We are pleased to introduce the collection Frontiers in Tropical Diseases – Highlights in Emerging Tropical Diseases 2021/22. This collection will welcome and showcase a selection of high impact articles authored by leaders in the field. The work presented here highlights the broad diversity of research performed across the Emerging Tropical Diseases section, and aims to put a spotlight on the main areas of interest. This collection aims to further support Frontiers’ strong community by shining a spotlight on our authors' highly impactful research.

Simón Bolívar University

University of Quindío

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Frontiers in Tropical Diseases

Emerging Tropical Diseases

Highlights in Emerging Tropical Diseases 2021/22

The articles in this Research Topic, “Highlights in Emerging Tropical Diseases 2021/22”, are a demonstration of the central place that the control of infections in tropical settings has during the current global climate change situation (<a href="#B1">1</a>). The last report from the Intergovernmental Panel on Climate Change (IPCC) group confirms with high confidence that climate change will increase the number of deaths and the global burden of non-communicable and infectious diseases (<a href="#B2">2</a>). The increase in temperature (global warming) is one of the variables with the greatest impact on climate change and is responsible for the increase in vector-borne diseases (<a href="#B3">3</a>). The call for specific action from the specialists that inaugurated the new journal, Frontiers in Tropical Diseases, is presented in the first article of the present Research Topic and is a perfect summary of the current status of the challenges presented by emerging infectious diseases in tropical regions (<a href="https://doi.org/10.3389/fitd.2021.676905">Rodriguez-Morales et&nbsp;al.</a>). Certainly, the increasing urgencies due to climate change are being presented faster than anticipated (<a href="#B2">2</a>) and will need energetic concerted action (<a href="#B4">4</a>).The article by <a href="https://doi.org/10.3389/fitd.2021.707865">Salcedo et&nbsp;al.</a> is a good example of how ingenious modifications of diagnostic technologies can contribute to reducing costs in poorly resourced countries. The urgency occasioned by the COVID-19 pandemic for public health organizations and health ministries around the world pushed researchers to look for alternatives given the scarcity of diagnostic reagents (<a href="#B5">5</a>), bringing great impact in low and middle-income countries.Finally, the article by Nunes et&nbsp;al. describes the epidemiological and ecological determinants for spotted fever in Minas Gerais state in Brazil and contributes crucial information for this largely unexplored cause of febrile diseases. The situation revealed by this study provides lines of action for public health measures, including active surveillance and control for vectors of this disease. Multiple emerging and reemerging tropical diseases, particularly those that are zoonotic and vector-borne, will continue to cause multiple public health threats (<a href="https://doi.org/10.3389/fitd.2021.676905">Rodriguez-Morales et&nbsp;al.</a>).In summary, this Research Topic provides a frame of analysis for critical issues in emerging tropical infectious diseases, one of the most important current global challenges. One should always take into account that to carry out a good intervention in these tropical diseases, an integral approach must be followed, encompassing the environment, etiological agent, and host, which is the strategy of One Health (<a href="#B6">6</a>). All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.The authors JG-M, WV-G, and AR-M declared that they were editorial board members of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Editorial: Highlights in emerging tropical diseases 2021/22

West Nile virus (WNV) is a zoonotic, emerging mosquito-borne virus which can cause severe disease in the form of encephalitis and acute flaccid paralysis in humans. In Assam, northeast India, arboviruses seem to be re-emerging, however, WNV has been little studied. The present investigation was carried out from April, 2018 to March, 2019 to study sero-positivity of WNV in chicken in urban and peri-urban areas of Guwahati, the capital city of Assam. Four urban and four peri-urban areas of Guwahati were selected. A total of 864 chicken serum samples (72 samples per month) were screened by ELISA and further confirmed by haemagglutination inhibition (HI), which revealed that 3.13% of the chickens had been exposed to WNV, with 0.69% sero-positivity in urban areas compared to 5.56% in peri-urban. Peak sero-prevalence of WNV were reported during the month of July and August with 8.33% each with lowest sero-prevalence being recorded in November (1.39%) and no sero-positive birds from December to April. These results indicate that WNV is one of the actively circulating flaviviruses in Assam, and human febrile and encephalitic cases should be screened for the disease.

West Nile virus (WNV) is a zoonotic, emerging mosquito-borne virus which can cause severe disease in the form of encephalitis and acute flaccid paralysis in humans. In Assam, northeast India, arboviruses seem to be re-emerging, however, WNV has been little studied. The present investigation was carried out from April, 2018 to March, 2019 to study sero-positivity of WNV in chicken in urban and peri-urban areas of Guwahati, the capital city of Assam. Four urban and four peri-urban areas of Guwahati were selected. A total of 864 chicken serum samples (72 samples per month) were screened by ELISA and further confirmed by haemagglutination inhibition (HI), which revealed that 3.13% of the chickens had been exposed to WNV, with 0.69% sero-positivity in urban areas compared to 5.56% in peri-urban. Peak sero-prevalence of WNV were reported during the month of July and August with 8.33% each with lowest sero-prevalence being recorded in November (1.39%) and no sero-positive birds from December to April. These results indicate that WNV is one of the actively circulating flaviviruses in Assam, and human febrile and encephalitic cases should be screened for the disease.

