yuxi city, Yunnan province of China].

OBJECTIVE: To identify epidemic status of murine typhus in Hongta areas of Yuxi city and to provide evidence for control and prevention of the disease. METHODS: Serologic survey was conducted among residents and rodents. Isolation of Rickettsia moseri was performed. RESULTS: The overall infection rate among general population was 28.92% (96/332) with geometric meantiter (GMT) as 10.83 and there was no difference between males and females (26.71%, 43/161 vs. 30.99%, 53/171, P > 0.05). Significant differences were found between age groups (P < 0.05) with positive rates of 29.63% (8/27), 18.06% (13/72), 39.62% (42/106), 27.50% (22/80) and 23.40% (11/47) among age groups 0-6, 7-18, 19-39, 40-59 and over 60, respectively. The overall rate of infection in mouse was 44.95% (89/198) with GMT as 30.30. Five isolates of R. moseri from mouse specimen, three from fleas plus one case of murine typhus were diagnosed. Rattus norvegicus and Rattus flavipectus were the predominant species of rodent animals (99.49%, 197/198) and Xenopsylla cheopis was the major species of vector (74.26%, 303/408). Flea index and mouse density were 2.06 and 11.13% respectively. CONCLUSION: High infection rates on R. moseri were demonstrated in rodents and residents as well as high risk of murine typhus outbreak might occur in these areas.