Rising global temperatures, particularly in warmer climates, influence dengue as they promote the growth and reproduction of Aedes mosquitoes, the primary vectors responsible for spreading the disease (13). “Monthly increases of 1°C in temperature increased the population risk of dengue by 1.95 times” (13). Dengue is highly concentrated in tropical areas and is therefore strongly correlated with temperature and the rainy season (13). In 1950, the number of global cases was approximately 908 (14), which increased to 250,000 annual cases between 1970 and 1980 (15). In 2016, a total of 291,964 cases were globally reported (16). As of 2024, there are over 7.6 million cases of Dengue globally (17).

Malaria is also a mosquito-borne disease found in warmer climates transmitted from the female Anopheles mosquito to humans. “Each 2°C–3°C increase in ambient environmental temperature increases malaria transmission by 3%–5%” (18). Anopheles mosquitoes thrive in warmer climates at lower altitudes, as their reproductive phases are shortened and their feeding frequencies are increased (18). Additionally, heavy precipitation is favorable for Anopheles living conditions, as in dry conditions, these mosquitoes will desiccate (19). Anopheles mosquitoes are at their most reproductive when a rainy season has just come to an end, as the water level decreases and water pools in areas with deformed terrain become prime for breeding (19). Global deaths caused by Malaria increased from 995,000 in 1980 to 1,817,000 in 2004 (20). As of 2021, there were 247 million cases of malaria globally (21).

Yellow fever is a viral hemorrhagic fever transmitted by infected A. Aegyptus mosquitoes (22). There is strong evidence that the predicted global warming will alter the international distribution of A. Aegyptus and increase the risk of the disease globally (23). Factors that influence and improve the occurrence of Yellow Fever include increased rainfall, higher air humidity and temperature, as well as non-primate human species, which serve as hosts for this disease (24). The mosquitoes carrying this disease have a peak population during a rainy summer, as increased rainfall and temperature (24) contribute to their proliferation. As of 1975, only 168 cases were reported in South America (25). In 2000, the global incidence rate of Yellow Fever was 0.4 per 1,000,000 total population (with 699 total cases reported in 2000) (26). In 2021, there were an estimated 86,509 cases reported globally (27).

Influenza is an airborne, transmitted viral disease (28) that is strongly influenced by absolute humidity, which in turn is affected by environmental temperature (29). At low temperatures, drier conditions promote the spread of the influenza virus (29). This occurs because cold temperatures make the viral envelope more fragile, and dry air helps the virus remain stable, allowing it to stay airborne for more extended periods and increasing its ability to spread (29). On the other hand, at high temperatures, higher humidity levels are more favorable for the virus's survival (29). In warm conditions, the virus is more likely to dry out; however, high humidity helps prevent this, keeping the virus viable for longer periods and facilitating its spread (29). In 1950, a total of 164,352 patients were diagnosed with influenza in the United States (30). As of 2010, the annual rate of fatalities due to Influenza was∼1.4–16.7 deaths per 100,000 persons (31). Currently, as of 2024, Influenza affects approximately 8% of adults and 25% of children annually (32).

HIV is a viral infection caused by the human immunodeficiency virus and is spread by exposure to blood or other bodily fluids through sexual and mother-to-infant contact (33). Climate change has been linked to HIV transmission through its effects on public health, including increased food insecurity and greater human migration or climate refugees (34). Food insecurity is related to climate change as it increases substance use, resulting in a driving force for sexually risky behaviors (34). The chain of events begins with climate change-induced land degradation, followed by a reduction in food production. Then, those living in poverty may resort to desperate measures to seek food, possibly including transactional or forced sex, which raises the risk of HIV transmission (35). The first known case of HIV was reported in 1959 in Congo (36). In 2000, the total number of global cases in December 2000 was 36.1 million (37). As of 2023, there were an estimated 39.9 million global cases (38).

