TODAY we conclude our two-part series on the impact of global warming on health, highlighting the compounding issues of inequality and vulnerability and the need to have viable public health interventions and mitigation strategies to protect vulnerable individuals and communities.

Inequality and vulnerability

Climate change exacerbates inequalities, such as those driven by systemic economic injustice and disproportionately affect poor and marginalised communities. Persons living in less developed countries bear the greatest burden of most vector-borne diseases, a circumstance that reinforces health inequities and impedes socio-economic development. Poverty, poor environmental conditions, inadequate housing and living conditions, and limited access to affordable quality health services exacerbate the effect. Children and the poor are particularly susceptible, owing in part to the effects of malnutrition; women and the elderly are also at increased risk. Vector-borne diseases during pregnancy are associated with particularly poor health outcomes among mothers and newborns from low-income or otherwise disadvantaged groups, as evidenced by the devastating effects of congenital infection with Zika virus during the explosive epidemic of Zika virus infection (which was spread by aedes mosquitoes) in Brazil in 2015.

Public health interventions

Improvements in the public awareness, detection, prevention, and treatment of vector borne diseases have been driven by investments in surveillance and control and form the basis of adaptation strategies for a changing climate. Appropriate specific measures vary according to disease, pathogen life cycle, and the level of risk and may include a combination of climate-informed, early-warning systems, enhanced and new land-use management strategies, improved access to prevention measures (eg, biologic mosquito control, personal protective measures, insecticides, and vaccines), and new and improved therapies. For public health interventions to have a successful outcome, there must be timely and adequate stakeholder engagement, community and household acceptance and equally important, appropriate, and sustainable long-term funding mechanisms. A 2017 survey of 1,083 US vector-control programmes showed that 84 per cent of the programmes were rated as “needs improvement” in one or more core competencies (eg, insecticide-resistance testing). The same year, the Centers for Disease Control and Prevention (CDC) established five regional centres of excellence to help respond to emerging vector borne diseases and to help create a new generation of vector experts.

Malaria highlights several challenges that can occur in the implementation of adaptation strategies. After two decades of concerted international and national investment and consistent declines in malaria cases and malaria-related deaths, worldwide funding has stagnated; malaria is now resurgent in several countries, owing in part to increasing drug and insecticide resistance. This has been worsened to some degree by service and supply chain disruptions resulting from the COVID-19 pandemic. Innovations and leadership are needed to keep up with biologic and socio-economic challenges and to ensure equitable access to high-quality treatment in low- and middle-income countries.

The prevention of dengue and West Nile virus infection relies mainly on community-level mosquito-control programmes; the implementation of such programmes varies according to several factors, including funding and operational management. Avoidance of the vector habitat during the transmission season as a result of public communication has long been an important prevention strategy for Lyme disease. Various personal protective measures (eg, insect repellent and protective clothing) and tick-control strategies (eg, the culling of deer) have been proposed as approaches to reduce the risk of Lyme disease, but evidence of effectiveness is generally lacking.

Vaccines have been successful in the prevention of three vector-borne diseases: yellow fever, Japanese encephalitis, and tick-borne encephalitis. Unfortunately, vaccines approved for malaria and dengue in the past several years have had only limited success. Scientists continue to work on developing new and more effective vaccines that target vector borne diseases with some promise. A recent phase 2 trial in Mali (West Africa) showed the effectiveness of a single infusion of a monoclonal antibody against Plasmodium falciparum infection over a six-month follow-up period during malaria season. Also promising is a new dengue vaccine which has shown promise in a phase three trial and regulatory approval by European authorities is being sought.

According to the Intergovernmental Panel on Climate Change, successful vaccine development and uptake have the potential to substantially offset the effect of climate change on vector borne diseases. There remains some challenge though with combating vaccine hesitancy which has become more pronounced since the COVID-19 pandemic.

Better surveillance data and early-warning systems are critical to enhance public awareness, facilitate the targeting of resources (human and financial) for improved responses, and identify knowledge gaps and research needs. Adaptation plans must be time-sensitive, culturally sensitive and context-specific while also considering factors such as shifting disease patterns, extreme weather events, and current and future climate variations and trends. This approach will require collaboration among various sectors, such as national and local health authorities, civic society groups, affected communities, urban planners, and climate experts.

Implications for clinical practice

With increased international travel, there is limited geographic confinement of any transmissible vector-borne illness. Increasing prevalence in any geographic locations puts the entire global community at risk. It is only a question of time before any vector-borne illness in one location is seen in other locations, as long as global warming creates the requisite environment. Improved education of health-care professionals and community workers is needed with respect to specific vector borne diseases, particularly in regions in which diseases are newly emerging or anticipated to emerge. In many locations, clinicians are likely to see more cases of vector borne diseases during longer transmission seasons, especially in regions with historically low levels of transmission. Awareness of local changes in disease rates and travel histories will be helpful in the evaluation process. The non-specific clinical manifestations of many vector borne diseases often make diagnosis difficult. Strategies for the prevention and treatment of vector-borne diseases should be reviewed regularly and systematically. To help address the additional burden of health care delivery created by a changing climate, health professionals can advocate for more climate-resilient health systems and for programs that focus on the current worldwide shortages of health professionals, including infectious-disease experts.

Mitigation of climate change

Reducing the risks of vector borne diseases and other health consequences of climate change requires not only adaptation but also a rapid and equitable transition from fossil fuels to more environmentally friendly alternative energy sources. The global carbon footprint currently is largely driven by emissions in the West. It is important that decarbonisation of climate is not done in a way that is detrimental to developing countries or impedes industrialisation and economic development in countries that are already severely underdeveloped. The current push to stagnate development in poorer countries is misguided.

The signing of the Inflation Reduction Act of 2022 represents a necessary (although insufficient) move toward decarbonising the US economy in line with the goals set under the Paris Agreement in 2015. The health-care sector, which contributes an estimated 4.9 per cent of the total carbon footprint worldwide, must be part of the process. As trusted voices, health professionals can weigh in regarding the importance and urgency of mitigation.

Conclusions

Climate change has substantial effects on pathogens, vectors, and reservoir hosts, with implications for the health sector worldwide. Many vectors are already expanding their latitude and altitude ranges, and the length of season during which they are active is increasing; these trends are expected to continue as the climate continues to warm. Changes at the local level will be context- and disease-specific. Clinicians must be well informed and constantly alert to changes in risk for the population they serve.

To protect health and equity in a warmer world, investments are needed in vector control with respect to tailoring measures to rapidly emerging situations and in new forms of technology and approaches, including vaccines. Unfortunately, adaptation strategies will not be viable as a long-term solution without the implementation of sufficient, urgent mitigation efforts to maintain global temperatures below critical thresholds.

Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for the Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Send correspondence to info@caribbeanheart.com or call 876-906-2107