Not only is climate change affecting the environment, it is also affecting human health. Two of the main factors associated with climate change are annual average temperature and annual average precipitation. As the earth continues to warm and more intense precipitation events occur, insects, such as mosquitoes, are expected to be an even greater risk to human health. Within the continental United States, “West Nile virus is the leading cause of mosquito-borne diseases”. However, it is unknown whether the rate of West Nile virus will increase as the mosquito population is predicted to increase.
For this study, I tested the association between annual average temperature and annual average precipitation in Indiana, Ohio, Illinois, Kentucky, and Missouri because they are part of the Ohio Valley Climate Region. My research question is “How will the effects of climate change affect the rate of West Nile virus in five states in the Ohio Valley Climate Region?” I hypothesize that the effects of climate change (i.e., an increase in annual average temperature and annual average precipitation) will increase the rate of West Nile virus.
After collecting data from the National Oceanic and Atmospheric Administration and Centers for Disease Control and Prevention’s websites, regressions in Microsoft Excel were used to measure the strength and direction of the relationship between independent and dependent variables. I performed two regressions for each state – one for annual average temperature vs West Nile virus human cases and one for annual average precipitation vs West Nile virus human cases. I used a 95% confidence level for each regression.
For a 1-degree change in annual average temperature, there is an associated increase of 10 additional West Nile virus cases in Indiana between 2001-2021. There is an associated increase of 11 additional West Nile virus cases in Ohio. Illinois had the largest associated increase of West Nile virus cases, with a total of 38. In Kentucky, a 1-degree change in annual average temperature between 2001-2021 is associated with an increase of 3 West Nile virus cases. After performing a regression with the X variable of annual average temperature for each state for the years 2001-2021, it was found that Missouri has the lowest associated increase in West Nile virus cases, with a coefficient of <1 (0.79).
Within the same time frame of 20 years, there is an associated decrease of 2 cases of West Nile virus for a 1-inch change in annual average precipitation in Indiana. Regarding the 1-inch change in annual average precipitation in Ohio from 2001-2021, there is an associated decrease of 2 cases of West Nile virus. There is an associated decrease of 12 West Nile virus cases for a 1-inch change in annual average precipitation is Illinois. For a 1-inch change in annual average precipitation in Missouri between 2001-2021, there is an associated decrease of 2 West Nile virus cases. Unlike the other four states, there is an associated increase of <1 (0.12) West Nile virus cases in Kentucky.
After conducting this study, it is evident that West Nile virus is a cause for concern since every state saw an increase in cases, whether looking at the annual average temperature or annual average precipitation. In order to get a more accurate estimate of the rate of West Nile virus, other factors of climate change should be analyzed. In general, this means that we, as individuals, need to ensure we are taking preventative measures to try to reduce our risk of getting West Nile virus – such as using insect repellent, wearing long-sleeved shirts and pants, and taking steps to control mosquitoes both indoors and outdoors. Not only do we have to take preventative measures to prevent the spread of West Nile virus, we also need to address the root of the problem: climate change.
Regan Margerum is a junior in the O’Neill School of Public and Environmental Affairs majoring in Environmental Science with minors in Water Resource Science, Policy, and Management and also in Outdoor Recreation, Parks, and Human Ecology.
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