Pandemics are a lot like wildfires—first they spark, and then they spread. New infectious diseases can arise from anywhere. They are often triggered by human activities such as changes in land use or agriculture. Once a new disease emerges, it can spread quickly, pushed along by human travel and commerce.
The virus that causes COVID-19 was first identified in China in December 2019. Because of its unique characteristics and our interconnected society, the virus rapidly spread across the globe.
COVID-19 is a disease caused by a virus called SARS-CoV-2. The virus enters our bodies through the nose and mouth and attacks our cells to make copies of itself. People with COVID-19 feel symptoms like fever, cough, and shortness of breath as the virus replicates and the immune system fights back.
Not all infectious diseases cause pandemics. But COVID-19's balance of contagiousness and deadliness helped it spread quickly, with dire consequences.
COVID-19 shares similarities with the 1918 flu, the virus that caused the last major pandemic.
