Progress has been made in the prevention and treatment of community-acquired bacterial meningitis during the past three decades but the burden of the disease remains high globally. Conjugate vaccines against the three most common causative pathogens (Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae) have reduced the incidence of disease, but with the replacement by non-vaccine pneumococcal serotypes and the emergence of bacterial strains with reduced susceptibility to antimicrobial treatment, meningitis continues to pose a major health challenge worldwide. In patients presenting with bacterial meningitis, typical clinical characteristics (such as the classic triad of neck stiffness, fever, and an altered mental status) might be absent and cerebrospinal fluid examination for biochemistry, microscopy, culture, and PCR to identify bacterial DNA are essential for the diagnosis. Multiplex PCR point-of-care panels in cerebrospinal fluid show promise in accelerating the diagnosis, but diagnostic accuracy studies to justify routine implementation are scarce and randomised, controlled studies are absent. Early administration of antimicrobial treatment (within 1 hour of presentation) improves outcomes and needs to be adjusted according to local emergence of drug resistance. Adjunctive dexamethasone treatment has proven efficacy beyond the neonatal age but only in patients from high-income countries. Further progress can be expected from implementing preventive measures, especially the development of new vaccines, implementation of hospital protocols aimed at early treatment, and new treatments targeting checkpoints of the inflammatory cascade.

Young people aged 10-24 years constitute 24% of the world's population; investing in their health could yield a triple benefit-eg, today, into adulthood, and for the next generation. However, in physical activity research, this life stage is poorly understood, with the evidence dominated by research in younger adolescents (aged 10-14 years), school settings, and high-income countries. Globally, 80% of adolescents are insufficiently active, and many adolescents engage in 2 h or more daily recreational screen time. In this Series paper, we present the most up-to-date global evidence on adolescent physical activity and discuss directions for identifying potential solutions to enhance physical activity in the adolescent population. Adolescent physical inactivity probably contributes to key global health problems, including cardiometabolic and mental health disorders, but the evidence is methodologically weak. Evidence-based solutions focus on three key components of the adolescent physical activity system: supportive schools, the social and digital environment, and multipurpose urban environments. Despite an increasing volume of research focused on adolescents, there are still important knowledge gaps, and efforts to improve adolescent physical activity surveillance, research, intervention implementation, and policy development are urgently needed.

Pre-Olympic Games predictions commonly include an increase in population-based physical activity in the host city, as often stated in the bid, but the post-Olympic Games effects on physical activity have not been summarised. In this Series paper, we aim to do the following: examine mentions of a physical activity legacy in pre-Olympic bid documentation; analyse existing physical activity surveillance data collected before, during, and after the Olympic Games in hosting areas around the world; and evaluate Google Trends data surrounding the London 2012 Olympic Games as a case study of community interest in the topic of exercise during the time of the Olympic Games. Before 2007, little mention of physical activity was made in pre-Olympic Games documentation, but, after that, most documents had targets for population physical activity or sports participation. The synthesis of available surveillance data indicates that there was no change in the prevalence of physical activity or sports participation, except for the 2008 Summer Olympics in Beijing and the 1998 Winter Olympics in Nagano; although, the increase in participation in Nagano might not be attributable to the Olympic Games since there was no change in participation in winter sports. The Google Trends data showed an acute spike in searches with the term "Olympic" immediately associated with the London Olympic Games period and showed a sustained peri-Olympic increase in searches with the term "exercise". By themselves, the Olympic Games have not improved population-wide physical activity but might be an important missed public health opportunity. Such a legacy will require strategic planning and partnerships across the International Olympic Committee and the Olympic, sport, and public health agencies and a thorough evaluation framework implemented throughout the pre-Olympic Games and post-Olympic Games period in the host country.

Approximately 1·5 billion people worldwide live with a physical, mental, sensory, or intellectual disability, about 80% of which are in low-income and middle-income countries. This Series paper provides a global overview of the prevalence, benefits, and promotion policies for physical activity for people living with disabilities (PLWD). PLWD are 16-62% less likely to meet physical activity guidelines and are at higher risk of serious health problems related to inactivity than people without disabilities. Meta-analyses have shown that physical activity has beneficial effects on cardiovascular fitness (average standardised mean difference [SMD] 0·69 [95% CI 0·31-1·01]), musculoskeletal fitness (0·59 [0·31-0·87]), cardiometabolic risk factors (0·39 [0·04-0·75]), and brain and mental health outcomes (0·47 [0·21-0·73]). These meta-analyses also show that health benefits can be achieved even with less than 150 min of physical activity per week, and suggest that some physical activity is better than none. Meta-analyses of interventions to increase physical activity for PLWD have reported effect sizes ranging from SMD 0·29 (95% CI 0·17-0·41, k=10) to 1·00 (0·46-1·53, k=10). There is increasing awareness among policy makers of the needs of PLWD for full participation in physical activity. Physical activity action plans worldwide must be adequately resourced, monitored, and enforced to truly advance the fundamental rights of PLWD to fully participate in physical activity.

The COVID-19 pandemic priorities have focused on prevention, detection, and response. Beyond morbidity and mortality, pandemics carry secondary impacts, such as children orphaned or bereft of their caregivers. Such children often face adverse consequences, including poverty, abuse, and institutionalisation. We provide estimates for the magnitude of this problem resulting from COVID-19 and describe the need for resource allocation.