Imported Malaria Cases Research Articles

A review of malaria molecular markers for drug resistance in Plasmodium falciparum and Plasmodium vivax in China.

China has now achieved the elimination of malaria, but it still faces severe challenges in the post-elimination stage. China continues to be plagued by imported malaria cases, and preventing re-transmission of imported malaria is critical. The effectiveness of antimalarial drugs for malaria control largely depends on the study of drug resistance markers in vitro. Monitoring molecular markers of parasite-associated drug resistance can help predict and manage drug resistance. There is currently a lack of systematic reviews of molecular markers for indigenous and imported malaria in China. Therefore, this review summarizes the published articles related to molecular marker polymorphism of indigenous and imported malaria cases in China in the past two decades, to study the mutation frequency and distribution of crt, mdr1, dhps, dhfr and K13 gene resistance-related loci. This can provide a whole picture of molecular markers and the resistance mutations of imported cases in China, which has certain significance for drug resistance surveillance planning, safe and effective treatment, and preventing the recurrence of local transmission by imported malaria in China in the future.

Mobilizing resources with an investment case to mitigate cross-border malaria transmission and achieve malaria elimination in South Africa

ABSTRACT South Africa’s effort to eliminate malaria is significantly challenged by a large number of imported malaria cases, especially from neighbouring Mozambique. The country has a funding gap to achieve its malaria elimination goals (prior to 2019) and is ineligible to receive a national allocation from the Global Fund. The findings of an IC were utilised to successfully mobilise resources for malaria elimination in South Africa in 2018. A five-step resource mobilisation strategy was implemented to highlight financing challenges and leverage the economic evidence from an IC for malaria elimination in South Africa. South Africa’s malaria programme implements control and elimination activities in three malaria-endemic provinces (KwaZulu Natal, Limpopo, and Mpumalanga). Driven by the IC findings, the South African government took an unprecedented step and increased total domestic malaria financing by approximately 36%, from the 2018/19 to the 2019/20 financial years through the creation of a new conditional grant for malaria. The IC findings predicted that malaria control in southern Mozambique is a prerequisite to eliminate malaria in South Africa. Based on this, the South African government also allocated funding towards a co-financing mechanism to support malaria control efforts in southern Mozambique. The IC findings assisted the South African National Department of Health to make a convincing case to key government decision-makers to invest in national malaria elimination and maximise economic returns in the long run. The South African government is the first in Southern Africa to mobilise a significant increase in domestic malaria financing to address the financial sustainability of both national and regional malaria elimination efforts. Continued surveillance activities will be required to prevent the re-establishment of malaria transmission even after malaria elimination is achieved in South Africa. Information sharing and close collaboration with provincial and national government officials were key to the successful outcome.

Regular assessment is an effective approach to maintaining the capacity of prevention of re-establishment from imported malaria in China

After achieving malaria elimination, preventing re-establishment from imported malaria and consolidating malaria elimination achievements are top priorities of the national malaria control program in China. Due to the long-term existence of overseas imported malaria cases and incomplete eradication of local epidemic conditions, there are multiple challenges for prevention of re-establishment from imported malaria in China. Hereby, we propose that regular assessment is an effective approach to maintaining the capability of prevention of re-establishment from imported malaria, and describe the purpose, significance, management and implementation of the capability assessment for prevention of re-establishment from imported malaria, so as to provide insights into the formulation and adjustment of malaria control strategies during the post-elimination phase.