Monkeypox is a viral disease caused by a pox virus, a member of the genus Orthopoxvirus (39). Climate change, resulting in a warmer climate, is predicted to lead to changes in the geographic ranges at risk of Monkeypox, caused by direct climate effects on the pathogen or indirect effects on species that harbor the pathogen or vector species (40). Warmer temperatures are found to be much more apt for human MPX (40). “Specifically, for each 1°C increase in the heat index (HI), daily cases increased by 7.7%” (41). Conversely, an increase in wind speed has been found to decrease monkeypox cases (41). The first case of monkeypox was diagnosed in 1970 in a 9-month-old African baby (42). In 2007, the average incidence rate worldwide was 5.53 per 10,000 individuals (43). As of 2024, over 100,000 confirmed cases had been reported by 120 countries worldwide (44). Table 1 summarizes the climate-related incident rate of epidemics over the last 75 years.

In response to the emergence of dengue as an epidemic in more than 100 countries, in 2024, the World Health Organization launched the Global Strategic Preparedness, Readiness and Response Plan (SPRP) (64). Their aim is, and has been, to coordinate a global response. Their plan involves 5 primary tenets: (1) Emergency coordination (setting up a team with leaders to handle the situation), (2) Collaborative surveillance: creating tools to quickly spot and control outbreaks of Dengue (within the lab), (3) Community protection (working closely with communities to share information and prevention strategies), (4) Safe and Scalable Care (ensuring health services are equipped to provide adequate care to patients with dengue, and (5) Access to countermeasures (continuing ongoing research to find better treatments and vaccines) (64). Due to the rapid global spread of dengue, the WHO has also employed a risk mapping strategy to assess which countries are currently at risk of dengue and which countries are vulnerable to the onset of dengue transmission (64). Their objective in using the risk map was to pinpoint countries where preparedness and response interventions were required, and in such cases, these countries would be registered for increased surveillance (64). WHO has also adopted the approach of using vector control strategies, including removing breeding sites and employing chemical agents to kill the larvae of Aedes Mosquitoes (64). The World Health Organization is aware of the role that climate change plays in the increase of dengue cases and is therefore adjusting dengue control methods based on different levels of risk, considering how changing climate patterns may impact the location of mosquito breeding sites (64). The SPRP is in the stages of developing an efficient diagnostic test, efficient treatments options and a vaccine for prevention (64). There have been dengue vaccines released in the past, such as Dengvaxia and Qdenga, and another more efficient dengue vaccine is currently in the middle of clinical development (64). The WHO has recommended the dengue vaccine for routine immunization programs in areas with high transmission rates and where dengue is a major public health concern, specifically for children aged 9–16 years (64).

As Malaria emerges as a more prevalent disease globally, the World Health Organization administered the Global Technical Strategy for Malaria 2016–2030 (65). Their objective is to reduce the global malaria rates by 90% by 2030 (65). WHO plans to eliminate malaria from countries in which malaria was prevalent in 2015 in at least 20 of such countries by 2025, and at least 35 of those countries by 2030 (65). The malaria eradication strategy is based on five key principles: tailoring approaches to local needs, strong leadership and community involvement, enhanced data tracking, equitable access to health services, and innovation in new tools to accelerate progress towards elimination (65). WHO also emphasizes the importance of vector control strategies in eradicating malaria, utilizing tools such as long-lasting insecticidal nets and indoor spraying (65). Research is needed to figure out where and how targeting the parasite reservoir can help reduce malaria (65).

The long-term (2017–2026) global strategy of the World Health Organization to “Eliminate Yellow Fever Epidemics” (EYE) focuses on three main goals: “(1) protecting at-risk populations, (2) preventing international spread, and (3) containing outbreaks quickly” (66). The strategy includes recommendations of vaccination, building resistant cities that are ready for emergencies and making sure international health rules are followed more effectively (66). The EYE strategy exclusively targets countries that are at the highest level of risk for a yellow fever outbreak (66). In the next ten years, vaccine makers are expected to provide 1.38 billion doses (66). Also, the WHO has adopted the Integrated Disease Surveillance and Response (IDSR) program to obtain a data count of suspected, probable, and confirmed yellow fever cases (66). By the end of 2025, WHO suspects that all high-risk countries in Africa can now test and confirm yellow fever and by the end of 2026, all high-risk countries will have completed national vaccination campaigns (66).

In June 2024, the Center for Disease Control and Prevention (CDC) launched the Global Influenza Program (67). CDC is teamed up with global partners to improve their response to Influenza threats (67). Their programs core tenets are to work with partners to improve flu surveillance, develop pandemic plans (and prevention plans), support research projects, and expand flu vaccination programs (67). As well, CDC is partnered with the World Health Organization to monitor seasonal flu, detect novel flu and work on a vaccine (67). The WHO predicts that by 2030, we will have better global tools, including a specific plan with more research devoted to preventing, detecting, controlling, and treating influenza, along with stronger country capacities, where each country will have its own customized influenza program, ensuring global health preparedness (68).

