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Michael Novakhov – SharedNewsLinks: From environmental variability to disease prevention largely based on data from China | ||||
AbstractHantaviruses can cause hantavirus pulmonary syndrome (HPS) in the Americas and hemorrhagic fever with renal syndrome (HFRS) in Eurasia. In recent decades, repeated outbreaks of hantavirus disease have led to public concern and have created a global public health burden. Hantavirus spillover from natural hosts into human populations could be considered an ecological process, in which environmental forces, behavioral determinants of exposure, and dynamics at the humananimal interface affect human susceptibility and the epidemiology of the disease. In this review, we summarize the progress made in understanding hantavirus epidemiology and rodent reservoir population biology. We mainly focus on three species of rodent hosts with longitudinal studies of sufficient scale: the striped field mouse (Apodemus agrarius, the main reservoir host for Hantaan virus [HTNV], which causes HFRS) in Asia, the deer mouse (Peromyscus maniculatus, the main reservoir host for Sin Nombre virus [SNV], which causes HPS) in North America, and the bank vole (Myodes glareolus, the main reservoir host for Puumala virus [PUUV], which causes HFRS) in Europe. Moreover, we discuss the influence of ecological factors on human hantavirus disease outbreaks and provide an overview of research perspectives. Citation: Tian H, Stenseth NC (2019) The ecological dynamics of hantavirus diseases: From environmental variability to disease prevention largely based on data from China. PLoS Negl Trop Dis 13(2): e0006901. <a href=”https://doi.org/10.1371/journal.pntd.0006901″ rel=”nofollow”>https://doi.org/10.1371/journal.pntd.0006901</a>
Editor: Patricia V. Aguilar, University of Texas Medical Branch, UNITED STATES Published: February 21, 2019 Copyright: © 2019 Tian, Stenseth. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Funding for this study was provided by the Beijing Natural Science Foundation (JQ18025) (http://kw.beijing.gov.cn/jjb/), the National Natural Science Foundation of China (81673234,81460520,31870400,41476161) (http://www.nsfc.gov.cn/), the Young Elite Scientist Sponsorship Program by CAST(YESS)(2018QNRC001) (http://www.cast.org.cn/), the Fundamental Research Funds for the Central Universities (http://www.moe.gov.cn/), the National Key Research and Development Program of China (2016YFA0600104) (http://www.most.gov.cn/), and the health industrys special research funds for public welfare projects (Grant 201502020) (http://www.nhfpc.gov.cn/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. IntroductionHantaviruses are enveloped RNA viruses belonging to the family Hantaviridae, genus Orthohantavirus [1]. They can cause serious diseases in humans, with some outbreaks resulting in case fatality rates of 12% (for hemorrhagic fever with renal syndrome [HFRS] in Europe and Asia) and up to 40% (for hantavirus pulmonary syndrome [HPS] in the Americas), depending on the hantavirus type and the resulting clinical syndrome [2,3]. Hantavirus disease came to global attention when two major outbreaks were reported during the last century. The first, an HFRS outbreak, occurred during the Korean War (1950 to 1953), when more than 3,000 United Nations troops fell ill [4]. The second was an outbreak of HPS that occurred in the Four Corners region of the southwestern United States in 1993 [5]. Hantaviruses remain a global threat to public health; they have been estimated to affect approximately 200,000 humans annually worldwide in recent years [6]. Moreover, the number of countries reporting human cases of hantavirus infection is still on the rise [7]. MethodsSearch strategy and selection criteriaWe searched the MEDLINE (via PubMed) online database and Google Scholar for articles with the key words hantavirus, ecology, or modelling in the title, with no date limit, published before 31 July 2017, with restriction to mainly English papers. Key words used in Medical Subject Headings were hantavirus, hemorrhagic fever with renal syndrome, hantavirus pulmonary syndrome, and rodent reservoir. Inclusion criteria were predefined as research providing information on viral infections (including human incidence, prevalence o ResultsGeographic distributionHantaviruses that cause illness in humans have been identified across the globe [3,7,33] (Fig 1). The major hantavirus disease burden in the Old World is HFRS, and in the New World it is HPS. HTNV in Asia, PUUV and Dobrava virus in Europe, and Seoul virus (SEOV) worldwide are the causative agents of HFRS. SNV, ANDV, and related viruses have been identified as causative agents of HPS in the Americas [3,12]. Recent studies indicate that the medical problem caused by hantavirus infections may be