BackgroundTo describe the epidemiologic profile and trends of imported malaria, and to identify the populations at risk of malaria in China during 2010–2014.MethodsThis is a descriptive analysis of laboratory confirmed malaria cases during 2010–2014. Data were obtained from surveillance reports in the China Information System for Disease Control and Prevention (CISDCP). The distribution of imported malaria cases over the years was analysed with X2 for trend analysis test. All important demographic and epidemiologic variables of imported malaria cases were analysed.ResultsMalaria incidence in general reduced greatly in China, while the proportion of Plasmodium falciparum increased threefold from 0.08 to 0.21 per 100,000 population during the period 2010–2014. Of a total 17,725 malaria cases reported during the study period, 11,331 (64 %) were imported malaria and included an increasing trend: 292 (6 %), 2103 (63 %), 2151 (84 %), 3881 (96 %), 2904 (97 %), respectively, (X2 = 2110.70, p < 0.01). The majority of malaria cases (imported and autochthonous) were adult (16,540, 93 %), male (15,643, 88 %), and farming as an occupation (11,808, 66 %). Some 3027 (94 %) of imported malaria cases had labour-related travel history during the study period; 90 % (6340/7034) of P. falciparum infections were imported into China from Africa, while 77 % of Plasmodium vivax infections (2440/3183) originated from Asia.ConclusionsMalaria elimination in China faces the challenge of imported malaria, especially imported P. falciparum. Malaria prevention activities should target exported labour groups given the increasing number of workers returning from overseas.

BackgroundWith the dramatic increase in international travel among Chinese people, the risk of malaria importation from malaria-endemic regions threatens the achievement of the malaria elimination goal of China.MethodsEpidemiological investigations of all imported malaria cases were conducted in nine provinces of China from 1 Nov, 2013 to 30 Oct, 2014. Plasmodium species, spatiotemporal distribution, clinical severity, preventive measures and infection history of the imported malaria cases were analysed using descriptive statistics.ResultsA total of 1420 imported malaria cases were recorded during the study period, with P. falciparum (723 cases, 50.9 %) and P. vivax (629 cases, 44.3 %) being the two predominant species. Among them, 81.8 % of cases were in Chinese overseas labourers. The imported cases returned from 41 countries, mainly located in Africa (58.9 %) and Southeast Asia (39.4 %). About a quarter (25.5 %, 279/1094) of counties in the nine study provinces were affected by imported malaria cases. There were 112 cases (7.9 %) developing complicated malaria, including 12 deaths (case fatality rate: 0.8 %). Only 27.8 % of the imported cases had taken prophylactic anti-malarial drugs. While staying abroad, 27.7 % of the cases had experienced two or more episodes of malaria infection. The awareness of clinical manifestations and the capacity for malaria diagnosis were weak in private clinics and primary healthcare facilities.ConclusionsImported malaria infections among Chinese labourers, returned from various countries, poses an increasing challenge to the malaria elimination programme in China. The risk of potential re-introduction of malaria into inland malaria-free areas of China should be urgently addressed.

Background Substantial outbreaks of scrub typhus, coupled with the discovery of this vector-borne disease in new areas, suggest that the disease remains remarkably neglected. The objectives of this study were to map the contemporary and potential transmission risk zones of the disease and to provide novel insights into the health burden imposed by scrub typhus in southern China. Methods Based on the assembled data sets of annual scrub typhus cases and maps of environmental and socioeconomic correlates, a boosted regression tree modeling procedure was used to identify the environmental niche of scrub typhus and to predict the potential infection zones of the disease. Additionally, we estimated the population living in the potential scrub typhus infection areas in southern China. Results Spatiotemporal patterns of the annual scrub typhus cases in southern China between 2007 and 2017 reveal a tremendous, wide spread of scrub typhus. Temperature, relative humidity, elevation, and the normalized difference vegetation index are the main factors that influence the spread of scrub typhus. In southern China, the predicted highest transmission risk areas of scrub typhus are mainly concentrated in several regions, such as Yunnan, Guangxi, Guangdong, Hainan, and Fujian. We estimated that 162 684 million people inhabit the potential infection risk zones in southern China. Conclusions Our results provide a better understanding of the environmental and socioeconomic factors driving scrub typhus spread, and estimate the potential infection risk zones beyond the disease’s current, limited geographical extent, which enhances our capacity to target biosurveillance and help public health authorities develop disease control strategies.

