Dear editor,Mosquito-borne diseases,viz.,malaria,filariasis,dengue hemorrhagic fever,chikungunya,Japanese encephalitis etc.,created huge impact on humans over the world,and the chemical insecticides remain the mainsta...Dear editor,Mosquito-borne diseases,viz.,malaria,filariasis,dengue hemorrhagic fever,chikungunya,Japanese encephalitis etc.,created huge impact on humans over the world,and the chemical insecticides remain the mainstay of effective control.But,indiscriminate and rampant use of the chemical insecticides in controlling mosquito vectors,in order to prevent diseases vectored by them,has resulted problems related to the adverse environmental effects for their(insecticides)potential toxicity,high operational cost,community acceptance,and the development of insecticide resistance among the vectors.The factors mentioned above prompted the search for new means of control strategies.Currently,the botanicals(viz.,plant extracts,essential oils and phytochemicals)with mosquitocidal potential展开更多
Most of the vector-borne diseases show a clear dependence on seasonal variation,including climate change.In this paper,we proposed a nonautonomous mathematical model consisting of a periodic system of nonlinear differ...Most of the vector-borne diseases show a clear dependence on seasonal variation,including climate change.In this paper,we proposed a nonautonomous mathematical model consisting of a periodic system of nonlinear differential equations.In the proposed model,the realistic functional forms for the different temperature-dependent parameters are considered.The autonomous system of the proposed model is also analyzed.The nontrivial solution of the autonomous model is locally asymptotically stable if R0<1.It is shown that a unique endemic equilibrium point of the autonomous model exists when R0>1 and proved that endemic solution is linearly stable when R0>1.The nonautonomous model is shown to have a nontrivial disease-free periodic state,which is globally asymptotically stable whenever temperature-dependent reproduction number is less than unity.It is observed that a unique positive endemic periodic solution of the nonautonomous system exists only when a temperature-dependent reproduction number greater than unity,which makes for the persistence of the disease.Numerical simulation has been carried out to support the analytical results and shows the effects of temperature variability in the life span of mosquitoes as well as the persistence of the disease.展开更多
Background:Mosquito-based arbovirus surveillance can serve as an early warning in evaluating the status of mosquito-borne virus prevalence and thus prevent local outbreaks.Although Tengchong County in Yunnan Province-...Background:Mosquito-based arbovirus surveillance can serve as an early warning in evaluating the status of mosquito-borne virus prevalence and thus prevent local outbreaks.Although Tengchong County in Yunnan Province-which borders Myanmar-is abundant and diverse in mosquitoes,very few mosquito-based arbovirus investigations have been conducted in the recent decade.Herein,this study aims to evaluate the presence and the diffusion of mosquito-borne pathogens,currently prevalent in this region.展开更多
BACKGROUND:The Chikungunya(CHIK)virus was recently reported by the CDC to have spread to the United States.We report an early documented case of CHIK from the state of Pennsylvania after a patient recently returned fr...BACKGROUND:The Chikungunya(CHIK)virus was recently reported by the CDC to have spread to the United States.We report an early documented case of CHIK from the state of Pennsylvania after a patient recently returned from Haiti in June of 2014.METHODS:A 39-year-old man presented to the emergency department complaining of fever,fatigue,polyarthralgias and a diffuse rash for two days.Four days before,he returned from a mission trip to Haiti and reported that four of his accompanying friends had also become ill.A CHIK antibody titer was obtained and it was found to be positive.During his hospital stay,he responded well to supportive care,including anti-inflammatories,intravenous hydration and anti-emetics.RESULTS:His condition improved within two days and he was ultimately discharged home.CONCLUSIONS:Manifestations of CHIK can be similar to Dengue fever,which is transmitted by the same species of mosquito,and occasionally as a co-infection.Clinicians should include Chikungunya virus in their differential diagnosis of patients who present with fever,polyarthralgia and rash with a recent history of travel to endemic areas,including those within the United States.展开更多