By the end of 2025, Canada's global target is to have 95% of people living with HIV diagnosed, and 95% of those diagnosed on treatment, along with 95% of those on treatment responding positively to the treatment with reduced viral load of HIV (69) The Global Health HIV Prevention Clinic (GPC) also launched the HIV prevention strategy 2025 in which they predict to have fewer than 370,000 annual new cases of HIV by the end of 2025 (70). The road map that GPC created includes 10 steps: (1) conduct assessments and gather data on HIV prevention programs; (2) adopt a precise prevention approach focused on target populations; (3) identify the country's financial investment needs for adequate HIV responses; (4) strengthen leadership for HIV prevention by promoting collaboration, oversight, and management; (5) boost community-led HIV prevention services; (6) eradicate social and legal barriers to HIV prevention services for target populations. (7) integrate HIV prevention into key services to improve outcomes; (8) create systems to introduce new HIV prevention tools and innovations quickly; (9) set up real-time monitoring systems for prevention programs with regular updates; and (10) improve accountability for everyone involved in HIV prevention progress (70). Their actions focus on combination prevention for key groups, like adolescent girls, young women, men, and boys in high-risk areas, promoting condoms and lubricants and expanding access to antiretroviral prevention, including PrEP (Pre-exposure Prophylaxis) (70).

As of 2024, the World Health Organization has launched the Global Strategic Preparedness and Response Plan to combat the outbreak of monkeypox (71). Their plan focuses on implementing robust surveillance, prevention, and response strategies; enhancing access to medical tools such as tests and vaccines; reducing animal-to-human transmission; and engaging communities in outbreak control (71). The WHO is actively working on an efficient vaccine for individuals who are the most vulnerable, specifically healthcare workers in contact with recent cases (71). Globally, the focus is on strong leadership, timely guidance, and providing medical tools to high-risk groups in affected countries (71). In Africa, WHO Regional Office (AFRO) and Africa CDC will lead the mpox response, using a shared plan and budget (71). At the national and local levels, health authorities will adjust strategies based on the current situation (71). Currently, there is no specific antiviral treatment for Monkeypox, which is a growing global concern (72).

Reducing exposure to climate hazards can be achieved by preventing them in the first place, which starts with increased awareness and education regarding the threat of climate change. A recent study conducted on 2,273 participants in more than 30 countries revealed a strong correlation between people's belief in climate change and their willingness to make behavioral changes to mitigate it (80). Furthermore, according to the American Journal of Health, only one in five Americans reports having a strong understanding of climate change (81). Moreover, roughly half of Americans express distrust of related media coverage.

Moving beyond essential awareness, citizens can further mitigate the risk of climate change exposure by supporting government policy change, as well as reducing their carbon footprint (82). Although broad public support is not always a prerequisite for implementing policies designed to reduce greenhouse gases, it has been demonstrated to facilitate the adoption and implementation of robust policies (82).

On a personal level, individual citizens can take simple steps to reduce their carbon footprint, such as using public transportation, reducing waste, conserving water, and eating a more plant-based diet (83). Environmental studies have shown that daily household consumption is the primary contributor to greenhouse gases, accounting for two-thirds of global carbon emissions (83). When undertaken collectively, individual actions can contribute to the broader effort of mitigating the long-term impact of climate change.

Sensitivity to the societal impacts of current climate change can be influenced by a multitude of factors directly related to health and well-being, including socioeconomic status, biology and genetic endowment, access to health services, gender, and personal health practices (79). Similar to mitigating the risk of exposure, individuals can help lower sensitivity to climate change-driven health threats by raising personal awareness and supporting community initiatives (79).

One type of public initiative to reduce climate change sensitivity is creating more resilient infrastructure to reduce the impact of climate change, such as “the designing of flood-resistant homes, improving waste management systems, or building more green spaces can limit the conditions that foster disease outbreaks, particularly in vulnerable populations” (84). Unfortunately, the current reality is that longer-term climate-related risks are not always taken into account in the shorter-term profit-focused public and private investment decisions. As a result, consequently, data shows that large amounts of capital continue to flow into hazard-prone areas (84).