Sero-Prevalence of West Nile Virus in Urban and Peri-Urban Poultry Farms of Guwahati, India

In Brazil, the tick-borne rickettsiosis known as Spotted Fever (SF) has been recorded from 59% of the Federative Units, however, the knowledge of the epidemiology and dynamics of human infection remains incipient in certain areas, complicating appropriate public health actions to inform the general population and control the disease. Here, we improved the interpretation of epidemiological information of SF cases recorded for an important endemic area. A descriptive epidemiological study was carried out based on records in the SINAN (Notifiable Diseases Information System) SF case databases. Data analysis was performed using Python programming language, Pandas library and Qgis map making. To evaluate the sociodemographic, clinical, assistance, laboratory and epidemiological characteristics, simple and relative nominal values of occurrences, means and standard deviations, and molecular analyzes were performed to identify the bioagent present in biological samples collected during each case investigation. Of the 298 confirmed cases, 98 resulted in death, the number of cases increased from 2011, and the disease scenario had 32.8% lethality. Overall, 207 cases involved men, and lethality was higher in this group. The most affected age group was 30 to 59 years old. The majority of patients reported having had contact with animals such as ticks, capybara and domestic animals such as dogs and cats. The results corroborate existing studies in areas of severe SF cases in Brazil. Despite reports of SF cases from the Cerrado Biome, analyses show that serious cases occur in anthropized areas of the Atlantic Forest biome, and in a transition area between this and the Cerrado. Complex, longitudinal, multidisciplinary studies, with an eco-epidemiological focus, should be carried out to allow the construction of algorithms capable of predicting, in time and space, the risk factors associated with severe cases and deaths from SF, with the aim of avoiding their expansion.

In Brazil, the tick-borne rickettsiosis known as Spotted Fever (SF) has been recorded from 59% of the Federative Units, however, the knowledge of the epidemiology and dynamics of human infection remains incipient in certain areas, complicating appropriate public health actions to inform the general population and control the disease. Here, we improved the interpretation of epidemiological information of SF cases recorded for an important endemic area. A descriptive epidemiological study was carried out based on records in the SINAN (Notifiable Diseases Information System) SF case databases. Data analysis was performed using Python programming language, Pandas library and Qgis map making. To evaluate the sociodemographic, clinical, assistance, laboratory and epidemiological characteristics, simple and relative nominal values of occurrences, means and standard deviations, and molecular analyzes were performed to identify the bioagent present in biological samples collected during each case investigation. Of the 298 confirmed cases, 98 resulted in death, the number of cases increased from 2011, and the disease scenario had 32.8% lethality. Overall, 207 cases involved men, and lethality was higher in this group. The most affected age group was 30 to 59 years old. The majority of patients reported having had contact with animals such as ticks, capybara and domestic animals such as dogs and cats. The results corroborate existing studies in areas of severe SF cases in Brazil. Despite reports of SF cases from the Cerrado Biome, analyses show that serious cases occur in anthropized areas of the Atlantic Forest biome, and in a transition area between this and the Cerrado. Complex, longitudinal, multidisciplinary studies, with an eco-epidemiological focus, should be carried out to allow the construction of algorithms capable of predicting, in time and space, the risk factors associated with severe cases and deaths from SF, with the aim of avoiding their expansion.

Spotted Fever in the Morphoclimatic Domains of Minas Gerais State, Brazil

While molecular assays, such as reverse-transcription polymerase chain reaction (RT-PCR), have been widely used throughout the coronavirus disease 2019 (COVID-19) pandemic, the technique is costly and resource intensive. As a means to reduce costs and increase diagnostic efficiency, pooled testing using RT-PCR has been implemented. However, pooling samples for antigen testing has not been evaluated. Here, we propose a proof-of-concept pooling strategy for antigen testing that would significantly expand SARS-CoV-2 surveillance, especially for low-to-middle income countries, schools, and workplaces. Our laboratory-based testing demonstrates that combining of up to 20 nasal swab specimens per pool can expand surveillance with antigen tests, even if a pool contains only one positive sample.

While molecular assays, such as reverse-transcription polymerase chain reaction (RT-PCR), have been widely used throughout the coronavirus disease 2019 (COVID-19) pandemic, the technique is costly and resource intensive. As a means to reduce costs and increase diagnostic efficiency, pooled testing using RT-PCR has been implemented. However, pooling samples for antigen testing has not been evaluated. Here, we propose a proof-of-concept pooling strategy for antigen testing that would significantly expand SARS-CoV-2 surveillance, especially for low-to-middle income countries, schools, and workplaces. Our laboratory-based testing demonstrates that combining of up to 20 nasal swab specimens per pool can expand surveillance with antigen tests, even if a pool contains only one positive sample.