Disease has been top-of-mind for weeks now, and Civil Beat readers have been asking how climate change will affect the spread of diseases — from the flu to dengue fever — in Hawaii. The latest episode of “Are We Doomed?,” our Q&A environmental podcast, puts those questions to an expert.

Unlike most of the country, Hawaii has a year-round flu season, partially because of our large number of visitors but also due to the tropical climate.

“Humidity has differing effects on flu survival outside the body depending on what the temperature is,” said Marta Shocket, a researcher studying how temperature affects the spread of disease at the University of California at Los Angeles. “Cold, dry environments are really good for the flu but if it’s warm year-round, humidity actually helps flu survive.”

Which is why there’s no guarantee that higher yearly temperatures due to climate change will limit the spread of flu.

Climate change could actually lead to more flu transmissions.

Researchers from Arizona State University analyzed flu seasons from 1997 to 2013 and found that large flu outbreaks followed mild winters.

“It appears that fewer people contract influenza during warm winters, and this causes a major portion of the population to remain vulnerable into the next season, causing an early and strong emergence,” wrote the authors. “And when a flu season begins exceptionally early, much of the population has not had a chance to get vaccinated, potentially making that flu season even worse.”

Additionally, our immune systems are weaker during heat waves, and we’re more vulnerable to the flu during dramatic changes in weather, like in a sudden cold snap.

Scientists don’t yet know how changing seasons will impact the spread of COVID-19, but preliminary research found that the coronavirus was less sensitive to changes in temperature than the yearly flu, Shocket said.

“It’s really unclear right now how big of an effect that might have,” Shocket said.

Climate change has also already affected the spread of mosquitoe-borne illnesses in Hawaii. Historically mosquitoes, and the diseases they carry, couldn’t thrive at high elevations because it was too cold.

But as temperatures creep up, mosquitoes gain territory. There’s already been disastrous effects on native bird populations that live high in the mountains to escape mosquitoes.

“If the mosquitoes can be successfully transmitting disease all the way up the mountain, then those birds will no longer have a cold-weather refuge,” Schocket said.

And as those mosquitoes make their way into higher elevations, there are more opportunities for humans to catch mosquitoe-borne illnesses like zika, dengue and ross river virus.

The burning of fossil fuels causes climate change and also pollutes the air, which can cause chronic conditions like asthma, heart disease and lung cancer.

“If carbon emissions are making it tough to be healthy and resilient out of the gate it makes us more susceptible to a pandemic or other illnesses … especially respiratory illnesses and that’s what COVID-19 is,” said Josh Stanbro, Honolulu’s chief resilience officer.

“Every day that we put off dealing with it exponentially ramps up the costs, how many people are affected and the impact to our economy,” Stanbro said. “This is true of climate change and this coronavirus.”

“The analogy between COVID-19 and climate is really glaring in terms of the disaster that awaits us if we don’t respond quickly,” he said.

“Are We Doomed? And Other Burning Environmental Questions” is funded in part by grants from the Environmental Funders Group of the Hawaii Community Foundation and the Frost Family Foundation.

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