Why Are So Many Lethal Infectious Diseases On The Rise?

The alarming rise of Dengue in Peru is a climate change wake-up call that, if unchecked, could bring up more pandemics.

As the golden sun sets over the bustling streets of Lima, an invader too small to see but powerful enough to disrupt lives, the Aedes aegypti mosquito, is spreading across the country. This tiny pest, known for spreading the dengue virus, is causing a major health crisis. The number of deaths caused by dengue has tripled compared to the same period last year. In response, the government of Peru has declared a public health emergency to allow the government to mobilize significant economic resources to control the mosquito populations.

Dengue isn’t just a fever that brings discomfort; it’s a disease that, in its severe forms, can threaten lives, particularly the most vulnerable, like infants and pregnant women. The symptoms — ranging from nausea and rashes to potentially fatal internal bleeding — tell a story of a community under siege by an ever-adapting enemy. Health officials have been winding through Lima’s streets, spraying insecticides wherever standing water provides breeding grounds for mosquitoes — this includes flower vases in cemeteries and schools.

But this isn’t only a Peruvian story. This is a situation we should all watch closely. Because the crisis in Peru is a stark reminder of the broader implications of a warming planet and the diseases that thrive when climate changes. We all need to know how to act accordingly.

As we settle into the year 2024, the effects of climate change on our environment continue to make headlines. However, we should be concerned about more than just wildfires, hurricanes, and rising temperatures. A less visible but equally alarming consequence of our warming world is the impact of spreading infectious diseases. Recently, a team of experts, including Dr. George R. Thompson from UC Davis and his colleagues from Harvard Medical School and Massachusetts General Hospital, conducted a study that sheds light on these pressing issues.

In their study, published in JAMA (Journal of the American Medical Association), the researchers highlight how the changing climate reshapes the behavior of pathogens, vectors, and even the animals carrying diseases. According to the study, one of the most noticeable effects has been on vector-borne diseases — illnesses transmitted by vectors like ticks and mosquitoes. Due to shorter winters and extended summer seasons, ticks become active earlier and for longer periods each year. This means diseases like Lyme disease, traditionally associated with late spring and summer, are now a concern nearly year-round.

Mosquitoes need water to breed and are exceptionally sensitive to environmental conditions. As temperatures rise, mosquito breeding cycles become more efficient, leading females to seek more “blood meals” to support their eggs. This shift has facilitated the spread of diseases such as Zika and dengue fever, with Aedes aegypti mosquitoes pushing further north than ever before, introducing these diseases to new regions in the United States.

But it’s not only the tiny creatures we need to worry about. Larger animals, particularly those involved in zoonotic diseases (diseases transmitted between animals and humans), are also on the move. Changing weather patterns affect the availability of food and habitats for these animals, pushing them closer to human populations and increasing the risk of disease transmission. The recent uptick in cases of hantavirus and plague (yes, the famous medieval disease) in the western United States is a stark reminder of these dynamic shifts. Rodents spread both diseases.

Another alarming trend is the rise in fungal infections. Human body temperature is a barrier to many fungal pathogens, which cannot thrive at higher temperatures. However, as global temperatures inch closer to human body temperature, fungi are adapting. The emergence of pathogens like Candida auris, a highly resistant fungus first identified in 2009, is a scary example of what may become more common in a warmer world.

Climate change is also helping waterborne diseases to thrive. Rising sea levels and more frequent and severe flooding lead to increased exposure to pathogens like Vibrio, a flesh-eating bacteria that causes severe illness and can be fatal (google Vibrio infection only if you have the stomach for these types of images). The aftermath of Hurricane Ian in 2022, which resulted in numerous cases of vibriosis in Florida, underscores the direct impact of extreme weather events on human health.

What does all this mean for us? First and foremost, the medical community is sounding the alarm that they need to be prepared for these shifts. Improved surveillance and diagnostic techniques are crucial in managing the evolving landscape of infectious diseases. Moreover, as noted by Dr. Thompson and his team, there is an urgent need for educational updates within the medical field to keep healthcare providers informed and ready to tackle these challenges.

However, the responsibility doesn’t just lie with the medical professionals. Supporting policies that reduce greenhouse gas emissions and understanding the connection between our actions and their impact on the planet are steps we must take to help lessen the broader effects of climate change.

The situation may seem daunting, but we can take action. We can tackle these emerging health threats head-on with informed strategies and collective action. As Dr. Matthew Phillips aptly says, “It’s not a hopeless situation. There are distinct steps that we can take to prepare for and help deal with these changes.” As the planet continues to warm, staying informed and proactive is our best defense.