Another form of public initiative to reduce climate change sensitivity is to ensure disaster preparedness. Providing immediate aid, setting up shelter, ensuring clean water, and managing sanitation can help reduce the risk of secondary diseases following a natural disaster.

Adaptive capacity is “the potential or ability of a system, region, or community to adapt to the effects or impacts of climate change” (85). Communities that have established high adaptive capacity, as evidenced by comprehensive plans and responses, have been shown to provide citizens with a better ability to protect their own health (79). Human adaptation is crucial in mitigating the socio-economic impacts of climate change on ecosystems and populations (86). Non-medical citizens can also strengthen these measures through education and support.

A prime example of adaptive behavior is the water management initiatives under way in the UK (87). UK researchers are using climate change factors to predict future alterations in rainfall and river flow. These estimates are then incorporated into the long-term plans of water utility companies to ensure the sustainability of water supply (87).

As climate change influences the spread of vector-borne diseases such as malaria, dengue, and Zika, personal adaptive health measures that citizens can employ include limiting exposure (using insect repellent and wearing protective clothing when outdoors), eliminating areas of standing water, and using bed nets when sleeping (88). As an example of the effectiveness of one of these solutions, the World Health Organization (WHO) estimated that between 2000 and 2015, the annual incidence of malaria cases fell by 37% and that the malaria mortality rate fell by 60% (88) These reductions are believed to have been attained, in large part, due to the increase in the use of insecticide-treated bed nets and access to treatment. However, the WHO also indicated that only about 68% of individuals at risk of malaria slept under an insecticide-treated bed net in 2015, so the reduction in malaria could have been even more significant with improved precautions.

For viral-based or waterborne diseases, personal adaptive measures could include regular hand washing, boiling potentially unsafe water, and/or avoiding drinking from unknown sources. The U.S. Centers for Disease Control and Prevention has cited hand washing as the single most effective way to prevent the transmission of disease (89).

Although climate patterns highly influence the transmission of dengue, it has been shown that dengue cases are not always consistently distributed in cities where climate is considered uniform (90). Therefore, there are other confounding factors at play in the outbreak of dengue (90). Such factors include socioeconomic statuses (SES), population growth, mass human movements, and urbanization (90). A study done in Nouméa during two major dengue epidemics (2008–2009 and 2012–2013) reveals that the neighborhoods with lower socioeconomic statuses were correlated with higher dengue incidence rates (90). Rapid urbanization has been found to play a large role in the outbreak of dengue, as it enables easier distribution of the Aedes population (91). Urban developments are creating more suitable habitats for Aedes mosquitoes, such as highly concentrated areas of human density, which provide more opportunities for blood feeding, and increased areas of moisture, like flowerpots (91). Ultimately, it is not only climate change that plays a role in the increase of dengue, but multiple variables are at play in this disease's transmission.

For malaria, it appears that areas of large human densities contribute to a decline in the spread of malaria (92). This is because urbanization and anthropogenic factors create a less suitable breeding ground for Anopheles mosquito species (92). These anthropogenic variables include fewer water surfaces for breeding and natural surfaces covered with infrastructure (92). Additionally, urbanization contributes to increased pollution, which negatively impacts breeding sites for Anopheles species (92). Other anthropogenic factors that contribute to the spread of malaria include agriculture (93). For instance, when farmers construct irrigation channels, this appears to create suitable mosquito breeding sites (93). Lastly, low socioeconomic factors also contribute to an increase in malaria cases, as those with lower socioeconomic statuses will have less access to health care and risk prevention (94).

Other confounding factors that contribute to an increase in Yellow Fever outbreaks include social, ecological, and behavioural factors (95). Such factors include the movement of human populations into forest areas and coastal zones, where there is an increased number of breeding sites for Aedes aegypti mosquitoes (95). The number of non-vaccinated human populations also plays a role in the spread of Yellow Fever (95). It appears that urbanization has caused an increase in Yellow Fever outbreaks (96). According to WHO, an outbreak in Angola in 2016 was due to a large urban outbreak in a transportation center, which showed how Yellow Fever can rapidly spread to foreign nations (96). In Africa, growing and increasingly populated cities (increasing by 4% annually) appear to play a role in the increase of Yellow Fever, as unvaccinated populations are exposed to drinking water in large open containers—favourable breeding sites for Aedes aegypti mosquitoes (97). Fortunately, public health initiatives like Oswaldo Cruz's campaign against the mosquito vector Aedes aegypti drastically reduced Yellow Fever cases in Rio de Janeiro (95). In the early 1940s, both vaccination campaigns and the eradication of Aedes aegypti significantly contributed to the elimination of urban Yellow Fever transmission in Brazil and across the Americas (95).