underestimated in Africa, India, Southeast Asia (where Thailand virus [THAIV] has been isolated), and even Europe [25,31,3437] and North America [38,39]. It is estimated that hantavirus diseases are heavily underdiagnosed in Europe; only 20% of PUUV infections have been diagnosed, and no human infections data exist in several countries [31]. Fig 1. Map of Old World and New World hantavirus genotypes reported to be pathogenic for humans. Environment variation and hantavirus reservoir population dynamicsA bottom-up trophic cascade hypothesis has been proposed to explain the chain reactions resulting from climatic conditions, primary productivity, and host demography [27,40,41]. A bottom-up trophic cascade suggests that a change in nutrient supply could lead to similar changes in equilibrium abundances at all trophic levels [42,43]. In rodent host-hantavirus systems, climatic conditions are one of the many factors that can affect rodent population dynamics and, consequently Fig 2. An overview of the ecological dynamics of HFRS caused by HTNV infection. In Central China, an environmentally induced cascading effect on the population dynamics of the striped field mouse (A. agrarius, the main reservoir host for HTNV) was found by combining 30 years of field surveillance and satellite images. The normalized difference vegetation index (NDVI) value for farmland, and precipitation two months previously, were important in determining striped field mouse survival and recruitment rates, respectively [45]. An extreme drought-induced food shortage is thought to increase mortality in striped field mouse populations, as they are a species that relies on farm crops [45]. Furthermore, winter temperature was found to exert complex effects on overwinter survival, thereby affecting the population growth rate in the following year [46]. In South China, the population density of the main reservoir host for SEOV, the brown rat (Rattus norvegicus), is correlated with temperature, precipitation, and the NDVI value for farmland [47]. In northeastern China, in Huludao City, an endemic area for HFRS due to SEOV, climate is considered to affect HFRS epidemics mainly through its effect on the population density of the brown rat (the most abundant rodent species present, accounting for more than 80% of the total rodent population) [48]. In Europe, food-related factors (seed production, climate affecting vegetation biomass) have been linked to rodent populations in deciduous forests [30,49]. Outbreaks of nephropathia epidemica (NE; a mild form of HFRS caused by PUUV infection) are hypothesized to have an ecological causal connection with the staple food source for the main carrier of PUUV, the bank vole, in mast years [32,50,51]. Population densities of bank voles were found to be associated with summer temperature and autumn temperature, both of which favor seed development [52,53]. A higher average winter temperature is believed to reduce winter survival of bank voles in Scandinavia because of a shorter period of protective snow cover against predators. On the contrary, increasing winter temperatures are found to provide a survival benefit to increasing populations of striped field mouse in the spring in Central China; subsequently, a large population of rodents might be accompanied by intraspecific competition due to food or space limitation, resulting in a negative-feedback effect of population density [46]. In North America, the HPS outbreak in 1993 in the Four Corners region of the southwestern US was considered to be driven by increased precipitation induced by an El Niño-Southern Oscillation (ENSO) event. The HPS outbreaks in 1997 in the same region were also preceded by an ENSO event, which brought increased precipitation, favoring deer mouse host populations [26,27]. NDVI is also used to identify locations that can be monitored for the abundance of deer mouse and presence of SNV by examining the seasonal dynamics of vegetative patterns [54]. In central Montana, US, the survival and recruitment rates of the deer mouse were found to be associated with precipitation and temperature, implying a complex relationship between climate and population dynamics [55]. Rodent population dynamics and risk to humansLong-term observations on the prevalence of hantavirus infection in rodent hosts are critical to understanding the dynamics of hantavirus diseases in humans. Similarly, analysis of hostpathogen interactions is important to successfully implement disease control strategies [56]. Hantaviruses are known to be directly transmitted from infected to susceptible hosts (horizontal transmission). Therefore, changes in rodent population densities are expected to increase or decrease the transmission and prevalence of hantavirus infection in rodent reservoir populations, resulting in greater or lower levels