Imported malaria from land bordering countries in China: A challenge in preventing the reestablishment of malaria transmission

ObjectiveNo indigenous malaria cases have been reported since 2017 in China, but a large number of imported cases are still reported every year, including those from the land bordering countries. To characterize their epidemiological profiles will provide evidence for the development of appropriate strategies to effectively address the challenges of border malaria in the post-elimination phase. MethodsIndividual-level data of imported malaria cases from the land bordering countries were collected from 2017 to 2021 in China via the web-based surveillance systems, and analyzed by SPSS, ArcGIS and WPS software, to explore their epidemiological profiles. ResultsA total of 1170 malaria cases imported into China from six of the fourteen land bordering countries were reported between 2017 and 2021 with a decline trend. Overall, cases were widely distributed in 31–97 counties from 11 to 21 provinces but mainly in Yunnan. Moreover, these imported cases were mainly infected with P. vivax (94.8%), and a total of 68 recurrent cases were reported in 6–14 counties from 4 to 8 provinces. In addition, nearly 57.1% of the total reported cases could seek healthcare within 2 days of getting sick, and 71.3% of the reported cases could be confirmed as malaria on the day they sought medical care. ConclusionsChina still needs to attach great importance to the risk and challenge of the imported malaria from bordering countries particularly from Myanmar in preventing reestablishment of malaria transmission in the post-elimination phase. It is necessary not only to strengthen collaboration and cooperation with the bordering countries, but also coordinate multiple departments at home to improve malaria surveillance and response system and prevent the reestablishment of malaria transmission in China.

Profiling the imported human malaria in Sarawak, Malaysia in 2011-2019.

Malaysia has achieved the status of zero indigenous human malaria cases. Nevertheless, imported human malaria has increasingly been reported in Sarawak, Malaysian Borneo. As zoonotic malaria caused by Plasmodium knowlesi remains a major public health problem in Sarawak, the threat of imported malaria must be addressed as it can cause human malaria reintroduction, sustain transmission, and lead to complications. The objectives of this study were to investigate the epidemiological characteristics of imported malaria cases reported in Sarawak and to underline the challenge posed by imported malaria towards malaria elimination efforts. Imported malaria cases reported in Sarawak from 2011 to 2019 were collected from Sarawak State Health Department and analysed in this longitudinal retrospective study. A total of 2058 imported malaria cases were registered in all districts in Sarawak. Highest number of cases were reported in Kapit (n = 559; 27.16%), followed by Sibu (n = 424; 20.6%), and Miri (n = 166; 8.07%). Based on the demographic profile, most of the patients constituted of either male sex (98.49%), age group of 40-49 years (39.6%), Iban ethnic (57.92%), worked in logging industry (88.58%), Malaysian nationals (91.84%), contracted malaria in Papua New Guinea (46.11%), uncomplicated disease (77.89%), or hospitalised cases (97.86%). The most prominent Plasmodium species diagnosed were P. vivax (52.67%) and P. falciparum (35.81%). Surveillance, disease detection, and medical follow-up must be carried out thoroughly for individuals who returned from malaria-endemic countries. It is also necessary to promote pre-travel preventive education as well as chemoprophylaxis to travellers heading to endemic areas.

The malaria transmission in Anhui province China.

Plasmodium vivax and Plasmodium falciparum cases have opposite trends in Anhui China in the past decade. Long term and seasonal trends in the transmission rate of P. falciparum in Africa has been well studied, however that of P. vivax transmitted by Anopheles sinensis in China has not been investigated. There is a lot of work on the relationship between P. vivax cases and climatic factors in China, with sometimes contradicting results. However, how climatic factors affect transmission rate of P. vivax in China is unknown. We used Anhui province as an example to analyze the recent transmission dynamics where two types of malaria have been reported with differing etiologies. We examined breakpoints of the P. vivax and P. falciparum malaria long term dynamics in the recent decade. For locally transmitted P. vivax malaria, we analyzed the transmission rate and its seasonality using the combined human and mosquitos SIR-SI model with time-varied mosquito biting rate. We identified the effects of meteorological factors on the seasonality in transmission rate using a GAM model. For the imported P. falciparum malaria, we analyzed the potential reason for the observed increase in cases. The breakpoints of P. vivax and P. falciparum dynamics happened in a same year, 2010. The seasonality in the transmission rate of P. vivax malaria was high (42.4%) and was linearly associated with temperature and nonlinearly with rainfall. The abrupt increase in imported P. falciparum cases after the breakpoint was significantly related to the increased annual Chinese investment in Africa. Under the conditions of the existing vectors of malaria, long-term trends in climatic factors, and increasing trend in migration to/from endemic areas and imported malaria cases, we should be cautious of the possibility of the reestablishment of malaria in regions where it has been eliminated or the establishment of other vector-borne diseases.