S crub typhus is a life-threatening disease caused by Orientia tsutsugamushi, an obligate intracellular bacterium transmitted by the larvae of trombiculid mites (1). Only biting larvae of Asian scrub typhus chiggers (Leptotrombidium spp.) can transmit the disease. After the bite of an infective mite, a characteristic necrotic inoculation lesion (an eschar) can develop. The microorganism then spreads through the lymphatic fluid and blood, causing manifestations including fever, headache, rash, lymphadenopathy, and mental changes (1). Without appropriate treatment with specific antimicrobial drugs (e.g., tetracycline, chloramphenicol, doxycycline, or azithromycin), >6% of infected patients will die (2,3). There is no licensed human vaccine to prevent scrub typhus infection. Globally, scrub typhus is traditionally regarded as a disease endemic to a region called the Asia-Pacific tsutsugamushi triangle, which extends from Pakistan in the west to far eastern Russia in the east to northern Australia in the south. In some countries of Southeast Asia, scrub typhus is a leading cause of treatable nonmalarial febrile illness (4-6). It is estimated that scrub typhus threatens >1 billion persons, causes at least 1 million clinical cases per year, and is associated with substantial mortality rates globally (1,7). The 2010s saw a widespread reemergence of scrub typhus in endemic regions such as India, Korea, Laos, and the Maldives (3,6,8). The recent emergence of scrub typhus in the Arabian Peninsula, Chile, and possibly Kenya suggests wider global distribution of this disease in tropical and subtropical regions, far from the tsutsugamushi triangle (9-12). Although scrub typhus poses the greatest threat to residents of eastern and southern Asia as well as tourists traveling to these regions, it remains a neglected disease globally. The lack of both research and a nationwide surveillance system within many endemic regions have resulted in poorly understood epidemiologic characteristics and disease burden of scrub typhus at global, national, and subnational levels (7). The Global Burden of Disease Study publishes estimates for 333 diseases and injuries, but currently bundles scrub typhus with other neglected tropical diseases, rather than providing specific burden estimates (13). In China, scrub typhus cases were recorded in the early 1950s, and a disease surveillance system for scrub typhus was established in 1952 (14,15). Leptotrombidium deliense and L. scutellare mites are the 2 principal vectors transmitting the disease in the country (16). L. deliense mites inhabit southern China and emerge in April, peaking in June-August, and decreasing

Background The relative contributions of asymptomatic, pre-symptomatic and symptomatic transmission of SARS-CoV-2 have not been clearly measured although control measures may differ in response to the risk of spread posed by different types of cases. Methods We collected detailed information on transmission events and symptom status based on laboratory-confirmed patient data and contact tracing data from four provinces and one municipality in China. We estimated the variation in risk of transmission over time, and the severity of secondary infections, by symptomatic status of the infector. Results There were 393 symptomatic index cases with 3136 close contacts and 185 asymptomatic index cases with 1078 close contacts included into the study. The secondary attack rate among close contacts of symptomatic and asymptomatic index cases were 4.1% (128/3136) and 1.1% (12/1078), respectively, corresponding to a higher transmission risk from symptomatic cases than from asymptomatic cases (OR: 3.79, 95% CI: 2.06, 6.95). Approximately 25% (32/128) and 50% (6/12) of the infected close contacts were asymptomatic from symptomatic and asymptomatic index cases, respectively, while more than one third (38%) of the infections in the close contacts of symptomatic cases were attributable to exposure to the index cases before symptom onset. Infected contacts of asymptomatic index cases were more likely to be asymptomatic and less likely to be severe. Conclusions Asymptomatic and pre-symptomatic transmission play an important role in spreading infection, although asymptomatic cases pose a lower risk of transmission than symptomatic cases. Early case detection and effective test-and-trace measures are important to reduce transmission.