The amount and distribution of precipitation can determine dengue risk by affecting mosquito breeding;however,previous studies failed to incorporate this bivariate characteristic to examine dengue fever transmission.I...The amount and distribution of precipitation can determine dengue risk by affecting mosquito breeding;however,previous studies failed to incorporate this bivariate characteristic to examine dengue fever transmission.In the present research,nationwide data on daily dengue cases in China between January 2005 and December 2020 were obtained,and the top 12 cities accounting for 78%of total cases were selected for analysis.Precipitation patterns were quantified by weekly precipitation and precipitation concentration degree(PCD).On the basis of the combinations of both parameters,the exposure-response relationships of precipitation with dengue risk were established using generalised additive models,and the high-dengue-risk thresholds of precipitation patterns were further identified.Dengue burden was assessed by calculating attributable dengue cases.For the same amount of precipitation,the dispersed precipitation in the pre-summer rainy season leads to a higher dengue risk in autumn.The weekly precipitation of 100-150 mm and PCD of 0.2-0.4 constitute the highest risk scenario,and the average frequency of precipitation associated with dengue risk in 2013-2020 is 1.6 times higher than that in 2005-2012.A total of 3093 attributable dengue cases are identified.From 2005 to 2020,the amount of dispersed precipitation increased in southern and southwestern China and posed high dengue risks in central China.This study has improved the understanding of the health impacts of irregular rainfall under climate change.Our approach to identifying thresholds provides information for early warning systems and helps reduce the risk of dengue transmission in the long run.展开更多
In this paper,a delayed mosquito population suppression model,where the number of sexually active sterile mosquitoes released is regarded as a given nonnegative function,and the birth process is density dependent by c...In this paper,a delayed mosquito population suppression model,where the number of sexually active sterile mosquitoes released is regarded as a given nonnegative function,and the birth process is density dependent by considering larvae progression and the intra-specific competition within the larvae,is developed and studied.A threshold value r^(*)for the releases of sterile mosquitoes is determined,and it is proved that the origin is globally asymptotically stable if the number of sterile mosquitoes released is above the threshold value r^(*).Besides,the case when the number of sterile mosquitoes released stays at a constant level r is also considered.In the special case,it is also proved that the origin is globally asymptotically stable if and only if r>r^(*)and that the model exhibits other complicated dynamics such as bi-stability and semi-stability when r≤r^(*).Numerical examples are also provided to illustrate our main theoretical results.展开更多
Introduction:Yellow fever(YF)is primarily transmitted by Haemagogus species of mosquitoes.Under climate change,mosquitoes and the pathogens that they carry are expected to develop faster,potentially impacting the case...Introduction:Yellow fever(YF)is primarily transmitted by Haemagogus species of mosquitoes.Under climate change,mosquitoes and the pathogens that they carry are expected to develop faster,potentially impacting the case count and duration of YF outbreaks.The aim of this study was to determine how YF virus outbreaks in Brazil may change under future climate,using ensemble simulations from regional climate models under RCP4.5 and RCP8.5 scenarios for three time periods:2011-2040(short-term),2041-2070(mid-term),and 2071-2100(long-term).Methods:A compartmental model was developed to fit the 2017/18 YF outbreak data in Brazil using least squares optimization.To explore the impact of climate change,temperature-sensitive mosquito parameters were set to change over projected time periods using polynomial equations fitted to their relationship with temperature according to the average temperature for years 2011-2040,2041-2070,and 2071-2100 for climate change scenarios using RCP4.5 and RCP8.5,where RCP4.5/RCP8.5 corresponds to intermediate/high radiative forcing values and to moderate/higher warming trends.A sensitivity analysis was conducted to determine how the temperature-sensitive parameters impacted model results,and to determine how vaccination could play a role in reducing YF in Brazil.Results:Yellow fever case projections for Brazil from the models varied when climate change scenarios were applied,including the peak clinical case incidence,cumulative clinical case incidence,time to peak incidence,and the outbreak duration.Overall,a