Malaria in Children: Updates on Management and Prevention.

Malaria in Children: Updates on Management and Prevention.

Questionnaire-Based Analysis of Adverse Events and Compliance with Malaria Chemoprophylaxis in Taiwan

Malaria was eradicated in Taiwan in 1952; however, imported malaria cases are reported every year. The subtropical climate in Taiwan permits mosquito propagation and possible outbreaks of mosquito-borne diseases. The aim of this study was to investigate travelers' compliance and side effects of malaria prophylaxis to prevent a malaria outbreak in Taiwan. In this prospective study, we enrolled travelers who visited our travel clinic before going to malarious areas. A total of 161 questionnaires were collected and analyzed. Associations between the occurrence of side effects and compliance with antimalarial drugs were analyzed. Adjusted odds ratios were calculated after adjusting for potential risk factors in multiple logistic regression analysis. Of the 161 enrolled travelers, 58 (36.0%) reported side effects. Insomnia, somnolence, irritability, nausea, and anorexia were associated with poor compliance. Mefloquine was not associated with more neuropsychological side effects than doxycycline. Multiple logistic regression analysis showed that chemoprophylaxis compliance was affected by a younger age, visiting friends and relatives, visiting the travel clinic more than 1 week before the trip, and preferring to use the same antimalarial regimen on the next trip. Our findings could provide information to travelers besides labeled side effects to improve compliance with malaria prophylaxis and consequently help to prevent malaria outbreaks in Taiwan.

Increasing Trend of Mixed Infections of Plasmodium falciparum and Plasmodium vivax among Imported Malaria Cases in Kuwait, a Non-Endemic Country

Increasing Trend of Mixed Infections of Plasmodium falciparum and Plasmodium vivax among Imported Malaria Cases in Kuwait, a Non-Endemic Country

An Imported Malaria Case Associated With Pregnancy in Northern Cyprus

An Imported Malaria Case Associated With Pregnancy in Northern Cyprus

Impact of Malakit intervention on perceptions, knowledge, attitudes, and practices related to malaria among workers in clandestine gold mines in French Guiana: results of multicentric cross-sectional surveys over time

BackgroundClandestine gold miners remain key hosts for malaria in French Guiana (FG) and contribute to imported malaria cases in Suriname and Brazil. The Malakit intervention, implemented in FG borders with Suriname and Brazil, provided gold miners with training on malaria and kits for self-diagnosis and self-treatment. Having shown a likely impact on malaria transmission, Suriname has now implemented it in routine care for cross-border moving populations. However, a decrease in malaria transmission is frequently associated with a decrease in risk perception, knowledge, and good practices regarding malaria. This study aims to describe the evolution of the perceptions, knowledge, attitudes, and practices (KAP) related to malaria among clandestine gold miners between 2015 and 2019, and to estimate the impact of Malakit on the FG/Suriname border.MethodsThe primary outcome was the overall KAP score over time and among participants and not participants in the Malakit intervention. A propensity score matching analysis and an inverse probability of treatment weighing analysis were used to estimate the Average Treatment effect on the Treated and the Average Treatment Effect of Malakit, respectively.ResultsPerception and knowledge scores were significantly lower in 2019 compared to 2015 (− 0.27 and − 0.23 points, respectively, p < 0.001) while attitude and practice scores were higher (+ 0.16 and + 0.47 points, respectively, p < 0.001). The overall KAP score was significantly higher among participants in Malakit with both propensity score matching (+ 0.72 points, 95%IC [0.29; 1.15]) and inverse probability of treatment weighting analysis (+ 0.70 points, 95%IC [0.34; 1.05]).ConclusionA decrease in perception and knowledge about malaria but an improvement of attitudes and practices as the incidence of malaria decreased are observed. The Malakit intervention seems to have a significant positive impact on the overall KAP related to malaria. The integration of this strategy into malaria control programmes could help to improve the KAP, even in areas where malaria is nearly eliminated, through optimal training and health empowerment.Trial registration ClinicalTrials.gov registration number: NCT03695770.

