Bite Fright

How will climate change affect human health in the Southwest?

Kacey Ernst, associate professor of epidemiology and biostatistics in the UA Mel and Enid Zuckerman College of Public Health, studies how climate change is affecting human health, including recent concerns about the mosquito-borne Zika virus. She's the next speaker in the UA College of Science spring lecture series, "Earth Transformed." Ernst will discuss "Climate Change and Human Health: Impacts and Pathways to Resilience" at 7 p.m. Monday, Feb. 22, at UA Centennial Hall. The talk is free. For more info, visit

Your work has been studying how climate change may impact human health from a global standpoint. What are some of the impacts you have been seeing based on the climate change?

There's nobody who can escape the effects of climate change, really. And some of the things that we will see are increasing food and water insecurity. And those are all sort of fundamental building blocks to people's health. If you don't have enough good nutrition, if you don't have access to clean water, that can really affect your health status. But then, there are things that are a little more indirect, like increasing range of vectors that transmit infections. A vector would be something like a mosquito or a tick. They may be expanding their range and putting people at risk that weren't at risk before. Also, there's the direct impact of increasing extreme weather events. As you have more flooding events, if you have other something like extreme heat events, those also have direct health impacts on individuals. In your talk on Monday, Feb. 22, you'll be focusing on the impact in the Southwest United States. Much depends on what happens in terms of reducing carbon emissions, but can you talk a little bit about best-case scenarios vs. worst-case scenarios?

I think what we know, now, is that it is going to get hotter. Here in this region, it is going to get drier, and then the precipitation events are going to be a little more extreme, so when we do get rainfall, we will get a more sort of heavier rainfall, and so this coupling of less water but more extreme water events in addition to higher extreme heat—those are some of the climatic things that we will be facing.

Talk about some of the impacts that increase increased heat has on human health.

We live in a hot climate already and if you are directly exposed, it can exacerbate health problems that you already have. So people who have cardiovascular disease are more likely to have a cardiac event when it's extremely hot. Individuals who are out working in the sun may have a heat stroke, so there are those real, direct impacts that can occur. Also, when you have drought, you have a higher risk of wildfire, and when you have wildfires, that influences the air quality, and if the air quality is poor, that can trigger asthma attacks in people and other health effects.

One important element of this is your work with mosquitos and the risk of virus transmission. What do we have to worry about? We have Aedes aegypti mosquitos. It was here, historically for many decades. Then there was a huge sort of campaign throughout Latin America to eliminate the mosquitos but it resurged. In 1998, we first recognized sort of that re-establishment of Aedes aegypti here. I have been wondering "Why are these darn mosquitos back?" It seems like they weren't here when I was younger.

Right. I think it's multiple factors One aspect may be climate change, but we also have a much higher mobility of our population. This mosquito can get introduced when you bring in imported gifts. Imported tires. Lucky bamboo has introduced Aedes species into California. So, there are many reasons that it can be introduced, but one of the things that is really sort of unique about Aedes aegypti is that they really love people. They like to be in domestic environments. So if you have a lot of containers in your back yard, these are container breeders. The plates that you put under a flower pot—if you don't drain it regularly, they can lay their eggs right in that little basin of water underneath your flower pot and go through their life cycle until they become an adult right in that area and so, any time you have increased plastic containers or things like that in your back yard, it's going to really increase their habitat How long do some of these mosquitos live? They have their season, but how long do the individual bugs live?

The average mosquito lives about three weeks, give or take. It really depends on climate conditions. If it gets really hot, it actually decreases their survival, but they're very adaptable mosquitos, and they, just like people, will find those little niches and microclimates, as we call them, that are cool and more moist and then they sort of hunker down and survive longer And what are some of the steps we can take to reduce these risks?

One public health message that I would love to see get out there is that people make it a habit to use mosquito repellant as often as they do sunscreen here in this area. A lot of people, when we surveyed them in Tucson, don't like to use the repellant, but there are some repellants that you can use that you can apply to your clothing, etc., and you don't have to apply directly to your skin. Empty out that standing water. A lot of those messages that you heard associated with West Nile Virus hold true here, too. Also, if you can cover up—although with that extreme heat you certainly don't want to cover up too much, because you would overheat. And reduce your immediate involvement in introducing habitat.

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