Aside from climate change contributing to the spread of influenza, other impacting factors like urbanization have a major effect on the intensity of influenza epidemics (98). Urbanization shapes the severity of influenza's transmission patterns due to increased human population densities, which increase human contact and population mobility (98). It appears that cities are the principal areas for human influenza transmissions, with more diffuse epidemics occurring in more populated cities, as there are higher rates of personal contact (99). It also appears that in smaller cities, surges of influenza outbreaks last shorter periods of time (99). Regarding the public health interventions that were set in place during the peak of COVID-19, this decreased the cases of influenza from 71.9 per 1,000 people to 49.8 per 1,000 people (100). Such public health interventions included remaining at home when experiencing respiratory symptoms, wearing masks in public spaces, and hand sanitization (100).

A strongly contributing factor to the prevalence of HIV outbreaks is in-migration into large cities (101). Migration increases opportunities for contact between humans, growing sexual networks from different areas, and ultimately increasing HIV's transmission rate (101). According to the article “HIV/AIDS and Urbanization”, “urban levels of HIV infection are typically four to ten times those of rural areas” (102). Public health policies have helped reduce HIV cases in certain parts of the world, particularly in Africa, where the President's Emergency Plan for AIDS Relief was employed (103). It is thought that through advances in treatment, the HIV epidemic in the United States could be quickly ended (103).

Although the chances of Monkeypox outbreaks tend to increase in warmer climates, there are other variables that play a role in its transmission. The surge of Monkeypox cases in Nigeria in 2017 was driven by a combination of factors, including population growth and unvaccinated residents (104). Two key factors contributing to the outbreak were increased exposure of humans to forest animals due to deforestation and population migration, and declining vaccination immunity since the 1970s (104). Additionally, globalization has increased the likelihood that Monkeypox will spread around the world, as humans are more connected, giving way to quicker disease transmission (104).

Generally, there appears to be a strong correlation between high infection rates and urban areas (denser populations) (105). Another variable that has appeared to contribute to an increase in Monkeypox cases includes environmental pollution, such that air pollutants like CO and NO₂ have a positive association with daily Monkeypox cases (106).

Malaria continues to pose a significant health challenge around the world, yet we've made remarkable strides in reducing both the number of cases and deaths, especially with the advent of new vaccines. The recent malaria vaccines, particularly RTS, S/AS01 and R21/Matrix-M, have been instrumental in significantly lowering malaria cases among children in regions that bear the highest burden. Between 2000 and 2015, global malaria incidence rates experienced an impressive drop of 37%, and mortality rates decreased by an incredible 60%. This success is largely due to the increased use of insecticide-treated nets, enhanced diagnostics, and effective antimalarial treatments—vaccines came into play later, as they weren't widely accessible during this period (117, 118). In sub-Saharan Africa, an astonishing 70% of the reduction in cases can be credited to these vital interventions (117).

The impact of malaria vaccines on the incidence rate is truly remarkable. One shining example is the RTS S/AS01 vaccine, highly recommended for children living in high-transmission areas. This vaccine has shown that it can prevent a median of 2,653 malaria cases for every 100,000 people each year, and it has helped avoid around 82,270 cases in fully vaccinated children per 100,000 (119–121). In long-term studies, the number of severe malaria cases in vaccinated children has stayed impressively low, ranging from just 0.004 to 0.007 cases per person-year, with no notable rise in cases observed 6–7 years after vaccination (122). Additionally, the newer R21/Matrix-M vaccine has proven to be effective as well, showcasing 75% efficacy at seasonal sites and 68% at standard sites, leading to a decrease of 868 malaria cases per 1,000 child-years at seasonal sites and 296 per 1,000 at standard sites over the course of 12 months (118).

