Climate change is affecting our very lives right now, with a depth and breadth that is truly astounding and unexpected. My colleagues and I were first struck by the impact of climate on infectious diseases way back in 2007 when we did a survey of West Nile Virus (WNV) throughout the United States. We assessed whether daily average temperatures, humidity, and/or rainfall -- events predicted by climate scientists to increase alongside global warming -- were associated with spikes in locally reported WNV cases. The analysis involved 16,000 cases (that's right, there were that many cases reported to the CDC back then) and showed a resounding association with weather-related events.

"My colleagues and I were first struck by the impact of climate on infectious diseases way back in 2007 when we did a survey of West Nile Virus (WNV) throughout the United States."

This should alarm you. It certainly frightens me -- a doctor -- and the more I learn about climate change, the more concerned I become. In our study, warmer temperatures, elevated humidity, and heavy precipitation increased the rate of human WNV infection in the US, independent of season. At a detailed level, prior studies have shown that increased heat enhanced WNV replication within mosquitoes, thereby increasing the infectious potential of each bite. Heat, humidity, and precipitation also led to increased reproduction, expanding the number of mosquitoes in a given area. Now, there's new evidence that these same factors have expanded the geographic area where mosquitoes in the US live. And that is really bad.

"In our study, warmer temperatures, elevated humidity, and heavy precipitation increased the rate of human WNV infection in the US, independent of season."

Mosquitoes, of which there are many species, are responsible for the transmission of several incurable human diseases. West Nile Virus is among those for which fully effective vaccines do not exist, as are: St. Louis Encephalitis, Zika, and Dengue. Climate change -- as seen by the tropicalization of the continental US -- may result in new vector species (carriers) and cause the spread of other infectious diseases. For example, the Reduviid bug ("kissing bug"), is the carrier for Chagas Disease (a parasitic infection) throughout Latin America. This disease -- which most patients don't know they have until they suffer irreversible heart damage -- is exceedingly difficult to treat. As a cardiologist at Olive View - UCLA Medical Center in Los Angeles, I'm part of a division that runs a clinic specifically devoted to Chagas, a disease we're seeing with persistent and increasing frequency. In the last large epidemiological study we published, the local Los Angeles community demonstrated a 1.3% rate of infection -- well above estimates previously reported.

"Mosquitoes, of which there are many species, are responsible for the transmission of several incurable human diseases. West Nile Virus is among those for which fully effective vaccines do not exist, as are: St. Louis Encephalitis, Zika, and Dengue."

Many Americans used to live with the sense that modern medical science could quickly and easily stop the spread of infectious diseases that cross our borders. COVID-19 has squarely dispelled this belief and further revealed that human behavior -- what we do and how we act to prevent disease spread -- is paramount to protecting ourselves and our families' lives.

"Many Americans used to live with the sense that modern medical science could quickly and easily stop the spread of infectious diseases that cross our borders."

Climate change is not just about sea-level rise, storms, or the polar ice melt. It's not just about the big, visible events. COVID-19 reminds us, even things we can't see can be extremely deadly or disruptive. As seen in the aforementioned study of the West Nile Virus, the effects of climate change are impacting our lives and health on a microscopic level that often goes undetected until it's too late. If we don't want to see waves of infectious, and often incurable diseases crash upon our hospitals the way COVID-19 has, we must prevent their spread by addressing and reversing climate change now.

"...we cannot let what has happened with covid -- the disarray and dispute over basic science and consensus-driven approaches -- happen with climate change."

As tired as we all are after a long 2020, we cannot let what has happened with covid -- the disarray and dispute over basic science and consensus-driven approaches -- happen with climate change. There will never be a vaccine for global warming. It profoundly and irreversibly alters everything from the smallest microbe and mosquito to our oceans and our survival.