6.2.1: Case Study- COVID-19
Let’s use a recent example of a pandemic - which is a worldwide outbreak of a specific infectious disease. In 2019, a novel (new) virus, SARS-CoV-2, was discovered that caused an acute respiratory disease, which was named COVID-19. The agent in this case was SARS-CoV-2, the host was humans (although the virus was originally thought to come from bats, which would also make it a zoonotic disease with bats being the reservoir), and the environment was any place where aerosols (tiny air droplets containing the virus) could be transmitted from an infected person to others. Strategies to prevent the spread and reduce the harmfulness of the disease could be taken at different points on the triangle, and even at the interactions between two points. For example, one strategy to reduce community spread that addresses the risk of the host (agent-host interaction) is vaccination. If the host has developed acquired immunity to the virus, it is less likely that they will experience significant illness. Another community strategy that interrupts the environment-host interaction is social distancing or gathering outdoors in open air, which dilutes aerosols and increases the distance the infected air must travel to reach others. Yet another strategy to create a less hospitable environment for the virus is to wear masks or increase airflow and filtration. Hospitals were particularly concerned about these measures since many people with severe COVID-19 were being treated in hospital settings, and the medical process of intubation (performed on the sickest) releases a lot of viral aerosols into the air. See Fig. \(\PageIndex{1}\) for an adaptation of the epidemiological triangle as applied to COVID-19 and hospital procedures (like intubation).