decrease in YF cases and outbreak duration was observed.Comparing the observed incidence in 2017/18 to the projected incidence in 2070-2100,for RCP4.5,the cumulative case incidence decreased from 184 to 161,and the outbreak duration decreased from 21 to 20 weeks.For RCP8.5,the peak case incidence decreased from 184 to 147,and the outbreak duration decreased from 21 to 17 weeks.The observed decrease was primarily due to temperature increasing beyond that suitable for Haemagogus mosquito survival.Conclusions:Climate change is anticipated to have an impact on mosquito-borne diseases.We found outbreaks of YF may reduce in intensity as temperatures increase in Brazil;however,temperature is not the only factor involved with disease transmission.Other factors must be explored to determine the attributable impact of climate change on mosquito-borne diseases.展开更多
文摘Dear editor,Mosquito-borne diseases,viz.,malaria,filariasis,dengue hemorrhagic fever,chikungunya,Japanese encephalitis etc.,created huge impact on humans over the world,and the chemical insecticides remain the mainstay of effective control.But,indiscriminate and rampant use of the chemical insecticides in controlling mosquito vectors,in order to prevent diseases vectored by them,has resulted problems related to the adverse environmental effects for their(insecticides)potential toxicity,high operational cost,community acceptance,and the development of insecticide resistance among the vectors.The factors mentioned above prompted the search for new means of control strategies.Currently,the botanicals(viz.,plant extracts,essential oils and phytochemicals)with mosquitocidal potential
文摘Most of the vector-borne diseases show a clear dependence on seasonal variation,including climate change.In this paper,we proposed a nonautonomous mathematical model consisting of a periodic system of nonlinear differential equations.In the proposed model,the realistic functional forms for the different temperature-dependent parameters are considered.The autonomous system of the proposed model is also analyzed.The nontrivial solution of the autonomous model is locally asymptotically stable if R0<1.It is shown that a unique endemic equilibrium point of the autonomous model exists when R0>1 and proved that endemic solution is linearly stable when R0>1.The nonautonomous model is shown to have a nontrivial disease-free periodic state,which is globally asymptotically stable whenever temperature-dependent reproduction number is less than unity.It is observed that a unique positive endemic periodic solution of the nonautonomous system exists only when a temperature-dependent reproduction number greater than unity,which makes for the persistence of the disease.Numerical simulation has been carried out to support the analytical results and shows the effects of temperature variability in the life span of mosquitoes as well as the persistence of the disease.
文摘Background:Mosquito-based arbovirus surveillance can serve as an early warning in evaluating the status of mosquito-borne virus prevalence and thus prevent local outbreaks.Although Tengchong County in Yunnan Province-which borders Myanmar-is abundant and diverse in mosquitoes,very few mosquito-based arbovirus investigations have been conducted in the recent decade.Herein,this study aims to evaluate the presence and the diffusion of mosquito-borne pathogens,currently prevalent in this region.
文摘BACKGROUND:The Chikungunya(CHIK)virus was recently reported by the CDC to have spread to the United States.We report an early documented case of CHIK from the state of Pennsylvania after a patient recently returned from Haiti in June of 2014.METHODS:A 39-year-old man presented to the emergency department complaining of fever,fatigue,polyarthralgias and a diffuse rash for two days.Four days before,he returned from a mission trip to Haiti and reported that four of his accompanying friends had also become ill.A CHIK antibody titer was obtained and it was found to be positive.During his hospital stay,he responded well to supportive care,including anti-inflammatories,intravenous hydration and anti-emetics.RESULTS:His condition improved within two days and he was ultimately discharged home.CONCLUSIONS:Manifestations of CHIK can be similar to Dengue fever,which is transmitted by the same species of mosquito,and occasionally as a co-infection.Clinicians should include Chikungunya virus in their differential diagnosis of patients who present with fever,polyarthralgia and rash with a recent history of travel to endemic areas,including those within the United States.
基金supported by the National Key R&D Program of China(2018YFA0606200)the Sanming Project of Medicine in Shenzhen,China(SZSM202111001).