It is encouraging to observe that acceptance rates for malaria vaccines are notably high in endemic countries, attaining an impressive rate of 95.3%. This indicates substantial potential for achieving a widespread impact as these vaccines become increasingly accessible. Prior to the introduction of vaccines, the decline in malaria cases was primarily attributed to vector control measures and treatment protocols. However, the advent of vaccines such as RTS, S/AS01 and R21/Matrix-M has resulted in even more significant reductions in malaria cases among children, particularly in Africa. Given such elevated vaccine acceptance rates, we are optimistic about the ongoing advancements we can achieve in the fight against malaria.

Yellow fever is a serious viral disease found in various regions of Africa and South America. The introduction and expansion of yellow fever vaccination campaigns have made a remarkable difference, leading to significant reductions in cases and deaths around the world, especially in high-risk areas. Thanks to mass vaccination, we've seen a substantial decline in the incidence of yellow fever and outbreaks.

In Africa, these mass vaccination efforts have resulted in an impressive 47% reduction in yellow fever deaths in 2018 when compared to what might have happened without the vaccine, preventing around 10,000 deaths that year alone (123). Preventive mass vaccination campaigns (PMVCs) across African provinces have brought about an incredible 86% decrease in the incidence of yellow fever outbreaks (with an incidence rate ratio of 0.14), leading to a 34% reduction in outbreaks during the study period from 2005 to 2018 (124–131). Between 2005 and 2017, vaccination activities in Africa are estimated to have prevented between 3.3 and 6.1 million deaths over the lifetimes of those vaccinated, depending on the level of herd immunity considered (127).

Since 1970, global yellow fever vaccination coverage has improved significantly, yet as of 2016, 43%–52% of individuals in risk zones still needed vaccination to reach the recommended 80% coverage threshold for preventing outbreaks (125). While vaccination has been especially effective in high-risk areas, there are still gaps in some regions, particularly in certain parts of Nigeria, the Democratic Republic of Congo, and South Sudan (128).

Overall, yellow fever vaccination campaigns have had a significant impact, reducing cases, deaths, and outbreaks, particularly in Africa. However, we must continue our efforts to close these coverage gaps and maintain high immunity levels to prevent future outbreaks.

Vaccines play a vital role in keeping us healthy by consistently reducing cases of influenza, hospitalizations, and severe complications. The greatest benefits are seen in children and those in high-risk groups. In the United States from 2016 to 2018, influenza vaccination helped prevent up to 46.6 cases for every 1,000 vaccinated children (ages 6 months to 8 years) and 6.9 cases for every 1,000 vaccinated adults aged 65 and older during seasons when the vaccine effectiveness ranged between 29% and 40% (132). Over in Europe during the 2022/23 season, vaccine effectiveness against influenza A varied from 27% to 44% across all ages, with children benefiting the most at 49%–77%. For influenza B, vaccine effectiveness was impressive at over 50% overall, soaring to 87%–95% in children (133). In the US during the 2019/20 season, vaccination lowered the risk of influenza-related hospitalization by 41% in adults (132). A meta-analysis reveals that vaccine effectiveness among children is 39% for reducing medical visits and an excellent 57% for cutting down hospitalizations; for the elderly, it stands at 25% for visits and 14% for hospitalizations (134, 135).

Getting vaccinated against monkeypox, especially with the JYNNEOS vaccine, plays a vital role in minimizing the spread and impact of monkeypox outbreaks across the globe. While we don't have specific numbers showing the reduction in global cases before and after vaccination, there's clear evidence that the vaccine produces strong immune responses. These responses are expected to lead to lower case numbers and a lighter disease burden.

The JYNNEOS vaccine elicits a robust antibody response against monkeypox and related orthopoxviruses, with its peak response occurring approximately 2 weeks after the second dose, regardless of whether the individual has received prior vaccination (136). Most participants continued to have orthopoxvirus-specific antibodies for up to 2 years after vaccination, indicating that this vaccine provides long-lasting immune protection (136). It also effectively generates neutralizing antibodies, which are crucial for preventing infection and reducing transmission (136). Even though we don't have specific global case reduction rates detailed before and after vaccination, the strong immune response and the long-lasting presence of antibodies suggest that the JYNNEOS vaccination is likely making a significant impact in reducing monkeypox cases and helping to manage outbreaks.