A virus affecting wood frog tadpoles throughout the eastern United States is offering scientists a rare opportunity to investigate the role of environmental factors in the spread of infectious disease.
An important aspect of controlling the spread of any virus is understanding how the virus, or agent, is transmitted through the environment to the host. Scientists refer to the trio of agent, host, and environment as the epidemiological triangle or triad. In the COVID-19 pandemic, the agent is the SARS-CoV-2 virus, humans are the host species, and the environment now includes ecosystems throughout the planet. Scientists have made strides in understanding the nature of the SARS-CoV-2 virus and the infection it causes in its human hosts, and they have identified variables in the host population that can cause some individuals to be more severely affected by the virus than others. As researchers continue to learn about environmental factors that facilitate the spread of COVID-19, we practice social distancing and wear masks to contain airborne droplets from our mouths and noses.
The interrelationships among agent, host, and environment are complex, and possible variables in each of the three are limitless, making it impossible, when studying them as a system, to tease out the differential effects of the individual players. While agent and host can be studied in isolation and in direct relationship to each other within the laboratory, environmental factors also play a role in disease dynamics, meaning that any conclusions reached will not fully reflect that happens in natural systems. However, Associate Professor Tracy Rittenhouse has developed an experimental model where the focus is the effects of the environment in epidemics rather than the details of the agent and host interaction.
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