文摘The amount and distribution of precipitation can determine dengue risk by affecting mosquito breeding;however,previous studies failed to incorporate this bivariate characteristic to examine dengue fever transmission.In the present research,nationwide data on daily dengue cases in China between January 2005 and December 2020 were obtained,and the top 12 cities accounting for 78%of total cases were selected for analysis.Precipitation patterns were quantified by weekly precipitation and precipitation concentration degree(PCD).On the basis of the combinations of both parameters,the exposure-response relationships of precipitation with dengue risk were established using generalised additive models,and the high-dengue-risk thresholds of precipitation patterns were further identified.Dengue burden was assessed by calculating attributable dengue cases.For the same amount of precipitation,the dispersed precipitation in the pre-summer rainy season leads to a higher dengue risk in autumn.The weekly precipitation of 100-150 mm and PCD of 0.2-0.4 constitute the highest risk scenario,and the average frequency of precipitation associated with dengue risk in 2013-2020 is 1.6 times higher than that in 2005-2012.A total of 3093 attributable dengue cases are identified.From 2005 to 2020,the amount of dispersed precipitation increased in southern and southwestern China and posed high dengue risks in central China.This study has improved the understanding of the health impacts of irregular rainfall under climate change.Our approach to identifying thresholds provides information for early warning systems and helps reduce the risk of dengue transmission in the long run.
基金supported by the National Natural Science Foundation of China (No.12171193)the Science and Technology Key Project of Henan Province of China (No.222102110028)the Key scientific research projects of colleges and universities in Henan Province of China (Nos.22B110006,22A110012 and 20B110008).
文摘In this paper,a delayed mosquito population suppression model,where the number of sexually active sterile mosquitoes released is regarded as a given nonnegative function,and the birth process is density dependent by considering larvae progression and the intra-specific competition within the larvae,is developed and studied.A threshold value r^(*)for the releases of sterile mosquitoes is determined,and it is proved that the origin is globally asymptotically stable if the number of sterile mosquitoes released is above the threshold value r^(*).Besides,the case when the number of sterile mosquitoes released stays at a constant level r is also considered.In the special case,it is also proved that the origin is globally asymptotically stable if and only if r>r^(*)and that the model exhibits other complicated dynamics such as bi-stability and semi-stability when r≤r^(*).Numerical examples are also provided to illustrate our main theoretical results.
文摘Introduction:Yellow fever(YF)is primarily transmitted by Haemagogus species of mosquitoes.Under climate change,mosquitoes and the pathogens that they carry are expected to develop faster,potentially impacting the case count and duration of YF outbreaks.The aim of this study was to determine how YF virus outbreaks in Brazil may change under future climate,using ensemble simulations from regional climate models under RCP4.5 and RCP8.5 scenarios for three time periods:2011-2040(short-term),2041-2070(mid-term),and 2071-2100(long-term).Methods:A compartmental model was developed to fit the 2017/18 YF outbreak data in Brazil using least squares optimization.To explore the impact of climate change,temperature-sensitive mosquito parameters were set to change over projected time periods using polynomial equations fitted to their relationship with temperature according to the average temperature for years 2011-2040,2041-2070,and 2071-2100 for climate change scenarios using RCP4.5 and RCP8.5,where RCP4.5/RCP8.5 corresponds to intermediate/high radiative forcing values and to moderate/higher warming trends.A sensitivity analysis was conducted to determine how the temperature-sensitive parameters impacted model results,and to determine how vaccination could play a role in reducing YF in Brazil.Results:Yellow fever case projections for Brazil from the models varied when climate change scenarios were applied,including the peak clinical case incidence,cumulative clinical case incidence,time to peak incidence,and the outbreak duration.Overall,a decrease in YF cases and outbreak duration was observed.Comparing the observed incidence in 2017/18 to the projected incidence in 2070-2100,for RCP4.5,the cumulative case incidence decreased from 184 to 161,and the outbreak duration decreased from 21 to 20 weeks.For RCP8.5,the peak case incidence decreased from 184 to 147,and the outbreak duration decreased from 21 to 17 weeks.The observed decrease was primarily due to temperature increasing beyond that suitable for Haemagogus mosquito survival.Conclusions:Climate change is anticipated to have an impact on mosquito-borne diseases.We found outbreaks of YF may reduce in intensity as temperatures increase in Brazil;however,temperature is not the only factor involved with disease transmission.Other factors must be explored to determine the attributable impact of climate change on mosquito-borne diseases.
