Hemorrhagic fever with renal syndrome (HFRS) is a major rodent-borne zoonosis. Each year worldwide, 60,000–100,000 HFRS human cases are reported in more than seventy countries with almost 90% these cases occurring in China. Shaanxi Province in China has been among the most seriously affected areas since 1955. During 2009–2013, Shaanxi reported 11,400 human cases, the most of all provinces in China. Furthermore, the epidemiological features of HFRS have changed over time. Using long-term data of HFRS from 2005 to 2016, we carried out this retrospective epidemiological study combining ecological assessment models in Shaanxi. We found the majority of HFRS cases were male farmers who acquired infection in Guanzhong Plain, but the geographic extent of the epidemic has slowly spread northward. The highest age-specific attack rate since 2011 was among people aged 60–74 years, and the percentage of HFRS cases among the elderly increased from 12% in 2005 to 25% in 2016. We highly recommend expanding HFRS vaccination to people older than 60 years to better protect against the disease. Multivariate analysis revealed artificial area, cropland, pig and population density, GDP, and climate conditions (relative humidity, precipitation, and wind speed) as significant risk factors in the distribution of HFRS.

Few studies evaluating inapparent dengue virus (DENV) infections have been conducted in China. In 2013, a large outbreak of DENV occurred in the city of Zhongshan, located in Southern China, which provided an opportunity to assess the clinical spectrum of disease. During the outbreak, an investigation of 887 index case contacts was conducted to evaluate inapparent and symptomatic DENV infections. Post-outbreak, an additional 815 subjects from 4 towns with, and 350 subjects from 2 towns without reported autochthonous DENV transmission, as determined by clinical diagnosis, were evaluated for serological evidence of dengue IgG antibodies. Between July and November 2013, there were 19 imported and 809 autochthonous dengue cases reported in Zhongshan. Of 887 case contacts enrolled during the outbreak, 13 (1.5%) exhibited symptomatic DENV infection, while 28 (3.2%) were inapparent. The overall I:S ratio was 2.2:1 (95% CI: 1.1-4.2:1). Post-outbreak serological data showed that the proportion of DENV IgG antibody detection from the 4 towns with and the 2 towns without reported DENV transmission was 2.7% (95% CI: 1.6%-3.8%) and 0.6% (95% CI: 0-1.4%), respectively. The I:S ratio in the 3 towns where clinical dengue cases were predominately typed as DENV-1 was 11.0:1 (95% CI: 3.7-∞:1). The ratio in the town where DENV-3 was predominately typed was 1.0:1 (95% CI: 0.5-∞:1). In this cross-sectional study, data suggests a high I:S ratio during a documented outbreak in Zhongshan, Southern China. These results have important implications for dengue control, implying that inapparent cases might influence DENV transmission more than previously thought.

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In this cross-sectional seroepidemiological study we sought to examine the evidence for circulation of Rift Valley fever virus (RVFV) among herders in Madagascar and Kenya. From July 2010 to June 2012, we enrolled 459 herders and 98 controls (without ruminant exposures) and studied their sera (immunoglobulin G [IgG] and IgM through enzyme-linked immunosorbent assay [ELISA] and plaque reduction neutralization test [PRNT] assays) for evidence of previous RVFV infection. Overall, 59 (12.9%) of 459 herders and 7 (7.1%) of the 98 controls were positive by the IgG ELISA assay. Of the 59 ELISA-positive herders, 23 (38.9%) were confirmed by the PRNT assay (21 from eastern Kenya). Two of the 21 PRNT-positive study subjects also had elevated IgM antibodies against RVFV suggesting recent infection. Multivariate modeling in this study revealed that being seminomadic (odds ratio [OR] = 6.4, 95% confidence interval [CI] = 2.1–15.4) was most strongly associated with antibodies against RVFV. Although we cannot know when these infections occurred, it seems likely that some interepidemic RVFV infections are occurring among herders. As there are disincentives regarding reporting RVFV outbreaks in livestock or wildlife, it may be prudent to conduct periodic, limited, active seroepidemiological surveillance for RVFV infections in herders, especially in eastern Kenya.

Abstract. In 2000, an outbreak of Rift Valley fever virus (RVFV) occurred in the Kingdom of Saudi Arabia (KSA). Since then there have been sparse efforts to monitor for RVFV reemergence. During 2012, we enrolled 300 individuals with ruminant exposure and 50 age-group matched non-exposed controls in southwestern KSA, in a cross-sectional epidemiological study of RVFV. Sera from the participants were screened with an enzyme-linked immunosorbent assay (ELISA) for anti-RVFV IgG antibodies of which 39 (11.1%) were positive. Sixteen (41.0%) of those 39 were also positive by a plaque reduction neutralization assay (PRNT). The PRNT-positive subjects were further studied with an IgM ELISA and one was positive. No RVFV was detected in the 350 sera using real-time reverse transcription polymerase chain reaction. Contact with cattle (odds ratio [OR] = 3.16, 95% confidence interval [CI] 1.01, 9.90) and a history of chronic medical illness (OR = 6.41, 95% CI 1.75, 23.44) were associated with greater odds of RVFV seropositivity by PRNT. The IgM-positive participant was 36 years of age, and reported multiple risk factors for ruminant contact. Although these findings simply may be vestiges of the 2000 epidemic, KSA's frequent visits from pilgrims and importations of live animals from RVFV-endemic areas suggest that more comprehensive surveillance for imported RVFV virus in ruminants, mosquitoes, and travelers is imperative.