Effects of Climate and Rodent Factors on Hemorrhagic Fever with Renal Syndrome in Chongqing, China, 1997–2008

<div><p>China has the highest global incidence of hemorrhagic fever with renal syndrome (HFRS), constituting 90% of the cases in the world. Chongqing, located in the Three Gorges Reservoir Region, has been experiencing differences in the occurrence of HFRS from 1997 to 2008. The current study was designed to explore the effects of climate and rodent factors on the transmission of HFRS in Chongqing. Data on monthly HFRS cases, rodent strains, and climatic factors were collected from 1997 to 2008. Spatio-temporal analysis indicated that most HFRS cases were clustered in central Chongqing and that the incidence of HFRS decreased from 1997 to 2008. Poisson regression models showed that temperature (with lagged months of 0 and 5) and rainfall (with 2 lagged months) were key climatic factors contributing to the transmission of HFRS. A zero-inflated negative binomial model revealed that rodent density was also significantly associated with the occurrence of HFRS in the Changshou district. The monthly trend in HFRS incidence was positively associated with rodent density and rainfall and negatively associated with temperature. Possible mechanisms are proposed through which construction of the dam influenced the incidence of HFRS in Chongqing. The findings of this study may contribute to the development of early warning systems for the control and prevention of HFRS in the Three Gorges Reservoir Region.</p></div

Rodent strain and zero-inflated model in the Changshou district from 1997 to 2007.

<p>Zero-inflated model showed that the coefficient of rodent density was significantly positive in the negative binomial regression part but not significant in the zero inflation (logistic regression) part, indicating an overall positive association between the HFRS incidence and rodent density.</p

Temporal pattern of HFRS occurrence from 1997 to 2008.

<p>(A) Annual and monthly trends of HFRS incidence in the study area; (B) Seasonal trend of HFRS incidence in the study area. HFRS: hemorrhagic fever with renal syndrome. Case numbers for each month are presented as mean ± standard error of mean.</p

Spatial distribution of HFRS occurrence from 1997 to 2008.

<p>WS: Wushan; FJ: Fengjie; YY: Yunyang; KX: Kaixian; WZ: Wanzhou; SZ: Shizhu; ZX: Zhongxian; FD: Fengdu; WL: Wulong; FL: Fuling; CS: Changshou; YB: Yubei; BN: Banan. TGD: Three Gorges Dam. HFRS: hemorrhagic fever with renal syndrome. Central region includes the districts of ZX, CS, SZ, FL, FD, and WL. The rest of districts are designated as periphery region.</p

Association between climatic factors and HFRS incidence in Chongqing City from 1997 to 2008, analyzed by Poisson regression models.

<p>HFRS: hemorrhagic fever with renal syndrome; GDP: gross domestic product; Lx: the lagged months.</p><p>Association between climatic factors and HFRS incidence in Chongqing City from 1997 to 2008, analyzed by Poisson regression models.</p

Comparison of climatic factors between central and periphery regions from 1997 to 2008.

<p>(A) Difference in annual temperatures between central and periphery regions; (B) Difference in annual precipitations between central and periphery regions.</p

Proposed mechanisms of TGD-associated HFRS occurrence.

<p>The occurrence of HFRS involves multiple factors including climate factors, rodent factors and social activities. Climate factors and social activities can affect hantavirus transmission directly or indirectly through changing rodent dynamics. Although the effects of dam construction on the social activities have been reported, whether the dam affects HFRS occurrence through changing local climate and/or rodent dynamics remains elusive. TGD: Three Gorges Dam. HFRS: hemorrhagic fever with renal syndrome. HV: hantavirus. GDP: gross domestic product.</p

Epidemiological and Virological Characteristics of Influenza in Chongqing, China, 2011-2015

<div><p>Background</p><p>Chongqing is the largest municipality and located in Southwestern of China, with over 30 million registered inhabitants. There are few reports regarding the epidemiology of influenza in Chongqing. The objective of the paper is to explore the epidemiology of influenza in Chongqing, in order to provide scientific basis for prevention and control of influenza.</p><p>Methodology /Principal Findings</p><p>From 2011 to 2015, we collected information on influenza-like illness (ILI) patients fulfilling the case definition, and took nasalpharyngeal or throat swabs specimens from ILI cases per week at the 7 sentinel hospitals. Specimens were tested by reverse transcription-polymerase chain reaction(RT-PCR) for influenza. Descriptive epidemiology was applied to analyze the epidemiology and etiology of influenza. A total of 9,696,212 cases were enrolled, of which 111,589 were ILI. Of those 24,868 samples from ILI cases, 13.3% (3,314/24,868) tested positive for influenza virus (65.7% influenza A, 34.1% influenza B, and 0.2% influenza A and B co-infection). Among the influenza A viruses, 71.3% were seasonal influenza A(H3N2) and 28.7% were influenza A(H1N1)pdm09. No cases of seasonal A(H1N1) were detected. The isolation rate was highest in children aged 5–14 years old. Influenza activity consistently peaked during January-March in 2011–2015, and June-July in 2012, 2014 and 2015.</p><p>Conclusions</p><p>Influenza is an important public health problem among ILI patients in Chongqing, especially among school-aged children. It might be beneficial to prioritize influenza vaccination for school-aged children and implement the school-based intervention to prevent and mitigating influenza outbreaks in Chongqing, particularly during the seasonal peaks.</p></div

Age distribution of influenza virus types and subtypes.

<p>Age distribution of influenza virus types and subtypes.</p

The weekly distribution of influenza-like illness, 2011–2015.

<p>The weekly distribution of influenza-like illness, 2011–2015.</p