of spillover to humans [28]. The dynamics of rodent population density and hantavirus infection prevalence are linked by contact rates; the virus may become extinct below a certain host density, corresponding to the minimum number of hosts required for virus maintenance in a population [57]. A critical population density threshold of striped field mice has been observed in Central China, below which HTNV cannot invade and persist in the population [45]. A similar population density threshold has been observed in the SNV reservoir, the deer mouse, in North America [58,59]. Rodent community composition has also been found to affect the risk of human hantavirus infection among different landscapes [60]. Environmental factors that trigger hantavirus disease outbreaksEnvironmental factors are major triggers that affect reservoir ecology and virus ecology and thus are likely to affect hantavirus transmission from rodent reservoir to humans (or risk of virus exposure in humans). However, although outbreaks appear to be a result of these factors, it is difficult to predict the exact outcome, chiefly due to the complex and multifactorial mechanisms that drive hantavirus disease outbreaks. Studies have highlighted the importance of the interplay between extrinsic and intrinsic factors in determining hantavirus disease dynamics [45,46,74], e.g., when the size of outbreaks is small due to low population susceptibility levels as the result of vaccination or the rodent reservoir population density is below the threshold level required to maintain the virus due to environmental limitations. In this section, studies addressing environmental variability and human hantavirus infections were included (Table 1), and we mainly review three factors that play an important role in altering hantavirus disease dynamics and have been documented sufficientlyprecipitation, temperature, and landscape alteration. Fig 3. Environmental factors associated with hantavirus disease outbreaks. However, precipitation can also negatively affect or have no effect on the incidence of hantavirus disease, depending on magnitude and region [80]. In Europe, no clear relationship of rainfall with human hantavirus infections was shown [77], except that one study illustrated rainfall in the summer three years before hantavirus disease incidence increased [50]. Other studies also demonstrated no significant association between rainfall and hantavirus disease [52,81,82]. In Cascade and Polson, Montana, US, increases in primary productivity, deer mouse population densities, and human disease risk are less sensitive to changes in the amount of rainfall [83]. In low-lying regions of China, such as Anhui Province, HFRS incidence and rodent population density (dominated by the striped field mouse) are all negatively correlated with the total precipitation [8486]. Heavy precipitation there may kill rodents by flooding their burrows and nests, thereby reducing host population density and the risk of human exposure to pathogens. Floods could also cause movement of rodent populations (even community-level changes [87]) to new habitats and eventually disease emergence in new sites. Humananimal interfaceHumananimal interface constitutes the boundary/barrier for cross species transmission of disease and the environment (including ecological and anthropological factors) within which these species exist [92,93]. In the preceding sections, we have summarized the ecological factors and processes that affect hantavirus diseases dynamics; hereafter, anthropological factors will be reviewed, including agricultural activity, human-driven land-use change, and vaccination. In HPS endemic regions of America, agriculture-associated activities were also most commonly reported as potential risk factors [9497], and seropositive rodents were found with high frequency in agricultural landscapes [98,99]. In the HTNV-type endemic area of central China, seasonal pattern of HFRS dynamics is found to coincide with the increase in potential contact between rodents and humans in the dry season due to seasonal agricultural activities [45,100]. Besides, the breeding season of striped field mouse, the local rodent host, is closely associated with agricultural activity. Moreover, it could be concluded that agricultural activity may influence the activity and life cycles of local striped field mouse and in turn shape disease dynamics. Fig 4. Urbanization, immigration, and hantavirus disease epidemics in an endemic area of south China. Vaccination programs against HFRS have been in practice for more than 20 years in China, where the incidence of HFRS has decreased with occasional small fluctuations. It has been reported that the age distribution of HFRS infections has clearly changed in recent years, ever since the Expanded Program of Immunization for regions with