Profile and determinants of delayed care-seeking and diagnosis among patients with imported malaria: a retrospective study in China, 2014–2021

BackgroundIn areas where malaria has been eliminated, delayed care-seeking and diagnosis of imported malaria are constant threats. This study aimed to describe the profile and determinants of delayed care-seeking and diagnosis among patients with imported malaria in China.MethodsThis retrospective study assessed surveillance data obtained from 2014 to 2021 in the Chinese provincial-level administrative divisions (PLADs) of Anhui, Henan, Hubei, and Zhejiang, and Guangxi. Epidemiological characteristics were analyzed using descriptive statistics. Furthermore, factors associated with delayed care-seeking and diagnosis among imported malaria cases were identified using multivariate logistic regression.ResultsOverall, 11.81% and 30.08% of imported malaria cases had delays in seeking care and diagnosis, respectively. During the study period, there was a decreasing trend in the proportion of imported malaria cases with delayed care-seeking (χ2 = 36.099, P < 0.001) and diagnosis (χ2 = 11.395, P = 0.001). In multivariate analysis, independent risk factors associated with delayed care-seeking include PLADs (Guangxi as reference), consultations in high-level facilities for the first medical visit, infections with non-Plasmodium falciparum species, and older age. However, PLADs (Guangxi as reference), the purpose of traveling (labour as reference), and infections with non-P. falciparum species increased the risk of delayed diagnosis. Delayed care-seeking (adjusted odds ratio: 1.79, P = 0.001) and diagnosis (adjusted odds ratio: 1.62, P = 0.004) were risk factors for severe disease development.ConclusionsBased on this study’s findings, we strongly advocate for improved access to quality healthcare to reduce the rate of misdiagnosis at the first visit. Infections caused by non-P. falciparum species should be highlighted, and more sensitive and specific point-of-care detection methods for non-P. falciparum species should be developed and implemented. In addition, education programs should be enhanced to reach target populations at risk of malaria infection. All these factors may reduce delayed care-seeking and diagnosis of imported malaria.Graphical

Analysis of epidemiological changes and elimination effects for malaria in Handan city, the north China

The elimination of malaria requires high-quality surveillance data to quickly detect and respond to individual cases. This study aims to analyze the epidemiological characteristics of malaria and ascertain the long-term epidemic trends of malaria by 2020 in Handan China. Case-level data for the period 2011 to 2020 were extracted from Chinese Information System for Disease Control and Prevention. The lamp trap method was used to capture mosquitoes so that the characteristics of mosquitoes can be analyzed. The incidence, accuracy, and timeliness of malaria case diagnosis, reporting and investigation were evaluated at the elimination stage (2011-2020) in Handan City, China. Between 2011 and 2020, 94 malaria cases were reported in Handan City, of which 93 malaria cases were male and all of which were imported from abroad. The annual average incidence decreased from 622.33/100,000 to 0.11/100,000 in the elimination stage. Since the initiation of the National Malaria Elimination Program in 2010, malaria cases have been consistent with the increase in overseas export channels and labor personnel service. There is a need to strengthen malaria surveillance of returning workers from Africa and to conduct timely blood tests to diagnose and treat imported infections. Local authorities ensure that imported malaria cases can be timely diagnosed, reported, treated and investigated at local level.

