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Nature ; 626(7999): 555-564, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38356065


The possibility that the Amazon forest system could soon reach a tipping point, inducing large-scale collapse, has raised global concern1-3. For 65 million years, Amazonian forests remained relatively resilient to climatic variability. Now, the region is increasingly exposed to unprecedented stress from warming temperatures, extreme droughts, deforestation and fires, even in central and remote parts of the system1. Long existing feedbacks between the forest and environmental conditions are being replaced by novel feedbacks that modify ecosystem resilience, increasing the risk of critical transition. Here we analyse existing evidence for five major drivers of water stress on Amazonian forests, as well as potential critical thresholds of those drivers that, if crossed, could trigger local, regional or even biome-wide forest collapse. By combining spatial information on various disturbances, we estimate that by 2050, 10% to 47% of Amazonian forests will be exposed to compounding disturbances that may trigger unexpected ecosystem transitions and potentially exacerbate regional climate change. Using examples of disturbed forests across the Amazon, we identify the three most plausible ecosystem trajectories, involving different feedbacks and environmental conditions. We discuss how the inherent complexity of the Amazon adds uncertainty about future dynamics, but also reveals opportunities for action. Keeping the Amazon forest resilient in the Anthropocene will depend on a combination of local efforts to end deforestation and degradation and to expand restoration, with global efforts to stop greenhouse gas emissions.

Florestas , Aquecimento Global , Árvores , Secas/estatística & dados numéricos , Retroalimentação , Aquecimento Global/prevenção & controle , Aquecimento Global/estatística & dados numéricos , Árvores/crescimento & desenvolvimento , Incêndios Florestais/estatística & dados numéricos , Incerteza , Recuperação e Remediação Ambiental/tendências
Trials ; 25(1): 105, 2024 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-38310290


Many research funders have invested billions of US dollars in building research capacity in sub-Saharan Africa (SSA). Despite these colossal investments, many well-intentioned and designed clinical research projects have either failed to kick off or ended abruptly. Although obstacles to clinical research in SSA are well known, there is limited information on frameworks and tools that can be used to anticipate and avert these systemic bottlenecks, particularly those related to socio-politics. In this paper, we leveraged lessons from entrepreneurs and development experts in harsh and uncertain business environments to develop a framework for anticipating and addressing potential bottlenecks to clinical research in SSA. More so, to illustrate and build a case for this framework, we shared our experience in supporting clinicians and regulators to adopt a point-of-use care tool, the "chemoPAD," to screen for the quality of anticancer medications rapidly and systematically in Cameroon despite resistance from some stakeholders. The critical steps in this framework involve identifying stakeholders, categorizing them based on their potential reactions to the study (adversary, supporters, and indifferents), and developing critical strategies to engage or deal with each stakeholder's reactions, starting with adversaries. This approach may be useful in complex research projects, especially clinical trials, which often involve many stakeholders with different interests and perceptions.

Pesquisa Biomédica , Humanos , África Subsaariana , Pesquisa Biomédica/economia , Pesquisa Biomédica/tendências , Fortalecimento Institucional , Empreendedorismo
JAMA ; 331(6): 482-490, 2024 02 13.
Artigo em Inglês | MEDLINE | ID: mdl-38349371


Importance: Repeated mass distribution of azithromycin has been shown to reduce childhood mortality by 14% in sub-Saharan Africa. However, the estimated effect varied by location, suggesting that the intervention may not be effective in different geographical areas, time periods, or conditions. Objective: To evaluate the efficacy of twice-yearly azithromycin to reduce mortality in children in the presence of seasonal malaria chemoprevention. Design, Setting, and Participants: This cluster randomized placebo-controlled trial evaluating the efficacy of single-dose azithromycin for prevention of all-cause childhood mortality included 341 communities in the Nouna district in rural northwestern Burkina Faso. Participants were children aged 1 to 59 months living in the study communities. Interventions: Communities were randomized in a 1:1 ratio to receive oral azithromycin or placebo distribution. Children aged 1 to 59 months were offered single-dose treatment twice yearly for 3 years (6 distributions) from August 2019 to February 2023. Main Outcomes and Measures: The primary outcome was all-cause childhood mortality, measured during a twice-yearly enumerative census. Results: A total of 34 399 children (mean [SD] age, 25.2 [18] months) in the azithromycin group and 33 847 children (mean [SD] age, 25.6 [18] months) in the placebo group were included. A mean (SD) of 90.1% (16.0%) of the censused children received the scheduled study drug in the azithromycin group and 89.8% (17.1%) received the scheduled study drug in the placebo group. In the azithromycin group, 498 deaths were recorded over 60 592 person-years (8.2 deaths/1000 person-years). In the placebo group, 588 deaths were recorded over 58 547 person-years (10.0 deaths/1000 person-years). The incidence rate ratio for mortality was 0.82 (95% CI, 0.67-1.02; P = .07) in the azithromycin group compared with the placebo group. The incidence rate ratio was 0.99 (95% CI, 0.72-1.36) in those aged 1 to 11 months, 0.92 (95% CI, 0.67-1.27) in those aged 12 to 23 months, and 0.73 (95% CI, 0.57-0.94) in those aged 24 to 59 months. Conclusions and Relevance: Mortality in children (aged 1-59 months) was lower with biannual mass azithromycin distribution in a setting in which seasonal malaria chemoprevention was also being distributed, but the difference was not statistically significant. The study may have been underpowered to detect a clinically relevant difference. Trial Registration: Identifier: NCT03676764.

Antibacterianos , Azitromicina , Mortalidade da Criança , Malária , Humanos , Azitromicina/provisão & distribuição , Azitromicina/uso terapêutico , Burkina Faso/epidemiologia , Quimioprevenção/métodos , Quimioprevenção/estatística & dados numéricos , Mortalidade da Criança/tendências , Malária/epidemiologia , Malária/mortalidade , Malária/prevenção & controle , Antibacterianos/provisão & distribuição , Antibacterianos/uso terapêutico , Estações do Ano , Lactente , Pré-Escolar