high HFRS incidence was implemented in 2008 [115]. Simulations conducted on data from a county in Central China have shown that vaccination will alter the dynamics of HFRS outbreaks [45]. The vaccination-induced reduction in susceptible human population gradually led to the reduction of human hantavirus infections and successfully averted further epidemics. The findings in China therefore highlight the necessity for a vaccination strategy and provide important insights for other countries. DiscussionThe dynamics of hantavirus epidemics involve multiple phases, including environmental drivers that influence infectious diseases, transmission in the animal reservoir, and spillover transmission to humans. The complexity of disease dynamics has been highlighted in recent decades by contradicting trends; the incidence of HFRS has decreased in China [22,116] and increased in Europe [31]. Although pioneering research efforts to study both New World and Old World strains of hantaviruses in rodents have been undertaken, as well as related prevention strategies, it is evident that much work remains to be done. By further studying the transmission dynamics of hantaviruses, better prediction and prevention measures can be implemented to protect human health, and critical insight can be obtained into the ecology of hantaviruses and their rodent hosts. Key Learning PointsWith this review we have demonstrated the following:
Top Five Papers
AcknowledgmentsWe thank Jan Clement and James N. Mills for their valuable comments, which have been very helpful in improving the manuscript. References
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Michael Novakhov – SharedNewsLinks: hantavirus outbreaks after floods – Google Search | ||||
Search ResultsWeb resultsRodent-borne infectious disease outbreaks after flooding …www.ncbi.nlm.nih.gov pubmed
<a href=”http://www.ncbi.nlm.nih.gov” rel=”nofollow”>www.ncbi.nlm.nih.gov</a> pubmed
CONCLUSIONS: Healthcare providers should maintain high levels of suspicion for LS in patients developing febrile illnesses after contaminated freshwater exposures following heavy rainfall, flooding, and even freshwater recreational events; and for Hantavirus-caused infectious diseases in patients with hemorrhagic …
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Rodent-borne Infectious Disease Outbreaks After Flooding …pubmed.ncbi.nlm.nih.gov …
pubmed.ncbi.nlm.nih.gov …
Conclusions: Healthcare providers should maintain high levels of suspicion for LS in patients developing febrile illnesses after contaminated freshwater exposures following heavy rainfall, flooding, and even freshwater recreational events;
and for Hantavirus-caused infectious diseases in patients with hemorrhagic … by JH Diaz – 2015 – Cited by 11 – Related articles
Rodent-borne infectious disease outbreaks after flooding …www.researchgate.net publication 307808285_Rodent…
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Download Citation | Rodent-borne infectious disease outbreaks after flooding … Another zoonotic viral disease after heavy rainfall and flooding is hantavirus …
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Michael Novakhov – SharedNewsLinks: floods and epidemics – Google Search | ||||
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Web resultsFlooding and communicable diseases fact sheet – WHOwww.who.int hac techguidance ems flood_cds
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The lag time is usually around 6-8 weeks before the onset of a malaria epidemic. Malaria epidemics in the wake of flooding are a well-known phenomenon in …
People also search forRelationship between Flooding and Out Break of Infectious …www.ncbi.nlm.nih.gov pmc articles PMC6207902
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New Delhi: After battling the worst flood disaster in Kerala the state is now fearing break out of epidemics …
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Recurrent epidemics and floods following heavy rains in …www.researchgate.net publication 270508689_Recurr…
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Request PDF | Recurrent epidemics and floods following heavy rains in Albertine Region Uganda: A desk review of the vulnerability factors and adaptive …
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Michael Novakhov – SharedNewsLinks: 7:58 AM 7/8/2020 – Merkel looks east as ties fray between Germany and U.S. – POLITICO – Saved, Shared Stories, Tweets
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Merkel looks east as ties fray between Germany and U.S. – POLITICO https://www.politico.com/news/2020/07/07/germany-china-trade-coronavirus-us-351922
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08/07/20 07:40 from TWEETS BY MIKENOV from mikenova (1 sites)
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Covid-19-Review