Retrospective spatiotemporal analysis of malaria cases reported between 2000 and 2020 in North Carolina, USA

BackgroundThere are 1,000–2,000 cases of malaria diagnosed in the United States annually and most are imported. MethodsMalaria cases reported between 2000 and 2020 in North Carolina (NC) were analyzed (NC Department of Health and Human Services, Division of Public Health). Differences in numbers of NC malaria cases were further analyzed by year, month, county, gender, age, and country of origin. ResultsMost cases originated from travelers visiting Africa and returning to NC (i.e., Mecklenburg [N = 162 cases], Wake [N = 153], Guilford [N = 103], Durham [N = 74], and Cumberland [N = 41] Counties). Per capita analysis (i.e., per 100,000 population) was used to correct for differences in NC county population sizes and Durham (N = 22.8), Guilford (N = 19.0), Onslow (N = 14.7), Mecklenburg (N = 14.5), Wake (N = 13.5), Orange (N = 12.8) and Cumberland (N = 12.2) Counties showed the highest cases. Malaria was more prevalent among males (N = 532) relative to females (N = 245), and this difference was statistically significant. ConclusionsTravelers visiting malaria-endemic regions should be educated on malaria prevention measures (e.g., chemoprophylaxis, mosquito repellent). These measures should be readily available to travelers. The malaria registry in NC should be improved by requiring additional data related to imported malaria cases.

Application of a low-cost, specific, and sensitive loop-mediated isothermal amplification (LAMP) assay to detect Plasmodium falciparum imported from Africa

BackgroundChinese citizens traveling abroad bring back imported malaria cases to China. Current malaria diagnostic tests, including microscopy and antigen-detecting rapid tests, cannot reliably detect low-density infections. To complement existing diagnostic methods, we aimed to develop a new loop-mediated isothermal amplification (LAMP) assay to detect and identify Plasmodium falciparum in Chinese travelers returning from Africa. MethodsWe developed a miniaturized LAMP assay to amplify the actin I gene of P. falciparum. Each reaction consumed only 25% of the reagents used in a conventional LAMP assay and the same amount of DNA templates used in nested PCR. We evaluated this LAMP assay's performance and compared it to microscopy and a nested PCR assay using 466 suspected malaria cases imported from Africa. We assessed the sensitivity of the new LAMP assay using cultured P. falciparum, clinical samples, and a plasmid construct, allowing unprecedented precision when quantifying the limit of detection. ResultsThe new LAMP assay was highly sensitive and detected two more malaria cases than nested PCR. Compared to nested PCR, the sensitivity and specificity of the novel LAMP assay were 100% [95% confidence interval (CI) 98.5–100%] and 99.1% (95% CI 96.7–99.9%), respectively. When evaluated using serial dilutions of the plasmid construct, the detection limit of the new LAMP was as low as 102 copies/μL, 10-fold lower than PCR. The LAMP assay detected 0.01 parasites/μL of blood (equal to 0.04 parasites/μL of DNA) using cultured P. falciparum and 1–7 parasites/μL of blood (4–28 parasites/μL of DNA) in clinical samples, which is as good as or better than previously reported and commercially licensed assays. ConclusionThe novel LAMP assay based on the P. falciparum actin I gene was specific, sensitive, and cost-effective, as it consumes 1/4 of the reagents in a typical LAMP reaction.

Imported malaria definition and minimum data for surveillance

The mobility of malaria-infected individuals poses challenges to elimination campaigns by way of spreading parasite drug resistance, straining country-to-country collaboration, and making routine data collection difficult, especially in resource-poor settings. Nevertheless, no concerted effort has been made to develop a common framework to define the spatial and temporal components of an imported malaria case and recommend the minimum data needed to identify it. We conducted a scoping review of imported malaria literature from 2010 to 2020 which showed that definitions vary widely, and local capabilities of detecting importation are often restricted in low-income countries. Following this, we propose a common definition for imported malaria and the minimum data required to identify a case, depending on the country’s capability of conducting an epidemiological investigation. Lastly, we utilize the proposed definition using data from Brazil to demonstrate both the feasibility and the importance of tracking imported cases. The case of Brazil highlights the capabilities of regular surveillance systems to monitor importation, but also the need to regularly use these data for informing local responses. Supporting countries to use regularly collected data and adopt a common definition is paramount to tackling the importation of malaria cases and achieving elimination goals set forth by the World Health Organization.

Comparative Assessment of the Sensitivity of Ten Commercial Rapid Diagnostic Test Kits for the Detection of Plasmodium.

