As the COVID-19 pandemic is contained, another disaster is spreading faster than anticipated and threatening our future. With each passing day, our lives are being taken over a little more by global climate change. Nations around the world are struggling to withstand the damage brought on by disasters. They are working to put out forest fires, repair the damage floods have done to roads and homes, and learn how to exist in a warmer and riskier world. There is a new danger, albeit underestimated: the relationship between infectious diseases and global climate change. A comprehensive meta-analysis leads to the conclusion that climate warming may worsen more than 50% of known human diseases, and unfortunately this is happening now.
It has been less than two years since the last major outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron version was reported. Others, such as Plasmodia parasites (which cause malaria) and Vibrio cholerae (which cause cholera), have been known for years, while some, such as mpox and chikungunya virus, are less well known. In fact, as the climate continues to warm, it's possible that microbes that were frozen in frozen soil and currently have no antibodies may become active. This idea can be seen as alarming. And some people may believe that neither epidemics nor global climate change is real, or that both will pass. However, we have ample evidence that global climate change is causing disease outbreaks.
Climate risks can exacerbate infectious diseases in a variety of ways, both directly and indirectly. These include gradual temperature increases, environmental changes that accelerate the spread of disease-carrying insects, rodents and ticks, and sudden occurrences of events such as floods that contaminate drinking water supplies and displace pathogen-carrying people and animals.
As temperatures slowly rise, the likelihood of disease transmission is also changing, as some disease vectors can thrive in warmer environments. For example, the tiger mosquito (Aedes albopicus), which spreads new virus outbreaks, is becoming common in southern Europe. A British woman who visited France last year contracted the mosquito-borne dengue virus. Paraguay has had an unexpectedly large outbreak of chikungunya virus this year, with more than 120.000 confirmed cases of the disease. The virus had not previously caused a major outbreak or death in Paraguay, but this event killed 46 people, including newborns, and significantly deteriorated the health of the country as it spread to all states. The outbreak coincided with Paraguay's highest-ever average temperatures. The 2017 outbreak of chikungunya in Italy and the current increase in dengue virus infections in France have been attributed to a similar temperature rise in southern Europe.
Saad Omer, Director of the Yale Institute for Global Health, argues that “with global climate change, more and more areas are becoming mosquito-friendly, even far from the equator or at relatively high altitudes.” This comment is in response to local reports of malaria cases in Florida and Texas this year.
Outbreaks increase as a result of abnormal weather conditions and natural disasters. These usually spread within a few days or weeks and can catch regions and nations off guard. Dealing with such disasters tends to get worse as infectious diseases begin to spread. Two deadly cholera epidemics in 2022 and 2023 attracted the attention of the whole world. The first occurred after severe flooding in Pakistan and resulted in millions of infections. Worryingly, the strain that originated in Pakistan has been described as the deadliest cholera epidemic in Malawi's recorded history. Although only a few hundred cases of cholera are recorded in Malawi generally per year, there were 2022 confirmed cases and 2023 deaths between 57.414 and 1733. The high death rate of over 3% in this outbreak has stunned the medical community around the world, according to the Médecins Sans Frontières team working in Malawi.
In an increasingly globalized world, the challenges of global climate change and epidemics may be exacerbated by the movement of people, animals and businesses. Highly infectious diseases can easily cross borders despite strict travel restrictions, as evidenced by the rapid spread of SARS-CoV-2 variants. This means that if conditions are right for transmission, diseases can enter the environment undetected and cause epidemics. For example, cases from India were found to be responsible for the 2017 chikungunya virus outbreak in Italy.
Climate change can also force population migration, increasing human-wildlife contact and the danger of pathogen spread. Due to the El Nio event (a climate phenomenon that causes warming of surface waters in the eastern Pacific Ocean), scientists predict 2024 will be an even warmer year. In some parts of the world this will likely result in severe drought, which could lead to widespread migration.
The relationship between communicable diseases and global climate change should prompt governments and scientists to consider the possibility that pandemics and epidemics will be exacerbated by global climate change. Public health measures to mitigate epidemics should definitely be included in emergency responses to climate disasters. The worldwide movements of people, animals and merchandise must also be considered, as health systems must adapt to changing patterns of disease transmission. All of these initiatives require funding towards the intersection of epidemic prevention and combating global climate change. For example, the CLIMADE consortium has started to work in this direction. Of course, most importantly, this perspective needs to be adopted by the global community.
Will climate change increase epidemics and lead to pandemics? Definitely yes, if we just keep waiting without doing anything.
📩 31/08/2023 15:39