Malaria is one of the most common tropical diseases encountered by members of the French military who are deployed in operations under constrained conditions in malaria-endemic areas. Blood smear microscopy—the gold standard for malaria diagnosis—is often not available in such settings, where the detection of malaria relies on rapid diagnostic tests (RDTs). Ten RDTs (from Biosynex, Carestart, Humasis, SD Bioline, and CTK Biotech), based on the detection of the Plasmodium falciparum histidine-rich protein 2 (HRP2) or lactate dehydrogenase (pLDH, PfLDH, or PvLDH), were assessed against 159 samples collected from imported malaria cases, including 79 P. falciparum, 37 P. vivax, 22 P. ovale, and 21 P. malariae parasites. Samples had been previously characterised using microscopy and real-time PCR. The overall sensitivities for the Plasmodium test ranged from 69.8% (111/159) to 95% (151/159). There was no significant difference for the specific detection of P. falciparum (96.2% to 98.7%, p = 0.845). No significant difference was found between sensitivities to P. vivax by pan LDH or pvLDH (81.1% (30/37) to 94.6% (35/37) (p = 0.845)). Some of the RDTs missed most of P. ovale and P. malariae, with sensitivities for all RDTs ranging respectively from 4.5% (1/22) to 81.8% (18/22) and 14.3% (3/21) to 95.2% (20/21). Carestart Malaria Pf/Pan (pLDH) Ag G0121, a pLDH-based RDT (PfLDH and pLDH), showed the highest sensitivities to P. falciparum (98.7%, 78/79), P. vivax (94.6%, 35/37), P. ovale (81.8%, 18/22), and P. malariae (95.2%, 20/21) and meets the requirements for military deployments in malaria-endemic areas.

Epidemiology and clinical features of imported malaria: a 14-year retrospective single-centre descriptive study in Prague, Czech Republic

BackgroundMalaria represents one of the most important imported tropical infectious diseases in European travellers. The objective of the study was to identify changes in the epidemiological features of imported malaria and to analyse the clinical findings and outcomes of imported malaria.MethodsThis single-centre descriptive study retrospectively analysed the medical records of all imported malaria cases in travellers treated at the Department of Infectious Diseases of University Hospital Bulovka in Prague from 2006 to 2019.ResultsThe study included 203 patients with a median age of 37 years (IQR 30–48) and a male to female ratio of 3.72:1. Plasmodium falciparum was the predominant species (149/203), and its proportion significantly increased from 35/60 cases (58.3%) in 2006–2011 to 69/80 (86.3%) in 2016–2019 (p < 0.001). In contrast, the incidence of Plasmodium vivax malaria decreased from 19/60 cases (31.7%) in 2006–2011 to 5/80 (6.3%) in 2016–2019 (p < 0.001). Malaria was imported from sub-Saharan Africa in 161/203 cases (79.3%). The proportion of travellers from Southeast and South Asia decreased from 16/60 (26.7%) and 6/60 (10.0%) in 2006–2011 to 2/80 (2.5%) and no cases (0.0%) in 2016–2019, respectively (p < 0.001 and p = 0.006). Tourism was the most common reason for travel (82/203), however, the proportion of non-tourists significantly increased over time from 29/60 (48.3%) in 2006–2011 to 55/80 (68.8%) in 2016–2019, p = 0.015. Severe malaria developed in 32/203 (15.8%) patients who were significantly older (p = 0.013) and whose treatment was delayed (p < 0.001). Two lethal outcomes were observed during the study period.ConclusionsThis study demonstrated a significant increase in P. falciparum malaria, which frequently resulted in severe disease, especially in older patients and those with delayed treatment initiation. The rising proportion of imported malaria in non-tourists, including business travellers and those visiting friends and relatives, is another characteristic finding analogous to the trends observed in Western European and North American centres. The described changes in the aetiology and epidemiology of imported malaria may serve to optimize pre-travel consultation practices and improve post-travel diagnostics and medical care.

An epidemiological analysis of imported malaria in Shanghai during a COVID-19 outbreak

BackgroundThe goal of this study was to understand the epidemiological characteristics of imported malaria in Shanghai specifically during the epidemic period of novel corona-virus pneumonia (COVID-19), to provide a reference for preventing the transmission of imported malaria after this disease had been previously eliminated.MethodsThe data of malaria cases reported in Shanghai from 2020 to 2021 were obtained from the China Information System for Disease Control and Prevention (CISDCP) and the Information System for Parasitic Disease Control and Prevention (ISPDCP). The characteristics of demographic and epidemiological distribution, travel-related information, diagnosis information, regions of infection acquisition and disposal information of epidemic situation were analysed with descriptive statistics.ResultsA total of 112 cases of malaria were reported in Shanghai from January 2020 to December 2021. There were 18 cases and 94 cases in 2020 and 2021, respectively, reaching the lowest and highest levels in the past 10 years. The incidence of malaria associated with seasons had an increasing trend (χ2 = 81.143, P < 0.05). These cases included Plasmodium falciparum (97, 86.61%), Plasmodium vivax (4, 3.57%), Plasmodium ovale (8, 7.14%) and Plasmodium malariae (3, 2.68%). The median age of patients with malaria was 38.0 years, the majority of these individuals were males (109, 97.32%), and most of them were labour personnel (93, 83.04%). Of the reported cases, 8 of these individuals (7.14%) reported experiencing malaria symptoms before their arrival in China after their stay overseas; 97 of these individuals (86.61%) reported experiencing symptoms within 14 days after their initial arrival from overseas; 15 of these individuals (13.39%) were diagnosed with ‘severe malaria’; and 4 of these individuals (3.57%) were also diagnosed with COVID-19. All cases were imported from Africa, and there were no indigenous cases and deaths.ConclusionDue to the impact of COVID-19, the number of imported malaria cases in Shanghai had greatly increased; however, prevention and control measures for imported malaria could be implemented to prevent re-transmission of this condition. Considering that the number of individuals returning from overseas labour is likely to increase in the next few years, it is necessary to strengthen the surveillance of imported malaria and to review the protocol for potential epidemic situations. Together, these measures could support the maintation of free-malaria status in Shanghai.

Impact of Chemoprophylaxis on Plasmodium vivax and Plasmodium ovale Infection Among Civilian Travelers: A Nested Case-Control Study With a Counterfactual Approach on 862 Patients.

The impact of chemoprophylaxis targeting Plasmodium falciparum on Plasmodium vivax and Plasmodium ovale, which may remain quiescent as hypnozoites in the liver, is debated. We conducted a nested case-control analysis of the outcomes of P. vivax and P. ovale infections in imported malaria cases in France among civilian travelers from 1 January 2006, to 31 December 2017. Using adjusted logistic regression, we assessed the effect of chemoprophylaxis on the incubation period, time from symptoms to diagnosis, management, blood results, symptoms, and hospitalization duration. We analyzed the effect of blood-stage drugs (doxycycline, mefloquine, chloroquine, chloroquine-proguanil) or atovaquone-proguanil on the incubation period. We used a counterfactual approach to ascertain the causal effect of chemoprophylaxis on postinfection characteristics. Among 247 P. vivax- and 615 P. ovale-infected travelers, 30% and 47%, respectively, used chemoprophylaxis, and 7 (3%) and 8 (1%) were severe cases. Chemoprophylaxis users had a greater risk of presenting symptoms >2 months after returning for both species (P. vivax odds ratio [OR], 2.91 [95% confidence interval {CI}, 1.22-6.95], P = .02; P. ovale OR, 2.28 [95% CI, 1.47-3.53], P < .001). Using drugs only acting on the blood stage was associated with delayed symptom onset after 60 days, while using atovaquone-proguanil was not. Civilian travelers infected with P. vivax or P. ovale reporting chemoprophylaxis use, especially of blood-stage agents, had a greater risk of delayed onset of illness. The impact of chemoprophylaxis on the outcomes of infection with relapse-causing species calls for new chemoprophylaxis acting against erythrocytic and liver stages.